CN118251745A - Charged particle apparatus and method - Google Patents

Abstract

The present disclosure relates to a charged particle beam apparatus configured to project a charged particle beam towards a sample. The charged particle beam apparatus comprises a plurality of charged particle optical columns configured to project respective charged particle beams towards a sample, wherein each charged particle optical column comprises: a charged particle source configured to emit a charged particle beam towards the sample, the charged particle source being included in the source array; an objective lens comprising an electrostatic electrode configured to direct a sample towards a charged particle beam; and a detector associated with the objective lens array, the detector configured to detect a charged particle signal emitted from the sample. The objective lens is the beam downstream-most element of the charged particle optical column configured to affect the charged particle beam directed towards the sample.

Description

Charged particle apparatus and method

Cross Reference to Related Applications

The present application claims priority from EP application 21178234.7 filed on 8 th year 2021, EP application 21184290.1 filed on 7 th year 2021, and EP application 21217745.5 filed on 24 th year 2021, which are incorporated herein by reference in their entirety.

Technical Field

Embodiments provided herein relate generally to charged particle beam apparatuses and methods of using the same.

Background

When manufacturing semiconductor Integrated Circuit (IC) chips, undesirable pattern defects inevitably occur on a substrate (i.e., wafer) or mask during the manufacturing process due to, for example, optical effects and the consequences caused by incidental particles, thereby reducing yield. Therefore, monitoring the extent of undesired pattern defects is an important process in manufacturing IC chips. More generally, inspection and/or measurement of the surface of a substrate or other object/material is an important process during and/or after the manufacture of the substrate or other object/material.

Pattern inspection tools having charged particle beams have been used to inspect objects, for example, to detect pattern defects. These tools typically use electron microscopy techniques such as Scanning Electron Microscopy (SEM). In SEM, a primary electron beam of relatively high energy electrons is targeted at a final deceleration step in order to land on the sample with a relatively low landing energy. The electron beam is focused as a probe spot on the sample. Interactions between the material structure at the detection spot and landing electrons from the electron beam cause electrons such as secondary electrons, backscattered electrons or auger electrons to be emitted from the surface. The generated secondary electrons may be emitted from the material structure of the sample. By scanning the primary electron beam as a probe spot over the surface of the sample, secondary electrons can be emitted across the surface of the sample. By collecting these secondary electrons emitted from the surface of the sample, an image can be obtained that represents the characteristics of the material structure of the surface of the sample.

The pattern inspection tool is provided with a source of electron beams. Such a source is characterized by an emitter that emits a beam of electrons. In general, there is a need for improved combinations of brightness, total current and current stability that reduce the source of the electron beam.

Disclosure of Invention

It is an object of the invention to improve the combination of reduced brightness, total current and current stability of an electron beam.

According to one aspect of the present invention there is provided a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a plurality of charged particle optical columns arranged in an array of charged particle optical columns configured to project respective charged particle beams towards the sample, wherein each charged particle optical column comprises a plurality of charged particle emitters configured to emit charged particle beams towards the sample, the charged particle emitters being comprised in a source array; and preferably an objective lens configured to direct a charged particle beam towards the sample, the objective lens being an electrostatic objective lens, the objective lens being comprised in an objective lens array; wherein the charged particle emitters are configured to be selectable such that a subset of the charged particle emitters may be selected to emit a charged particle beam towards the sample.

Drawings

The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments, which is to be read in connection with the accompanying drawings.

Fig. 1 is a schematic diagram illustrating an exemplary electron beam inspection device.

Fig. 2 is a schematic diagram illustrating an exemplary charged particle beam apparatus as part of the exemplary charged particle beam inspection apparatus of fig. 1.

Fig. 3 is a schematic diagram of a charged particle multi-beam column comprising a collimator array.

Fig. 4 is a schematic diagram of a charged particle multi-beam column array including the multi-beam column of fig. 3.

Fig. 5 is a schematic plan view of a rectangular multi-beam column array.

Fig. 6 is a schematic side cross-sectional view of a portion of an electrode forming a deceleration objective in a multi-beam column having an array of beam downstream apertures.

Fig. 7 is a schematic enlarged top cross-sectional view showing the apertures in the beam downstream aperture array relative to plane A-A in fig. 6.

Fig. 8 is a schematic side cross-sectional view of an electronic detection device integrated with a three-electrode objective lens array.

Fig. 9 is a bottom view of a detector module of the type depicted in fig. 8 or 12.

Fig. 10 depicts a portion of a detector module in cross-section.

Fig. 11 is a schematic side cross-sectional view of an electron detection device located in a beam downstream surface of a beamlet-defining aperture array.

Fig. 12 is an end view of the beam downstream surface of the beamlet-defining aperture array of fig. 11.

Fig. 13 is a schematic diagram illustrating a column array.

Fig. 14 is a schematic diagram illustrating a column array.

Fig. 15 is a schematic diagram illustrating the sources of the source array of pillars.

Fig. 16 is a schematic diagram illustrating a pillar pattern of a pillar array.

Fig. 17 is a schematic diagram illustrating the pillar array of fig. 13 operating in a different manner.

Fig. 18 is a schematic diagram illustrating the column array of fig. 14 operating in a different manner.

Fig. 19 is an end view of the beam downstream surface of the post array.

Fig. 20 is an end view of the beam downstream surface of the column array.

Fig. 21 is a schematic diagram illustrating a column array.

Fig. 22 is a schematic diagram of an embodiment of a pillar array, for example, according to the embodiment depicted in fig. 19 or 20.

Detailed Description

Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements, unless otherwise indicated. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with aspects related to the invention as set forth in the following claims.

The enhanced computational power of electronic devices can be achieved by significantly increasing the packing density of circuit components such as transistors, capacitors, diodes, etc. on an IC chip, which reduces the physical size of the device. This has been achieved by increasing the resolution so that smaller structures can be made. For example, the IC chip of a thumb nail sized smart phone available in 2019 or earlier may include over 20 hundred million transistors, each transistor having a size less than 1/1000 of human hair. Thus, not surprisingly, semiconductor IC fabrication is a complex and time-consuming process with hundreds of individual steps. Even errors in one step can greatly affect the functionality of the final product. Only one "fatal defect" can lead to equipment failure. The goal of the manufacturing process is to increase the overall yield of the process. For example, to achieve 75% yield for a 50 step process (where steps may indicate the number of layers formed on a wafer), each individual step must have a yield of greater than 99.4%. If the yield of the individual steps is 95%, the overall process yield will be as low as 7%.

While high process yields are desirable in IC chip manufacturing facilities, it is also essential to maintain high substrate (i.e., wafer) yields, which are defined as the number of substrates processed per hour. The presence of defects can affect high process yields and high substrate yields. This is especially true in situations where operator intervention is required to inspect the defect. Therefore, high-throughput inspection and identification of micro-scale and nano-scale defects by inspection tools such as scanning electron microscopes ("SEM") is essential to maintaining high yields and low costs.

The SEM includes a scanning device and a detector arrangement. The scanning device comprises an illumination means comprising an electron source for generating primary electrons and a projection means for scanning a sample, such as a substrate, using one or more primary electron focused beams. At least the illumination device or illumination system and the projection device or projection system may together be referred to as an electron optical system or device. The primary electrons interact with the sample and generate signal electrons. While scanning the sample, the detection device captures signal electrons from the sample so that the SEM can produce an image of the scanned area of the sample. For high throughput inspection, some inspection devices use multiple focused beams of primary electrons, i.e., multiple beams of primary electrons. The component beams of the multiple beams may be referred to as sub-beams or sub-beam waves. Multiple beams may scan different portions of the sample simultaneously. Thus, the multi-beam inspection apparatus is capable of inspecting a sample at a much higher speed than a single-beam inspection apparatus.

The following figures are schematic. Accordingly, the relative dimensions of the components in the drawings are exaggerated for clarity. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and only differences with respect to the individual embodiments are described. While the description and drawings relate to an electron optical apparatus, it should be appreciated that these embodiments are not intended to limit the disclosure to particular charged particles. Thus, references to electrons in this document may be more generally considered to be references to charged particles, which are not necessarily electrons.

Referring now to fig. 1, fig. 1 is a schematic diagram illustrating an exemplary electron beam inspection device 100. The electron beam inspection device 100 of fig. 1 includes a main chamber 10, a load lock chamber 20, an electron beam device 40 (which may be referred to as an electron beam tool), an Equipment Front End Module (EFEM) 30, and a controller 50. An electron beam device 40 is located within the main chamber 10.

The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional load port(s). For example, the first load port 30a and the second load port 30b may receive a front opening wafer box (FOUP) containing a substrate (e.g., a semiconductor substrate or a substrate made of other material (s)) or a sample to be inspected (the substrate, wafer, and sample are hereinafter collectively referred to as "samples"). One or more robotic arms (not shown) in the EFEM 30 transport samples to the load lock chamber 20.

The load lock chamber 20 is used to remove gas from around the sample. This creates a vacuum, i.e. the partial gas pressure is lower than the pressure in the surrounding environment. The load lock chamber 20 may be connected to a load lock vacuum pump system (not shown) that removes gas particles from the load lock chamber 20. The operation of the load lock vacuum pump system enables the load lock chamber to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) transfer the sample from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas particles in the main chamber 10 so that the pressure around the sample reaches a second pressure lower than the first pressure. After reaching the second pressure, the sample is transported to an electron beam device 40, which can inspect the sample. The electron beam device 40 may comprise a multi-beam device.

The controller 50 is electrically connected to the electron beam device 40. The controller 50 may be a processor (such as a computer) configured to control the charged particle beam inspection device 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. Although the controller 50 is shown in FIG. 1 as being external to the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, it should be appreciated that the controller 50 may be part of the structure. The controller 50 may be located in one of the constituent elements of the electron beam inspection device 100 or it may be distributed over at least two of the constituent elements.

Referring now to fig. 2, fig. 2 is a schematic diagram illustrating an exemplary electron beam apparatus including as part of the exemplary charged particle beam inspection apparatus 100 of fig. 1. The electron beam device 40 may include an electron source 199, a projection device 230, a motorized stage 209, and a sample holder 207. In one embodiment, a plurality of electron sources 199 are provided. Together, electron source 199 and projection device 230 may be referred to as an electron-optical device. The sample holder 207 is supported by a motorized stage 209 to hold a sample 208 (e.g., a substrate or mask) for inspection. The electron beam apparatus 40 may further comprise an electron detection device 240.

Electron source 199 may include a cathode (not shown) and an extractor or anode (shown in fig. 9). Electron source 199 may be configured to emit electrons from the cathode as primary electrons. The primary electrons are extracted or accelerated by an extractor and/or anode to form an electron beam 202 comprising the primary electrons.

The projection device 230 is configured to convert the electron beam 202 into a plurality of sub-beam waves 211, 212, 213 and to direct each sub-beam wave onto the sample 208. Although three sub-beam waves are illustrated for simplicity, there may be tens, hundreds, or thousands of sub-beam waves.

The controller 50 may be connected to various portions of the electron beam inspection device 100 of fig. 1, such as the electron source 199, the electron detection device 240, the projection device 230, and the motorized stage 209. The controller 50 may perform various image and signal processing functions. The controller 50 may also generate various control signals to govern the operation of the electron beam inspection device 100, including the electron beam device.

The projection device 230 may be configured to focus the sub-beam waves 211, 212, and 213 onto the sample 208 for inspection, and may form three probe spots 221, 222, and 223 on the surface of the sample 208. Projection device 230 may be configured to deflect sub-beam waves 211, 212, and 213 to scan probe spots 221, 222, and 223 across individual scan areas in a section of the surface of sample 208. Such scanning may include electrostatic manipulation by electrostatic deflectors in the electron optical column, as well as movement of the stage to move the sample surface beneath the probe spot to cause the spot to scan the sample surface. Electrons may be generated from the sample 208 in response to the sub-beam waves 211, 212, and 213 being incident on the detection spots 221, 222, and 223 on the sample 208, which may include signal electrons such as secondary electrons and backscattered electrons. The electron energy of the secondary electrons is typically 50eV or less. The electron energy of the backscattered electrons is typically between 50eV and the landing energy of the beamlet waves 211, 212 and 213.

The electronic detection device 240 may be configured to detect signal electronics and generate corresponding signals that are sent to the controller 50 or a signal processing system (not shown), for example, to construct an image of a corresponding scanned region of the sample 208. The electronic detection device 240 may be incorporated into the projection apparatus 230 or may be separate from the projection apparatus 230, wherein a secondary optical column is provided to direct signal electrons to the electronic detection device 240.

The controller 50 may include an image processing system including an image acquirer (not shown) and a storage device (not shown). For example, the controller 50 may include a processor, computer, server, mainframe, terminal, personal computer, any kind of mobile computing device, etc., or a combination thereof. The image acquirer may include at least a portion of the processing functionality of the controller. Thus, the image acquirer may include at least one or more processors. The image acquirer may be communicatively coupled to an electronic detection device 240 of the electron beam apparatus 40 that permits signal communication, such as an electrical conductor, a fiber optic cable, a portable storage medium, IR, bluetooth, the internet, a wireless network, a radio, or the like, or a combination thereof. The image acquirer may receive the signal from the electronic detection device 240, may process the data included in the signal, and may construct an image therefrom. Thus, the image acquirer can acquire an image of the sample 208. The image acquirer may also perform various post-processing functions, such as generating contours, superimposing indicators on the acquired image, and the like. The image acquirer may be configured to perform adjustment of brightness, contrast, and the like of the acquired image. The storage device may be a storage medium such as a hard disk, flash drive, cloud storage, random Access Memory (RAM), other types of computer readable memory, and the like. A storage device may be coupled to the image acquirer and may be used to save scanned raw image data as raw images and post-processed images.

The image acquirer may acquire one or more images of the sample based on the imaging signals received from the electronic detection device 240. The imaging signal may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image including a plurality of imaging regions. The single image may be stored in a storage device. A single image may be an original image that may be divided into a plurality of partitions. Each of the partitions may include an imaging region containing features of the sample 208. The acquired images may include multiple images of a single imaging region of the sample 208 that are sampled multiple times over a period of time. The plurality of images may be stored in a storage device. The controller 50 may be configured to perform the image processing steps using multiple images of the same location of the sample 208.

The controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain a distribution of detected charged particles (e.g., signal electrons). Charged particle (e.g., electron) distribution data collected during the detection time window may be used in combination with corresponding scan path data for each of the sub-beam waves 211, 212, and 213 incident on the sample surface to reconstruct an image of the sample structure under inspection. The reconstructed image may be used to reveal various features of an internal structure or an external structure of the sample 208. Thus, the reconstructed image may be used to reveal any defects that may be present in the sample.

The controller 50 may control the motorized stage 209 to move the sample 208 during inspection of the sample 208. At least during sample inspection, the controller 50 can cause the motorized stage 209 to move the sample 208 in a scanning direction (preferably continuously), e.g., at a constant speed. The controller 50 can control the movement of the motorized stage 209 such that it varies the speed of movement of the sample 208 in accordance with various parameters. For example, the controller 50 may control the stage speed (including its direction) in accordance with the nature of the inspection step of the scanning process.

Fig. 3 depicts an electron beam column 110. The electron beam column 110 may be provided as part of an electron beam device that projects multiple beams of electrons toward the sample 208; for this reason, the electron beam column 110 may be referred to as a multi-electron beam column 110. The electron beam device may include any of the features of the electron beam device 40 discussed above with reference to fig. 2. Associated with each electron beam column 110 is an electron source 199 that emits an electron beam 112. (the electron beam column 110 may also be considered to include an electron beam source 199, but since the array of sources may be in a separate module from the column, such sources may be separate from the associated column. In some embodiments, charged particles other than electrons are used in place of electrons. Electron source 199 may be configured in any of the ways described above with reference to fig. 2. Electron source 199 may include a cathode (not shown) and may provide an extractor or anode (not shown). Electron source 199 may comprise a high brightness emitter having a desirable balance between reduced brightness and total emission current. The brightness of the characteristic degradation takes into account the energy spread of the emitted electrons. In one arrangement, there are multiple electron sources. Electron source 199 is one of a plurality of electron sources. The plurality of electron sources forms an array of sources and is referred to as a source array. In the source array, the sources may be provided on a common substrate.

The electron beam column 110 includes a beamlet-defining aperture array 152 (e.g., comprising a plate-like body having a plurality of apertures). The beamlets define a beam-forming beamlet of electrons 122 emitted by the electron source 100 by the aperture array 152. However, it is not essential to provide a beamlet-defined aperture array. In one embodiment, the electron beam column 110 is configured to project a single beam toward the sample 208.

In one embodiment, electron beam column 110 includes collimator array 150. The collimator array 150 includes a plurality of collimators. Three collimators are shown in fig. 3. In an alternative embodiment, each electron beam column 110 includes a single collimator of collimator array 150. When a beamlet-defining aperture array 152 is provided, the collimator array 150 is downstream of the beamlets of the beamlet-defining aperture array 152. The collimators are each configured to collimate a respective beamlet. The collimator array 150 forms collimated sub-beam waves from the emitted electrons 112.

The beamlet-defining aperture array 152 may be directly adjacent to and/or integrated with the collimator array 150. Each of the collimators in the collimator array 150 may be a deflector, and may be referred to as a collimator deflector.

The electron beam column 110 further comprises an objective lens array 118, which objective lens array 118 comprises a plurality of objective lenses. Three objectives are shown in fig. 3. In an alternative embodiment, each electron beam column 110 includes a single objective lens (which may include multiple electrodes) of objective lens array 118. The path of the electrons is schematically depicted by the dashed lines in fig. 3, and it can be schematically seen that the collimator deflects the electrons such that the beamlets are incident substantially normal to the objective lens and then to the sample 208. The objectives of the objective array 118 may be in a common plane. Each objective lens projects a collimated sub-beam onto the sample 208. The distance from electron source 199 to each objective lens is selected to provide the desired demagnification. Collimation may reduce field curvature effects at the objective lens, thereby reducing errors caused by field curvature, such as astigmatism and focus errors. In this embodiment, the collimator array 150 is not disposed in the intermediate image plane relative to the array of converging lenses. This may increase the chromatic aberration, thereby increasing the minimum size of the illuminated spot on the sample 208. However, the area illuminated by each electron source 199 may be relatively small, and thus any increase in the minimum size of the illuminated spot due to chromatic aberration may be tolerated.

The objective lens array is herein schematically depicted by an elliptical array. Each oval represents one of the objectives in the objective array. Conventionally, an oval shape is used to represent a lens, similar to the biconvex form commonly employed in optical lenses. However, in the context of a charged particle arrangement such as the charged particle arrangement discussed herein, it should be understood that the objective lens array will typically operate electrostatically, and thus may not require any physical elements in the form of biconvex. That is, the objective lens is an electrostatic lens. The objective lens array may be an electrostatic lens array. The objective lens array may for example comprise at least two plates, wherein each plate has a plurality of holes or apertures. The position of each hole in a plate corresponds to the position of a corresponding hole in another plate. The same sub-beam of the multiple beams is operated upon when the corresponding aperture is in use.

The electron beam column 110 further comprises a detector 170. The detector 170 detects charged particles (e.g., signal electrons) emitted from the sample 208. The detector 170 is disposed in a plane downstream of the beamlets defining the aperture array 152. In some embodiments, as illustrated in fig. 3, the detector 170 is located in the beam-most downstream surface of the electron beam column 110 (e.g., facing the sample 208, when in use). In other embodiments, as illustrated in fig. 11 and 12 and as discussed below, the detector is located in a plane upstream of the beam of the objective array 118 or in a plane upstream of the beam of at least one electrode of the objective array 118. In the example discussed, the detector 170 is located in the beam downstream surface of the beamlet-defining aperture array 152.

In one embodiment, detector 170 comprises, for example, a CMOS chip detector integrated with a bottom electrode of one or more of the objectives of objective lens array 118. The detector 170 may be configured in any of the ways described above for the electronic detection device 240. The detector 170 may, for example, generate signals that are sent to the controller 50 or signal processing system, as described above with reference to fig. 1 and 2, for example, to construct an image of the region of the sample 208 scanned by the multi-beam column 110 or to perform other post-processing.

In the illustrated embodiment, each collimator in collimator array 150 is directly adjacent to one of the objectives in objective array 118. The collimator may be in direct contact with the objective lens or at a small distance from the objective lens (with or without any other elements in between). By being directly adjacent to the objective lens, the collimator and sub-beam defining aperture array 152 (which may be the first array element along the beam path from electron source 199) may be closer to sample 208 than alternative arrangements in which the collimator array is disposed further upstream of the beam (e.g., in an intermediate image plane associated with the converging lens array). Thus, the collimator array 150 and beamlet-defining aperture array 152 are closer to the objective lens and/or the sample 208 than the electron source 199. Ideally, the distance between beamlet-defining aperture array 152 and the objective lens is much smaller, preferably about 10 times smaller, than the distance from electron source 199 to beamlet-defining aperture array 152.

Bringing the collimator array 150 close to the sample 208 in this manner simplifies the requirements of charged particle optics upstream of the beam of the collimator array 150. For example, the requirements for the corrector to ensure that the beamlets enter the collimator and/or the objective lens with good alignment are less stringent (because the beamlets are formed directly upstream of the beam of the collimator and/or the objective lens and are thus in essence well aligned).

In some embodiments, as illustrated in fig. 3, the electron beam column 110 is configured such that electrons propagate from the electron source 199 to the beamlet-defining aperture array 152 without passing through any lens array or deflector array. Avoiding any lens or deflector array element upstream of the beam of collimator array 150 may mean that a smaller proportion of electrons from electron source 199 are directed through the objective lens, but the requirements for electron optics upstream of the beam of the objective lens and the corrector for correcting defects in such optics are reduced.

In an alternative embodiment, collimator array 150 is omitted. Omitting the collimator array 150 simplifies the overall arrangement and may allow the beamlet-defining aperture array 152 to be positioned closer to and/or integrated with the objective array.

In some embodiments, the yield is increased by using multiple electron sources 199. In some embodiments, as illustrated in fig. 4 and 5, a charged particle multi-beam column array is provided. The charged particle multi-beam column array may include any of the embodiments of the plurality of electron beam columns 110 described herein. Each electron beam column 110 forms a beamlet from electrons emitted by a different respective electron source 199. Each respective electron source 199 may be one of a plurality of electron sources 199. At least a subset of the plurality of electron sources 199 may be provided as a source array. The source array may include a plurality of electron sources 199 disposed on a common substrate. The electron beam columns 110 are arranged to project onto different sections of the same sample 208 simultaneously. Whereby an increased area of the sample 208 may be processed (e.g., evaluated) simultaneously. To achieve a small spacing between the electron beam columns 110, the objective lens array 118 and/or collimator array 150 of each electron beam column 110 may be fabricated using techniques used to fabricate microelectromechanical systems (MEMS) or by using CMOS technology. The electron beam columns 110 may be arranged adjacent to each other so as to project electron beamlets onto adjacent sections of the sample 208. In principle, any number of electron beam columns 110 may be used. Preferably, the number of electron beam columns 110 is in the range of 9 to 10000. In one embodiment, the electron beam columns 110 are arranged in a rectangular array, as schematically depicted in fig. 5. In an alternative embodiment, electron beam columns 110 are arranged in a hexagonal array. In other embodiments, the electron beam columns 110 are provided in an irregular array or a regular array having a geometry other than rectangular or hexagonal. When referring to a single electron beam column 110, each electron beam column 110 in the multi-beam column array may be configured in any of the ways described herein.

The beamlets of each electron beam column 110 may be scanned across a respective individual scanning region of the object plane in which the sample 208 is placed. That is, the sample surface is exposed to the beam spot of each beamlet. The sample surface exposed by each beam spot may be referred to as an addressable area. The addressable areas of all sub-beams of the electron beam column 110 may be collectively referred to as an array addressable area. Because the scan range of the beamlets is less than the pitch of the objective lens 118, the array addressable area may not be continuous. Successive sections of the sample 208 may be scanned by mechanically scanning the sample 208 in the object plane along the scan direction. The mechanical scan of the sample 208 may be a zig-zag or step-and-scan type movement. In one embodiment, the mechanical scan of the sample 208 is a continuous scan at a fixed speed.

The addressable area may be a circular partition or a polygonal partition. The partition is the smallest such shape that covers the addressable area. The partitions addressed by adjacent electron beam columns 110 are adjacent on the sample 208 when placed in the object plane. Adjacent partitions need not be contiguous. The electron beam column 110 may be arranged to cover at least a portion to all of the sample 208. These zones may be spaced apart so that the entire portion may be projected onto it by electron beam column 110. The stage may be moved relative to the electron beam column 110 such that the partition associated with the electron beam column 110 covers the entire portion of the sample 208 without overlapping. The footprint of the electron beam column 110 (i.e., the projection of the electron beam column 110 onto the object plane) is typically larger than the area of the electron beam column 110 onto which the beamlets are projected.

In any of the embodiments described herein, as illustrated in the embodiments of fig. 3 and 4, the electron beam column 110 may include one or more aberration correctors 126, the one or more aberration correctors 126 configured to reduce one or more aberrations in the beamlets incident on the sample 208. Each of the at least one subset of aberration corrector 126 may be integrated with or directly adjacent to one or more of the objectives in the objective lens array 118, or with or directly adjacent to one or more of the collimators in the collimator array 150 (if present). The aberration corrector 126 may be configured to apply one or more of the following to the beamlets: focus correction, field curvature correction, astigmatism correction. The correction may be applied to individual beamlets (e.g., where each beamlet potentially receives a different correction) or to groups of beamlets (e.g., where beamlets within each group receive the same correction for at least one type of correction). At least some of the groups may each consist of beamlets that are all within the same electron beam column 110. Alternatively or additionally, at least some of the groups may each include beamlets located in different electron beam columns 110 in the array of columns. Applying corrections in groups reduces the wiring requirements of the aberration corrector 126. The aberration corrector 126 may be implemented according to the description in european patent application number 20168281.2, which is specifically incorporated herein by reference for the disclosure of an aperture assembly and a beam manipulator unit for applying correction to a sub-beam.

In some embodiments, the array of posts includes a focus corrector. The focus corrector may be configured to apply a focus correction to each individual beamlet. In other embodiments, the focus corrector applies a group focus correction to each of a plurality of groups of multiple beams. Each group focus correction is the same for all sub-beams of the corresponding group. The focus correction may include any or all of the corrections in the Z direction, the Rx direction, and the Ry direction. As mentioned above, applying the correction by group may reduce wiring requirements. In some embodiments, the focus corrector applies different corrections to the beamlets from different electron beam columns 110. Thus, the focus correction applied to multiple beams from one electron beam column 110 may be different from the focus correction applied to multiple beams from different electron beam columns 110 in the same column array. Accordingly, the focus corrector can correct manufacturing differences or mounting differences between different electron beam columns 110 and/or surface height differences of the sample 208 between different electron beam columns 110. Alternatively or additionally, the focus corrector may apply different corrections to different beamlets within the same multi-beam. Thus, the focus corrector can provide focus correction at finer granularity levels to correct for, for example, manufacturing variations within the electron beam column 110 and/or smaller range variations in the height of the surface of the sample 208.

In some embodiments, the focus corrector comprises a mechanical actuator. The mechanical actuator applies each of one or more of the group focus corrections at least in part by mechanical actuation of the focus adjustment element. Mechanical actuation of the focus adjustment element may apply tilting and/or displacement of the entire electron beam column 110 or only a portion thereof (e.g., the objective lens array 118). For example, the focus adjustment element may comprise one or more electrodes of the objective lens array 118, and the mechanical actuator may adjust focus by moving one or more (e.g., all) of the electrodes of the objective lens array 118 (e.g., toward or away from the surface of the sample 208). The electrodes may be formed as one or more electrode plates integrated into the objective lens assembly. The electrode plates may be used (e.g., mechanically tuned) to control the focusing of the different beamlets in different ways.

In some embodiments, one or more scanning deflectors (shown in fig. 9) may be integrated with or directly adjacent to one or more of the objectives for scanning the beamlet waves 211, 212, 214 over the sample 208. In one embodiment, a scanning deflector may be used in accordance with the description in EP2425444A1 (the entire contents of which are incorporated herein by reference, and in particular the disclosure of using an aperture array as a scanning deflector).

The aberration corrector 126 may be a CMOS-based individually programmable deflector as disclosed in EP2702595A1, or a multipole deflector array as disclosed in EP2715768A2, the description of the sub-beam manipulator in both of which documents is incorporated herein by reference.

In one embodiment, the aberration corrector 126 comprises a field curvature corrector configured to reduce the field curvature. In one embodiment, the field curvature corrector is integrated with or directly adjacent to one or more of the objective lenses. In one embodiment, the field curvature corrector comprises a passive corrector. For example, a passive corrector may be implemented by varying the diameter and/or ellipticity of the aperture of the objective lens. For example, a passive corrector may be implemented according to the description in EP2575143A1, which is specifically incorporated herein by reference to correct astigmatism using an aperture pattern. The passive nature of the passive corrector is desirable because it means that no control voltage is required. In embodiments in which the passive corrector is implemented by varying the diameter and/or ellipticity of the aperture of the objective lens, the passive corrector provides other desirable features that do not require any additional elements, such as additional lens elements. The challenges of passive correctors are: they are fixed and therefore require careful calculation of the required correction in advance. Additionally or alternatively, in one embodiment, the field curvature corrector comprises an active corrector. The active corrector may correct the path of the charged particles in a controlled manner to provide correction. The active corrector may have electrodes for lines of charged particle beam paths across the beam array, wherein the electrodes operate on all sub-beams in the lines; an electrode associated with each beam path; or each beam path may have an electrode array surrounding the beam path. The electrodes may be individually addressable and may be controlled by means of CMOS circuitry. By controlling the potential of each of the one or more electrodes of the active corrector, the correction applied by each active corrector may be controlled. In one embodiment, the passive corrector applies a coarse correction, while the active corrector applies a finer correction and/or an adjustable correction.

Fig. 6 and 7 depict another embodiment of the objective lens array 118 and the detector 170. Such a configuration of objective lens array 118 and detector 170 may be used in conjunction with any of the multi-beam columns 110 and/or multi-beam column arrays discussed herein. In the arrangement shown, the objective lens array 118 includes a first electrode 121 and a second electrode 122. The second electrode 122 is located between the first electrode 121 and the sample 208. The first electrode 121 and the second electrode 122 may each include a conductive body having a plurality of lens apertures defining a corresponding plurality of objective lenses 118. Each objective lens 118 may be defined by a pair of apertures Ji Toujing, wherein one of the lens apertures is formed by the first electrode 121 and one of the lens apertures is formed by the second electrode 122. The lens aperture may be either circular or non-circular, e.g., elliptical. An aperture of this shape may be used to correct aberrations in the sub-beam off-axis as described in EP application number 21166214.3 incorporated herein by reference for modifications to the lens aperture used to correct off-axis aberrations.

Each objective lens may be configured to demagnify the beamlets by a factor of more than 10, ideally in the range of 50 to 100 or more. The power supply 160 applies a first potential to the first electrode 121. The power supply 160 applies a second potential to the second electrode 122. In one embodiment, the first and second potentials cause beamlets that pass through the objective lens array 118 to be decelerated to become incident on the sample 208 with desired landing energy. The second potential may be similar to the potential of the sample, e.g., about 50V or more. Alternatively, the second potential may be in the range of about +500V to about +1500V. The first potential and/or the second potential of each aperture may be varied to achieve focus correction.

In order to provide a deceleration function to the objective lens array 118 so that landing energy can be determined, it may be desirable to change the potential of the second electrode and the sample 208. In order to slow down the electrons, the second electrode is made to have a more negative potential with respect to the first electrode. The electrostatic field intensity is highest when the lowest landing energy is selected. The distance between the second electrode and the first electrode, the lowest landing energy between the second electrode and the first electrode, and the maximum potential difference are selected such that the resulting field strength is acceptable. The higher the landing energy, the lower the electrostatic field (less deceleration over the same length).

Because the electron optics configuration between electron source 199 and objective lens array 118 remains the same, the beam current remains unchanged with the change in landing energy. Changing landing energy may affect resolution, either by increasing resolution or decreasing resolution.

In some embodiments, as illustrated in fig. 6 and 7, the electron beam column 110 further includes a beam downstream aperture array 123. In the beam downstream aperture array 123, a plurality of apertures 124 are defined downstream of the beam of the objective lens array 118. Accordingly, beam downstream aperture array 123 may be located downstream of the beam of objective lens array 118. Each aperture 124 of apertures 124 is aligned with a corresponding objective lens 118. Thus, each of the apertures 124 of the beam downstream aperture array 123 has a corresponding objective in the objective array 118. Alignment is such that a portion of the electron beamlets from the objective lens 118 may pass through the aperture 124 and impinge on the sample 208. Still further, each aperture 124 is configured to allow only a selected portion (e.g., a central portion) of the electron beamlets incident on the beam downstream aperture array 123 from the objective lens to pass through the aperture 124. The cross-sectional area of aperture 124 may be smaller than, for example, the cross-sectional area of a corresponding aperture in beamlet-defining aperture array 152 or a corresponding beamlet incident on objective lens array 118. Accordingly, the aperture of the beam downstream aperture array may have a size (i.e., area and/or diameter and/or other characteristic dimensions) that is smaller than the corresponding aperture defined in the beamlet defining aperture array 152 and/or the objective lens array 118.

As illustrated in fig. 6 and 7, it may be desirable to provide a beam downstream aperture array 123 upstream of the beam of detector 170. Providing the beam downstream aperture array 123 upstream of the beam of the detector 170 ensures that the beam downstream aperture array 123 does not block charged particles emitted from the sample 208 and does not block them from reaching the detector 170.

Accordingly, the beam downstream aperture array 123 may be used to ensure that each electron beamlet exiting the objective lens in the objective lens array 118 has passed through the center of the respective lens. This can be achieved without requiring a complex alignment process to ensure good alignment of the beamlets incident on the objective lens with the objective lens. Moreover, the effect of beam downstream aperture array 123 is not compromised by column alignment actions, source instabilities, or mechanical instabilities.

In an electron beam column 110 having a collimator array 150 located downstream of the beamlets defining an aperture array 152 (e.g., as discussed above, for example, with reference to fig. 3) and/or in an electron beam column 110 without such a collimator array 150 (e.g., as discussed above, for example, with reference to fig. 4), an arrangement may be used that includes a beam downstream aperture array 123 configured to operate as described above with reference to fig. 6 and 7.

In the particular example of fig. 6 and 7, the beam downstream aperture body 123 is shown as an element formed separately from the bottom electrode of the objective lens array 118. In other embodiments, the beam downstream aperture body 123 may be integrally formed with the bottom electrode of the objective lens array 118 (e.g., by performing photolithography to etch away cavities on opposite sides of the lens aperture and beam blocking aperture that are suitable for use as lens apertures).

In one embodiment, the aperture 124 in the beam downstream aperture array 123 is provided at a distance from the beam downstream of at least a portion of the corresponding lens aperture in the bottom electrode of the corresponding objective lens array 118 that is equal to or greater than the diameter of the lens aperture, preferably at least 1.5 times greater than the diameter of the lens aperture, and preferably at least 2 times greater than the diameter of the lens aperture.

In the examples of fig. 6 and 7, beam downstream aperture array 123 is ideally positioned adjacent bottom electrode 122. Where the objective lens array 118 includes more than two electrodes (such as in an Einzel lens configuration), it may be desirable to locate the beam downstream aperture array 123 adjacent to the intermediate electrode. The intermediate electrode has a potential different from the beamlet energy, while the outer electrode has the same potential as the beamlet energy. In general, it may also be desirable to locate the beam downstream aperture array 123 in a region where the electric field is small, preferably in a region where there is substantially no field. This avoids or minimizes disruption of the desired lensing effect due to the presence of the beam downstream aperture array 123.

Fig. 8-10 provide further details regarding how to configure the detector for detecting charged particles emitted by the sample 208, with particular reference to an example scenario in which the charged particles are electrons. Any of the arrangements discussed below may be used to implement the objective lens array 118 and/or the detector 170 in any of the embodiments of the electron beam column 110 and/or the multi-beam column array discussed herein. For example, detector 170 may be configured in the same manner as detector modules 402 and/or 502, as mentioned below.

As illustrated in fig. 8-10, the objective lens may comprise a multi-electrode lens, wherein the bottom electrode is integrated with the CMOS chip detector array. The multi-electrode lens may include three electrodes, two electrodes, or a different number of electrodes as illustrated in fig. 8. The arrangement may be described as four or more lens electrodes as plates. Apertures are defined in the plate, for example as an array of apertures, which are aligned with several beams in the corresponding beam array. The electrodes may be grouped into two or more electrodes, for example, to provide a control electrode set and a target electrode set. In one configuration, the target electrode set has at least three electrodes (shown in fig. 8), while the control electrode set has at least two electrodes (not shown in fig. 8). There may be electrodes belonging to two groups, in which case one surface promotes one group of electrodes and the opposite surface promotes the other group of electrodes.

Integrating the detector array into the objective lens eliminates the need for a secondary column for detecting signal electrons. The CMOS chip is preferably oriented to face the sample (because the distance between the wafer and the bottom of the electron optical system is small (e.g., 100 μm)). In one embodiment, a capture electrode is provided for capturing signal electrons. The capture electrode may be formed in a metal layer of, for example, a CMOS device. The trapping electrode may form a bottom layer of the objective lens. The capture electrode may form a bottom surface in a CMOS chip. The CMOS chip may be a CMOS chip detector. The CMOS chip may be integrated into the sample facing surface of the objective lens assembly. The capture electrode is an example of a sensor unit or detector for detecting signal electrons. The trapping electrode may be formed in other layers. The power and control signals of the CMOS may be connected to the CMOS through silicon vias. For robustness, the bottom electrode is preferably composed of two elements: CMOS chips and passive Si plates with holes. The plate shields the CMOS from high electric fields.

The sensor unit (detector) associated with the bottom surface of the objective lens (objective lens array) or the surface facing the sample is advantageous because the signal electrons can be detected before the electrons meet and are manipulated by the electron-optical elements of the electron-optical system. Advantageously, the time taken for detecting such an electron-emitting sample may be reduced, preferably minimized.

An exemplary embodiment is shown in fig. 8, which fig. 8 illustrates a schematic cross section of an objective lens 401 (which may be referred to as an objective lens array). On the output side of the objective lens 401 (i.e. the side facing the sample 208), a detector module 402 is provided. Fig. 9 is a bottom view of a detector module 402, the detector module 402 comprising a substrate 404, the substrate 404 having a plurality of capture electrodes 405 disposed thereon, each capture electrode 405 surrounding a beam aperture 406. The beam aperture 406 is large enough so as not to block any of the primary electron beamlets. The capture electrode 405 may be considered as an example of a sensor unit or detector that is a detection signal electrode and generates a detection signal (in this case, a current). The beam aperture 406 may be formed by etching through the substrate 404. In the arrangement shown in fig. 9, the beam apertures 406 are shown in a rectangular array. The beam apertures 406 may also be arranged in different ways (e.g., hexagonal close-packed arrays).

Fig. 10 depicts a portion of a detector module 402 in cross-section on a larger scale. The capture electrode 405 forms the bottommost part of the detector module 402, i.e. the surface closest to the sample. A logic layer 407 is provided between the trapping electrode 405 and the body of the silicon substrate 404. The logic layer 407 may include amplifiers, such as transimpedance amplifiers, analog-to-digital converters, and readout logic. In one embodiment, each capture electrode 405 has an amplifier and an analog-to-digital converter. The logic layer 407 and the capture electrode 405 may be fabricated using a CMOS process, wherein the capture electrode 405 forms the final metallization layer.

Wiring layer 408 is provided on the backside of substrate 404 and is connected to logic layer 407 through silicon via 409. The number of silicon vias 409 need not be the same as the number of beam apertures 406. In particular, if the electrode signal is digitized in the logic layer 407, only a few silicon vias may be required to provide a data bus. Wiring layer 408 may include control lines, data lines, and power lines. It should be noted that despite the beam aperture 406, there is sufficient space for all necessary connections. The detection module 402 may also be fabricated using bipolar or other fabrication techniques. A printed circuit board and/or other semiconductor chips may be provided on the backside of the detector module 402.

Fig. 11 and 12 illustrate an alternative embodiment in which a detector (in this example, an electron detection device 240) for detecting charged particles emitted from the sample 208 is located in the beam downstream surface of the beamlet-defining aperture array 152.

In this example, the electron detection device 240 is positioned away from the electrode of the objective lens array that is furthest from the source (i.e., the beam downstream electrode that is remote from the objective lens array). In the example shown, the electronic detection device is integrated or associated with the upper electrode of the array of objective lenses 501. The substrate supporting the sensor unit 503 during operation may be held at the same potential difference as the upper electrode. In this position, the electrodes in the array of objective lenses 501 are closer to the sample than the electron detection device 240 or are downstream of the beam of the electron detection device 240. Thus, the signal electrons emitted by the sample 208 are accelerated to, for example, several kV (possibly about 28.5 kV). Thus, the sensor unit 503 may comprise, for example, a PIN detector or a scintillator. This has the following advantages: since the PIN detector and scintillator have a large initial amplification of the signal, there is no significant additional noise source. Another advantage of this arrangement is that the electronic detection device 240 is more easily accessible, for example, for power and signal connection or for maintenance when in use. It is also possible to use a sensor unit with a capture electrode at this location, but this may lead to poor performance. In the embodiment shown in fig. 12, the sensor units 503 are arranged in a hexagonal shape by way of example only. The sensor units 503 may be arranged in different ways, for example in a rectilinear grid.

The PIN detector comprises a reverse biased PIN diode and has an intrinsic (very lightly doped) semiconductor partition sandwiched between p-doped and n-doped partitions. The signal electrons incident on the intrinsic semiconductor region generate electron-hole pairs and allow a current to flow, thereby generating a detection signal.

The scintillator includes a material that emits light when electrons are incident thereon. The detection signal is generated by imaging the scintillator using a camera or other imaging device.

In an embodiment, the sensor unit 503 is configured to detect both secondary electrons and backscattered electrons, preferably with the detector of the sensor unit facing the sample in use. The secondary electrons can be distinguished from the back-scattered electrons. For example, in one embodiment, the sensor unit 503 may include separate partitions for detecting secondary electrons and backscattered electrons. These partitions may be separated from each other in a radial manner or in a circumferential manner.

The beam aperture 504 associated with the sensor unit has a smaller diameter than the aperture in the objective lens array to increase the surface of the sensor unit available for capturing electrons emitted from the sample. However, the beam aperture diameters are selected such that they permit beamlets to pass through; that is, the beam aperture 504 is not beam limiting. The beam aperture 504 is designed to permit beamlets to pass through without shaping their cross-section. The same principle applies to the beam aperture 406 associated with the sensor unit 402 of the embodiment described above with reference to fig. 11 and 12.

In another arrangement, the detector may be located on the objective lens. The detector may comprise sensor units arranged in an array, wherein each sensor unit is associated with a beamlet directed towards the sample. The sensor units may each take the form of a ring surrounding the path of the corresponding beamlet. In another arrangement, the detector may be upstream of the beams of the wien filter array to electronically transfer the signal (from the sample) to the corresponding detector element without affecting the path of the sub-beams directed towards the sample.

In one embodiment, the beam corrector array 145, the beam limiting aperture 133 (which may be present as an array), and/or the deflector array 134 and/or the objective lens array 118 are replaceable modules, either alone or in combination with other elements such as an array. The replaceable module may be field replaceable, i.e. the module may be exchanged for a new module by a field engineer. In one embodiment, a plurality of replaceable modules are contained within the tool and can be exchanged between an operable position and an inoperable position without having to turn on the electron beam device 40.

In one embodiment, the replaceable module is configured to be replaceable within the electron beam device 40. In one embodiment, the replaceable module is configured to be field replaceable. In-situ replaceable is intended to mean that the module can be removed and replaced with the same or a different module while maintaining the vacuum in which the electron beam device 40 is located. Only the section of the electron beam device 40 corresponding to the module is ventilated so that the module is removed and returned or replaced.

Fig. 13 is a schematic diagram of an electron beam apparatus 40 according to one embodiment of the invention. The electron beam device 40 is configured to project an electron beam (i.e., a beam of electrons 112) toward the sample 208. As shown in fig. 13, in one embodiment, the electron beam device 40 includes a plurality of electron optical columns 111. The electron optical column 111 is configured to project a respective electron beam towards the sample 208. In one embodiment, electron optical columns 111 are included in column array 200. It should be noted that in this arrangement, each electron optical column 111 projects a single beam towards the sample 208. As will be described, the beam passing through the column from the emitter of the source is shaped in a simple manner.

As shown in fig. 13, in one embodiment, each electron optical column 111 includes an electron source 199. Alternatively, the electron source 199 may be considered as a separate element from the electron optical column 111, wherein the electron source 199 provides electrons to the electron optical column 111. Electron source 199 is configured to emit a beam of electrons toward sample 208. As shown in fig. 13, electron source 199 is included in source array 131. In one embodiment, electron source 199 includes a tip from which electrons 112 are emitted. Alternatively, electron source 199 may have no tip. In one embodiment, electron source 199 comprises a semiconductor-based emitter 201. The source array 131 may include a substantially planar semiconductor substrate (see fig. 15). The semiconductor substrate may be common to the group of electron optical columns 111. In one embodiment, the semiconductor substrate of the source array is common to all electron optical columns 111.

In one embodiment, electron source 199 comprises an avalanche diode structure. The avalanche diode structure includes a stack of doped semiconductor junctions and is biased from two connections. For example, the avalanche diode structure may include a PN junction or a PIN junction. The avalanche diode structure may include a homojunction or heterojunction of a stack of semiconductors having different bandgaps. In one embodiment, the avalanche diode structure includes a heterojunction of a silicon carbide P-type substrate with a gallium nitride n++ layer on top. Gallium nitride has a lower work function (low-1 eV) so more electrons can escape from gallium nitride. At the same time, silicon carbide has a high thermal conductivity and the ability to make it P-type material. The bandgap structure affects the electron energy distribution in the avalanche region of the avalanche diode structure. The electron source 199 may be based on an Avalanche Electron Emission Diode (AEED) as an emitter technology. AEED emitters are semiconductor-based emitters. AEED may also be referred to as avalanche cold cathodes or semiconductor junction cold cathodes. In one embodiment, electron source 199 is junction-based. For example, the electron emitter 201 may include a diode junction, such as a PN junction. In one embodiment, the electron source 201 includes a plurality of junctions. Each junction may be an interface between two layers or segments of similar or dissimilar semiconductors. In one embodiment, the junction is the interface between the doped materials. The junction may be a junction between two or more materials. Such a junction may be a diode. In one embodiment, the electron source 201 is configured such that the avalanche current is generated inside a diode of the electron emitter 201, which diode is perpendicular to the surface facing the sample 208. Some electrons 112 are sufficiently excited in the avalanche region to overcome the work function of the surface and are emitted into vacuum.

Embodiments of the present invention are expected to more easily fabricate a larger number of electron sources 199 in the source array 131 on a substrate. In one embodiment, the electron beam device 40 comprises a greater number of electron emitters 201 than the sensor unit 503 of the detector 170. Such a source array of sources having multiple emitters per source has a high redundancy rate. In one embodiment, the electron emitter 201 is smaller. In one embodiment, the diameter of the electron emitter is at most 2 μm, optionally at most 1 μm, optionally at most 500nm, optionally at most 200nm, optionally at most 100nm, optionally at most 50nm, optionally at most 20nm and optionally at most 10nm. In one embodiment, the electron emitter has a diameter of at least 5nm, optionally at least 10nm, optionally at least 20nm, optionally at least 50nm, optionally at least 100nm, optionally at least 200nm, optionally at least 500nm and optionally at least 1 μm. Such emitters can be designed to be around 50nm in size and can be densely packed. The smaller the emitter, the smaller the size of the virtual source, and the reduced increase in brightness. Smaller small emitters may reduce interactions between electrons near the surface with the ejected electrons, thereby reducing energy spread between the emitted electrons. Small emitters may reduce local heat generation and/or increase local power dissipation. Because the surrounding lattice can reject heat better, the local power dissipation may be higher when the emitter is smaller.

In one embodiment, the electron emitter 201 comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride. These materials are semiconductors and have a suitably high band gap. These materials may have high doping levels. In particular, silicon carbide may be preferred because such materials also have high thermal conductivity and high electrical breakdown strength. This means that a high electric field can be applied inside the material to accelerate the electrons. In one embodiment, electron source 199 comprises a corresponding emitter 201, the corresponding emitter 201 comprising at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride. In one embodiment, silicon carbide, gallium nitride, aluminum nitride, or boron nitride forms the surface of the emitter. Electrons are emitted from the surface of the emitter. In one embodiment, a combination of two or more of silicon carbide, gallium nitride, aluminum nitride, and boron nitride are bonded together in the electron source 201. This material allows for higher avalanche current (compared to silicon) at higher breakdown voltages/electric fields.

These materials permit performance at high temperatures relative to silicon. In particular, because these materials have higher thermal conductivities, they are more effective than silicon in maintaining a locally low temperature. Embodiments of the present invention are expected to achieve an improved combination of brightness reduction of the emitter and energy spread of the emitted electrons. In general, when silicon is used for electron source 199, a tradeoff may be made between brightness reduction and energy spread.

By selecting the parameters of the electron emitter 201, the amount of energy required for electrons to escape can be controlled, which may be referred to as a work function. In general, an increased work function ideally narrows the energy distribution of electrons that can escape, and undesirably reduces the vacuum current density, thus reducing brightness. On the other hand, a reduced work function ideally increases the vacuum current density, thus increasing the reduced brightness, but undesirably widens the energy distribution of electrons that can escape.

Silicon carbide, gallium nitride, aluminum nitride, and boron nitride allow both high reduced brightness and narrow energy diffusion. In one embodiment, the material of the electron emitter 201 has a high thermal conductivity. Higher thermal conductivity may help provide higher local current density and higher reduced brightness. For example, silicon carbide has a high thermal conductivity. Embodiments of the present invention are expected to more easily keep electron source 199 cool. However, in an alternative embodiment, silicon is used instead of any of silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

As shown in fig. 13, in one embodiment, each electron optical column 111 is a single beam column. The electron optical column 111 is configured to: such that substantially all electrons 112 emitted by an electron source 199 associated with the electron optical column 111 that reach the sample 208 are included in a single beam. The electron beam emitted by electron source 199 reaches sample 208 without being split or generating additional electron beams. Each electron beam corresponds to an electron optical column 111. This simplifies the electron optics of each column, for example, because no off-axis beam is produced, thus requiring less collimation and aberration correction. The electron optical column 111 may be referred to as a micro-column. In an alternative embodiment, as described above and shown in fig. 2 and 3, the electron beam emitted by electron source 199 is split into multiple sub-beam waves that reach sample 208.

By having a single beam projected by each column, the beam can be along the electron optical axis of the column. This is in contrast to a multi-electron beam column in which all but the center beam is off-axis, resulting in all but the center beam having some off-axis aberrations. Such aberrations are typically corrected in electron optics, but such correction introduces additional complexity to the electron optics, such as where additional electron optics are required and/or existing electron optics are modified to reduce and/or eliminate the aberrations. Otherwise, uncorrected aberrations may reduce throughput.

In one embodiment, electron-optical column 111 is fabricated using MEMS technology. Embodiments of the present invention are expected to simplify MEMS-based electro-optical elements of the post 111. Embodiments of the present invention are expected to more easily produce MEMS-based electron optical columns 111. For example, it may be difficult to create converging lenses and collimator deflectors, for example, with correction features and additional correction elements. By providing the electron optical column 111 as a single beam column associated with their own electron source 199, it is easier and faster to align the electron optical column 111, e.g., with respect to the source, its emitter, and its electron optical elements, relative to each other, and to improve uniformity across the electron optical column 111, e.g., by avoiding the need for additional complexity of having multiple beam path columns and their associated aberration corrections.

As shown in fig. 13, in one embodiment, electron optical column 111 includes detector 170. The detector 170 may be as described above with reference to fig. 3, 6 and 8-12. For simplicity, details of the detector 170 are not repeated below, except to note that the detector may be positioned in the following manner: under the objective lens array; an objective lens array; associated with an associated additional electron optical lensing electrode; and proximally upstream of the beam of the objective lens array; and/or upstream of the beam of the objective lens array in the column.

Fig. 15 is a schematic diagram showing a plurality of electron emitters 201 for a source 199 of a single electron optical column 111 having a beam limiting aperture 133. Note that source 199 may include an extractor 132 that is not depicted. The electron optical column 111 may be of the type shown in fig. 13 or 14, for example. Any one of the plurality of electron emitters 201 shown in fig. 15 may emit an electron beam for the electron optical column 111, for example, to be used for an emitter group of the electron optical column 111. In one embodiment, at least three, optionally at least nine, optionally at least sixteen, and optionally at least one hundred electron emitters 201 are provided for electron-optical column 111. Accordingly, the substrate including the electron emitter 201 may include a plurality of emitter groups. Each set of emitters is for a different column. In one arrangement, a single emitter in the emitter array or emitter 201 is operated to emit an electron beam. For a group of emitters, there may be one extractor; or the extractor may be associated with a group of emitters such that the emitters of the group may be selected to provide an emitted electron beam. In another arrangement, a plurality of emitters may be selected from a group of emitters to operate to provide the emitted beam. As shown in fig. 15, all of the electron emitters 201 are near or near the axis of the electron optical column 111. In fig. 15, the axis is shown as a dot chain line. The axis corresponds to a line passing through the center of the aperture of the electron optical column 111 through which the electron beam passes.

For example, fig. 15 shows a beam limiting aperture 133 having an aperture through which an electron beam passes. The aperture of the beam limiting array is configured to define a cross-section of the electron beam directed onto the sample 208. In one embodiment, the beam limiting aperture 133 is configured to select a cross-section of the electron beam to be projected toward the sample 208. The beam limiting aperture 133 may be defined in a plate common to the plurality of electron optical columns 111. In one embodiment, the beam limiting aperture 133 may be defined in a plate common to all electron optical columns 111.

As shown in fig. 15, in one embodiment, the distance from the axis to each of the plurality of electron emitters 201 is less than the radius of the electron beam defined by the beam limiting array 133. In one embodiment, the distance from the axis to each electron emitter 201 of electron optical column 111 is less than 0.1, optionally less than 0.01, and optionally less than 0.001 of the radius of beam aperture 504. In one embodiment, each electron beam is effectively on-axis. In one embodiment, where the emitter size is 50nm, a large number of electron beams may lie within a range of 500nm beam axes, e.g., around a thousand emitters; however, a more practical controllable arrangement may have ten emitters, fifty emitters or around a hundred emitters. Such an arrangement of the emitter array may enable selection of emitter operation and indicates that any off-axis aberrations in the emitted electron beam are minimal. The electron optical column 111 is a single beam column embodiment of the invention is expected to reduce, if not prevent, the contribution to off-axis aberrations of the electron beam. Embodiments of the present invention are expected to reduce positional errors of beam spots formed on the sample 208 by the electron beam.

The beam limiting aperture 133 is configured to prevent some of the electrons 112 from reaching the sample 208. The blocked electrons 112 are electrons 112 that are farther from the axis of the electron optical column 111. In one embodiment, the beam limiting aperture 133 is configured to block at least 50% of electrons 112 that are directed to the beam limiting aperture 133. In one embodiment, the beam limiting aperture 133 is configured to block at least 80%, optionally at least 90% and optionally at least 95% of the electrons 112. The beam limiting aperture 133 is arranged such that at most 50%, alternatively at most 20%, alternatively at most 10% and alternatively at most 5% of the electron beam passes downstream of the beam limiting aperture 133. The proportion of the electron beam downstream of the beam passing through the beam limiting aperture 133 may be controlled, for example, by selecting the diameter of the aperture of the beam limiting aperture 133.

Embodiments of the present invention are expected to achieve a narrower energy spread of electrons 112 reaching the sample 208. As different electrons reach the sample 208, they may have different amounts of energy. A narrower energy range may be desirable. The electrons have an energy level that is at least the energy level that is required to escape from the electron emitter 201 to vacuum energy. This amount of energy may be referred to as escape energy. The escape energy of electrons depends in part on the radial position, i.e. the distance from the centre of the electron beam. The beam limiting aperture 133 is configured such that the substantially centrally located electrons are selected for guiding to the sample 208. By using only the center of the electron beam, the energy spread between electrons 112 is reduced. Generally, the electron energy tends to have a small varying common value in the central portion of the electron beam. Reducing the size of the central portion may also reduce variation.

In one embodiment, the pillar array 200 is formed as a stack of semiconductor layers. Embodiments of the present invention are expected to more easily scale up the number of electron beams projected onto the sample 208. In one embodiment, source array 131 is sized such that electron sources 199 are each assigned a column. Within the source array, the electron emitter 201 extends across a substantial portion of the sample 208. In one embodiment, source array 131 is sized such that electron source 199 extends across substantially all of the sample. Thus, the emitter 201 extends across substantially all of the sample. In one embodiment, source array 131 is at least as large as sample 208 under inspection when viewed along the optical axis. Various different sized samples 208 may be inspected. In one embodiment, the diameter of the sample 208 is 300mm, or alternatively 450mm. In one embodiment, source array 131 has a diameter of at least 300mm or at least 450mm. In an alternative embodiment, source array 131 is smaller than sample 208. For example, the source array 131 may be sized such that the electron emitter 201 extends across at least 10%, alternatively at least 20% and alternatively at least 50% of the diameter of the sample 208 (or sample holder 207). In one embodiment, the electron emitter 201 extends perpendicularly to the axis across at least about 30mm. In one embodiment, electron source 199 extends perpendicularly to the axis across at most about 50mm.

Embodiments of the present invention are expected to make it easier to provide an electron beam that is scaled to the size of the entire sample 208 or any other arbitrary size and/or shape. In one embodiment, electron sources 199 are arranged in a pattern that matches the shape of sample 208. For example, the pattern may be substantially circular. The pitch and/or distance between sources 199 corresponds to the pitch and/or distance between columns 111. Such pitch is in the range of 20 microns to 500 microns, more preferably 30 microns to 300 microns, or even 50 microns to 200 microns.

In one embodiment, source array 131 comprises a unitary substrate having electron emitters 201 formed thereon. In an alternative embodiment, source array 131 includes a plurality of substrates positioned adjacent to one another. For example, in one embodiment, a plurality of substrates having a dimension of about 100mm in a direction perpendicular to the optical axis are placed next to each other over a sample 208 having a dimension greater than 100 mm. Embodiments of the present invention are expected to make it easier to inspect a larger proportion of the surface of the sample 208 simultaneously. Embodiments of the present invention are expected to increase throughput, i.e., reduce the amount of time required to inspect the sample 208 (i.e., the sample surface).

As shown in fig. 13, in one embodiment, electron optical column 111 includes an objective lens. The objective lens may comprise at least one electrostatic electrode. In one embodiment, the objective lens comprises at least two electrodes, e.g. as described above with reference to fig. 6. The objective lens may be an electrostatic objective lens. An embodiment of the objective lens comprises three electrodes. The objective lens is configured to direct the electron beam toward the sample 208. The objective lens is included in the objective lens array 118. In one embodiment, one or more electrostatic electrodes of the objective lens are common to a plurality of electron optical columns 111. In one embodiment, one or more electrostatic electrodes are common to all electron optical columns 111.

The detector 170 is configured to detect signal electrons emitted from the sample 208. In one embodiment, the detector 170 is associated with the objective lens array 118. The detector 170 may be adjacent to the objective lens array 118 in the beam path of the electrons 112. The detector 170 may be located directly downstream of the beam of the objective lens array 118. In various embodiments, the detector may be located upstream of the beam of the objective lens array 118. In one embodiment, the detector 170 is directly associated with the objective lens array 118. The detector 170 and the objective lens array 118 may be included together in a module. In one embodiment, the detector 170 and the objective lens array 118 are integrated with each other.

As shown in fig. 13, in one embodiment, source array 131 includes a plurality of electron sources 199, which plurality of electron sources 199 are configured to emit respective electron beams. The column array 200 comprises a plurality of electron optical columns 111, the plurality of electron optical columns 111 being configured to project corresponding respective electron beams emitted by electron sources 199 of the source array 131 towards the sample 208.

As shown in fig. 13, in one embodiment, the objective lens is the beam downstream-most element of the electron optical column 111 that is configured to affect the electron beam directed toward the sample 208. The objective lens is in proximity to the sample 208. The detector 170 associated with the objective lens array 118 may be located further downstream in the beam than the objective lens. The detector 170 detects signal electrons emitted from the sample 208. The detector 170 is configured such that the electron beam directed toward the sample 208 passes through the location of the detector 170 without being affected by the detector 170. An objective lens having an electrode in common with the electron optical column 111 approaches the sample 208 along the path of the electron beam. Embodiments of the present invention are expected to reduce the distance between the objective lens and the sample 208. Bringing the detector close to the sample helps to reduce crosstalk between signal electrons generated by the beam of the column and the detectors of other columns.

In one embodiment, electron source 199 is configured to generate electron beams that are substantially identical to each other. There may be some variation between electron beams generated by different electron sources 201. In one embodiment, source array 131 includes a corrector configured to reduce variations between electron beams. The corrector may be CMOS based. In one embodiment, the electron optics of electron optical column 111 are configured to compensate for variations between different electron beams.

Embodiments of the present invention are expected to reduce the distance between electron source 199 and sample 207. For example, because there is no need to split the electron beam (or generate a sub-beam or sub-beam wave therefrom), less space is required to assemble the electron optics between the electron source 199 and the sample 208. The electron source 199 may be placed very close to the sample 208, i.e., if the column projects multiple beams and the column generates multiple sub-beams from the beams incident from the corresponding sources, the electron source 199 may be closer to the sample 208 than otherwise. In one embodiment, electron source 199 is configured to generate a lower current of electrons 112 than an electron source that generates an electron beam that is split before reaching sample 208. Embodiments of the present invention are expected to reduce coulomb interactions within an electron beam. Embodiments of the present invention are expected to reduce the voltage to which electrons 112 need to be accelerated. For example, in one embodiment, electrons 112 are accelerated to several kV, such as up to about 30kV, alternatively up to about 10kV, and alternatively up to about 5kV. However, in an alternative embodiment, electrons 112 are accelerated to less than 1kV, for example, at least about 200V, and optionally at least about 500V. In one embodiment, the landing energy of electrons 112 may be between 100eV and 10keV, preferably between 300eV and 3 keV. Embodiments of the present invention are expected to increase design freedom without unduly increasing the risk of electrical breakdown.

As shown in fig. 13, in one embodiment, electron optical column 111 includes an extractor 132, which extractor 132 may be referred to as an anode. Extractor 132 is configured to increase the amount of emission from electron source 199. In one embodiment, extractor 132 is located between electron emitter 201 and sample 208. Alternatively, the extractor 132 may be included in the electron source 201. In one embodiment, extractor 132 includes an electrode that is oppositely charged to charged particles (e.g., electrons). In one embodiment, the electrodes of the extractor 132 are common to the group of electron optical columns 111. In one embodiment, the electrodes of the extractor 132 are common to all electron optical columns 111. In one embodiment, the electrodes of the extractor 132 may be controlled simultaneously for multiple or all electron optical columns 111.

As shown in fig. 13, in one embodiment, electron optical column 111 includes a deflector. In one embodiment, the deflector is configured to deflect the electron beam in a direction perpendicular to the axis of the electron optical column 111. The deflectors may be included in a deflector array 134 for at least one group of deflectors of the electron optical column 111. In one embodiment, the deflector is included in a deflector array 134 for the deflectors of all electron optical columns 111. The deflectors of the deflector array 134 may be controlled to collimate the beams of the different columns of the multi-column array such that the deflector array 134 may be referred to as a collimator array. For example, the collimator array may collimate the beam such that the beam paths are all substantially parallel toward the sample. The deflector array may be controlled to electrostatically scan the beam across a portion of the sample surface in one direction or two orthogonal directions.

Fig. 14 is a schematic diagram of an alternative column array 200 of electron optical columns 111. In one embodiment, the electron optical column 111 shown in fig. 14 includes all of the features described above with respect to the arrangement shown in fig. 13. These features are not described again in the following in order to make this description more concise. As shown in fig. 14, in one embodiment, the electron optical column 111 comprises a converging lens arrangement 141 featuring at least one converging lens. A converging lens arrangement 141 is located between the electron source 199 and the sample 208. In one embodiment, the converging lens arrangement 141 is located upstream of the beam of the objective lens array 118. In one embodiment, the converging lens arrangement 141 is located upstream of the beam of the deflector array 134. In one embodiment, the converging lens arrangement 141 is located upstream of the beam of the aperture plate 135. Aperture plate 135 may not be beam limiting. The focusing lens of the focusing lens arrangement 141 is configured to operate on the electron beam. The aperture in aperture plate 135 may be at or around the intermediate focus of each electron beam.

In one embodiment, the converging lens arrangement 141 includes a converging lens electrode. The converging lens electrode may be a plate electrode of an electrode lens. The converging electrode may be common to a plurality of electron optical columns 111. In one embodiment, the converging lens electrode is common to all electron optical columns 111. In one embodiment, the converging lens arrangement 141 includes a plurality of converging lens electrodes, such as a beam upstream converging electrode 142 and a beam downstream converging electrode 144. The one or more beam upstream converging electrodes 142 may define a beam upstream converging lens; the one or more beam downstream converging electrodes may define a beam downstream converging lens. Beam upstream converging electrode 142 and beam downstream converging electrode 144 may be configured to modify the beam current of each electron source. The converging lens arrangement 141 may comprise a converging aperture 143, which may be a beam limiting aperture. The condenser aperture 143 may shape the beam, especially in an arrangement where there is no further beam limiting aperture. The collector aperture 143 is located between the beam upstream and downstream collector lenses. In one embodiment, the collector apertures 143 are included in a collector aperture array for at least one group of electron optical columns 111; each aperture of the array operates on a beam of a different column. In one embodiment, the collector aperture 143 is included in an array of collector apertures for all electron optical columns 111. In one embodiment, the beam upstream converging electrode 142 is common to at least one group of electron optical columns 111. In one embodiment, the beam upstream converging electrode 142 is common to all electron optical columns 111. In one embodiment, the beam downstream converging electrode 144 is common to at least one group of electron optical columns 111. In one embodiment, the beam downstream converging electrode 144 is common to all electron optical columns 111. In an alternative embodiment, a different device is used for the converging lens arrangement 141.

As shown in fig. 14, in one embodiment, the converging lens arrangement 141 is configured to focus the electron beam at an intermediate focus 146. The intermediate focus 146 is located between the converging lens 141 and the sample 208. In one embodiment, the intermediate focus 146 of the plurality of electron optical columns 111 is disposed within a common intermediate focus plane 147. The intermediate focal plane may be common to all electron optical columns 111. In one embodiment, intermediate focus 146 is located between aperture plate 135 and deflector array 134, ideally if the modules are not optimally mechanically aligned, for example to account for alignment of the column modules upstream and downstream of intermediate focus 146 in, for example, a straightened beam path. The electron beam may diverge between the intermediate focus 146 and the objective lens array 118. The electron beam need not have an intermediate focus 146. In an alternative embodiment, the converging lens 141 is configured to collimate the electron beam directed to the objective lens array 118.

As shown in fig. 14, in one embodiment, electron optical column 111 includes individual beam compensators. The individual beam corrector is configured to correct characteristics of the electron beam. In one embodiment, individual beam compensators are included in the beam corrector array 145 for at least one group of electron optical columns 111. The beam corrector array 145 may be configured to provide individual beam corrections to the electron beam. The individual electron beam corrections may be corrections to the alignment of the electron beam and/or optimizations to the current of the electron beam. For example, the beam corrector of the beam corrector array 145 may improve or even correct the alignment of individual electron beams such that the paths of the electron beams pass through the corresponding apertures of the aperture plate 135. In one embodiment, individual beam compensators are included in the beam corrector array 145 for all electron optical columns 111. In one embodiment, the individual beam corrector is configured to provide, for example, correction for any astigmatism and/or associated beam alignment.

Thus, the function of the aperture plate 135 may be defined, wherein an intermediate focus should be formed. The positioning of the aperture plate 135 may facilitate alignment of the upper portion of the respective electron optical column 111 and the bottom portion of the respective electron optical column 111 relative to each other. The alignment function may be desirable if the electron optical column consists of two modules (e.g., a bottom portion and an upper portion) (ideally the aperture plate 135 acts as the electron optical element of the bottom module that is the most upstream of the beam); or if the electron-optical column is a single module, wherein the electron-optical elements of the bottom part are secured together in a stack, thus limiting misalignment inside the bottom part, this alignment function may be desirable. For example, the electro-optical elements of the bottom portion are attached together using an adhesive such as glue.

As shown in fig. 14, in one embodiment, the individual beam corrector is located directly downstream of the beam of the converging lens arrangement 141 and, in one arrangement, is integrated into the converging lens arrangement 141. As shown in fig. 14, in one embodiment, individual beam compensators are located upstream of the beam of aperture plate 135. In an alternative embodiment, the individual beam compensators are located directly downstream of the beams of the deflector array 134. In an alternative arrangement, for example, individual beam compensators are integrated into the deflector array 134 such that the deflector array 134 has the functionality of the individual beam compensators and deflector array 134. These positions are chosen because: once the aberrations are generated in the converging lens arrangement or near the intermediate focus if not at the intermediate focus, the aberrations are advantageously corrected, where the correction is least likely to cause other aberrations.

As shown in fig. 14, in one embodiment, each electron optical column 111 includes a plurality of individual beam compensators. Individual beam correctors may be grouped together in a beam path. Individual beam correctors may be used to correct different characteristics of the electron beam. In one embodiment, the individual beam corrector comprises a multipole deflector. The multipole deflector may be manufactured using MEMS technology. In one embodiment, the fabrication process is bipolar compatible or uses CMOS technology, allowing incorporation of local electronics, e.g., implementing sample and hold functions. The multipole may be a quadrupole having four poles. Alternatively, the multipoles may include, for example, eight or twelve poles or any reasonable number (e.g., multiples of four) of poles. In one embodiment, the multipole deflector comprises a substantially planar substrate provided with an array of through openings arranged in rows and columns in a regular manner. The through opening extends substantially transversely to the surface of the planar substrate and is arranged for passing at least one electron beam therethrough.

In one embodiment, the multipoles are associated with corresponding voltage dividers. The voltage divider is configured to distribute a voltage to the multipole electrodes. In one embodiment, the electronic control circuit is associated with a multipole deflector. The electronic control circuit may comprise an integrated circuit that has been arranged adjacent to the through opening (in particular on the non-beam region of the planar substrate). On top of the electronic control circuit an insulating layer may be provided, on top of which an electrode layer may be arranged. The electronic control circuitry is configured to control the electrodes of the multipole deflector, for example, to provide a uniform electric field across the aperture of the multipole around the beam path to operate on the corresponding beam.

Although not shown in fig. 13 or 14, in one embodiment, each electron optical column 111 includes a control lens array. The steering lens array is located upstream of the beam of the objective lens array 118. The control lens array is associated with the objective lens array 118. The control lens array is configured to control at least one parameter of the electron beam. For example, the control lens array may be configured to control landing energy of the electron beam. In one embodiment, the control lens array includes a plurality of control lenses. Each control lens includes at least two electrodes (e.g., two or three electrodes) that are connected to respective potential sources.

In one embodiment, each electron optical column 111 includes a plurality of electron emitters 201. In such an arrangement, the source 199 associated with a particular electron optical column is considered or even part of the structure of the electron optical column 111, which need not be the case. In one embodiment, the electron emitters 201 are configured to be selectable such that a subset of the electron emitters 201 of the electron source 199 may be selected to emit an electron beam toward the sample 208. By providing an electron emitter 201 that can be selected to provide an electron beam to the source 199 and its associated electron optical column 111, there is some redundancy in the electron emitter 201. Embodiments of the present invention are expected to increase the reliability of the electron optical column 111 having functionality. Due to yield errors, there may be insufficient performance of electron emitters 201 in source array 131. By providing redundancy, an underperforming transmitter is less likely to adversely affect the device.

There are different ways in which the electron emitter 201 can be selected. In one embodiment, the electron emitter 201 is configured such that the selected electron emitter 201 is operable (i.e., turned on) to be selected. In one embodiment, each electron emitter 201 is configured to be individually controllable to be turned on or off.

In one embodiment, the electron emitters may be selected by deflecting the electron beam from the selected emitter toward a beam path in the electron optical column 111. This selection may be achieved by an arrangement of deflectors (not shown) arranged to deflect the beam from source 199 along the electron optical axis of column 111. For example, for about 10 sources per column, the distance between the sources is small such that the deflection of the path of the beam is small enough that aberrations such as chromatic aberration are not significantly introduced. In one embodiment, the electron optics source 209 may include a deflector. The deflector may be an array, for example, an array of deflectors. The deflector may be associated with the transmitter. The deflector is configured to deflect electrons emitted by the emitter such that its path is in a direction along the axis of the electron optical column 111. The electron beam emitted by the selected emitter of the source in the source array may then be directed to the axis of the electron optical column.

As shown in fig. 5, in one embodiment, electron-optical columns 111 are arranged in a pattern in column array 200 when viewed along an optical axis. The pattern may be a grid. For example, as shown in fig. 5, the pattern may be a rectilinear grid. In another arrangement, the pattern may be hexagonal. The grid may be irregular such that it is skewed, shifted or offset. Alternatively, the pattern may be hexagonal such that alternating rows of electron-optical columns 111 are offset by half the pitch between adjacent electron-optical columns of the same row.

In one embodiment, the electron sources 199, or at least their electron beam paths, are arranged in a pattern in the source array 131 when viewed along the optical axis. The pattern may be a grid. For example, the pattern may be a rectilinear grid or a hexagonal grid, which may be irregular. Alternatively, such a hexagonal pattern may be regular, for example, such that alternating rows of electron sources 199 are offset by half the pitch between adjacent electron sources 199 of the same row. The electron sources may be arranged in a skewed hexagonal grid. Such a skewed or offset pattern may be desirable because it may help ensure that the path of each beam of the electron optical column has a path on the sample that partially overlaps the path of the other beam. However, all paths of the source array may be different. This arrangement may be beneficial because it achieves redundancy. If a source were to fail, the contribution of the failed source would be taken up by the other sources of source array 131.

In one embodiment, the pitch between electron emitters 201 corresponding to the same electron optical column 111 may be much smaller than the pitch between electron optical columns 111 (e.g., because the position of the group of sources is within a small proportion of the diameter of the derived beam). The electron emitters 201 corresponding to the same electron optical column 111 may be arranged in a hexagon around the beam path. Electron sources 199 may be arranged in a skewed hexagonal grid.

The pattern may include multiple groups of electron emitters 201, each group corresponding to one of the electron optical columns 111 and/or to a source 199. In one embodiment, the source 199 or set of electron emitters comprises at least 10, optionally at least 20, and optionally at least 50 electron emitters 201. In an embodiment, source 199 comprises at most one hundred fifty, optionally at most one hundred, or optionally at most fifty, and optionally at least twenty electron emitters 201. In one embodiment, the groups of emitters 201 are separated by a partition in which there are no electron emitters provided (i.e., a partition without emitters). In an alternative embodiment, electron emitters 201 are arranged at regular intervals of source array 131, such as emitters 201 or a specified number of emitters spaced in a regular manner on the surface of source array 131.

Fig. 16 is a schematic view of the optical axis of the arrangement of electron optical columns 111 along the column array 200. In one embodiment, the electron beam device 40 is configured such that the sample holder 207 and the electron optical column 111 are movable relative to each other in the scanning direction 161. The scanning direction 161 is perpendicular to the optical axis. During use of the electron beam device 40, the sample holder 207 can be moved by operating the motorized stage 209. Additionally or alternatively, the array of posts 200 may be mechanically moved in a direction perpendicular to the optical axis. The electron optical column 111 moves along a scan path relative to the sample 208. In one embodiment, the scan path includes a straight line segment. The scan path may include a series of straight sections joined via bends. The straight sections may be parallel to each other. The straight sections may be separated from each other by a distance such that during the scanning process, all surfaces of the sample 208 are within the field of view of the at least one electron optical column 111.

Fig. 16 schematically shows a pattern in which electron optical columns 111 such as shown in fig. 13 or 14 are arranged. As shown in fig. 16, the arrangement may be a rectilinear grid. Alternatively, a hexagonal grid arrangement may be used. Such a grid may be irregular, such as offset, shifted or skewed. In one embodiment, electron optical columns 111 are arranged in parallel lines. In fig. 16, three parallel lines are shown, each line including three electron optical columns 111. The number of electron optical columns 111 in each line may be at least 10, alternatively at least 100, and alternatively at least 1000. The number of parallel lines may be at least 10, alternatively at least 100, and alternatively at least 1000.

As shown in fig. 16, in one embodiment, the parallel lines are inclined at an angle α to the scan direction 161. Such an inclination angle in the grating may cause the grating to be irregular. By having parallel lines at an oblique angle α to the scanning direction 161, redundancy may be introduced in the scanning technique. The tilt angle α corresponds to an array of electron beams formed by the electron optical column 111, which electron optical column 111 has an aligned rotation about a vertical axis (i.e., an axis parallel to the direction of the electron beams). The grid in which the electron optical column 111 is arranged is skewed with respect to the scanning direction 161. In one embodiment, the angle of inclination α is at least 1 °, alternatively at least 2 °, alternatively at least 5 °, alternatively at least 10 °, and alternatively at least 20 °. In one embodiment, the inclination angle α is at most 20 °, alternatively at most 10 °, alternatively at most 5 °, alternatively at most 2 °, and alternatively at most 1 °. Thus, during scanning, the path of the sample under the array of posts aligns the paths of the beams on the surface of the sample with each other, so that a partition of the sample surface is scanned. That is, the path of the beam on the surface does not overlap with the path of another beam in the array of posts. The beam aperture 504 is arranged and aligned relative to the scan direction 161 such that overlap between beam paths in the scan is reduced or avoided. There may be some (but not complete) overlap between beam paths in the scan.

In one embodiment, the electron beam device 40 includes a controller 50, the controller 50 being configured to selectively control the electron optical column 111 to shape the respective electron beam through the respective beam limiting aperture 133 such that electrons of the respective electron beam that are less than a threshold current density pass through the respective beam limiting aperture 133. This is illustrated for example in fig. 13. The electron beam is shaped such that a proportion of the current electrons of the electron beam are prevented from passing through the beam limiting aperture 133. Preventing a proportion of the electrons of the electron beam from reaching the sample 208. The proportion of the electron beam passing through the beam limiting aperture 133 may be at most 50%, alternatively at most 35%, alternatively at most 20%, alternatively at most 10%, alternatively at most 5%, alternatively at most 2%, and alternatively at most 1%.

In one embodiment, the controller 50 is further configured to selectively control the electron optical column 111 such that at least a threshold current density of electrons in at least a proportion of the electron beams passes through the respective beam limiting aperture 133, 143. This is illustrated for example in fig. 17. In one embodiment, substantially all of the electron beam passes through the beam limiting aperture 133. Alternatively, a proportion of the electrons may be blocked from current electrons. However, sufficient current electrons pass through the beam limiting aperture 133 to flood. The flooding is as follows: when electron beam charges are deposited on the surface of the sample 208 prior to inspecting the sample 208. Flood irradiation may help increase contrast when inspecting the sample 208 for defects. For example, flood ejection may help to improve the resulting image contrast, e.g., by supplying additional charge to the sample 208. Thus, flooding helps to increase the range of contrast of the resulting image. The additional charge on the sample 208 increases the chance of interaction between the incident electrons of the primary beam and thus increases the chance of emitting signal particles for detection. Increasing the chance of generating signal particles results in an increased detection chance and a stronger detection signal. As the detection rate of signal particles increases, the signal may be stronger, thereby making the contrast in the image greater, increasing the ease with which certain types of information can be obtained from the image. A greater contrast may help determine defects. Additional information may be obtained from the resulting image compared to an image made at a lower contrast setting. At different contrast settings, different information can be derived from the image. Varying the contrast across the contrast range in this way enables a larger information range to be achieved than from an image at a particular contrast setting. Thus, the ability to increase the contrast of the image makes it easier to find certain types of defects. For voltage contrast based inspection, high density flood is required. The proportion of electrons of the electron beam passing through the beam limiting aperture 133 may be at least 2%, alternatively at least 5%, alternatively at least 10%, alternatively at least 20%, alternatively at least 50%, alternatively at least 80%, alternatively at least 90%, alternatively at least 95%, and alternatively substantially 100%.

The controller 50 is configured to control the electron optical column 111 so as to control the proportion of the electron beam passing through the beam limiting aperture 133. The controller 50 is configured to selectively control the electron optical column 111 to control the electron beam, as shown in fig. 13 and 17. In one embodiment, the controller 50 is configured to switch between the settings shown in fig. 13 and 17. In one embodiment, the controller 50 is configured to control the electron optical column 111 to operate in the mode shown in fig. 13 (e.g., a mode suitable for inspection or evaluation) or the mode shown in fig. 17 (e.g., a mode suitable for flooding).

Note that fig. 17 depicts an embodiment in which one or more common elements of different adjoining electron optical columns 111 are formed of the same element. For example, at least one electrode (not all electrodes of the objective lens) is common to at least one electrode of the objective lens array 118. The beam limiting aperture 133 may have, for example, an array in a plate common to two or more electron optical columns 111 (e.g., all electron optical columns 111). One or more other elements of electron optical column 111 may have common elements.

In one embodiment, the controller 50 is configured to control the electronic device 40 to perform flooding of the surface of the sample 208. The controller 50 controls the electronic device 40 to flood the surface of the sample 208 when at least a threshold current density of the at least a proportion of the beamlets passes through the respective beam limiting aperture 133. The electronic device 40 is configured to have a flood mode of operation. In one arrangement, the inspection beam current may be sufficient to flood at least a portion of the surface of the sample 208 by a semiconductor-based emitter (such as, for example, a silicon-based emitter as disclosed herein, such as AEED emitter). That is, the current density of the beamlets is at least a threshold current density. In one arrangement, the current density may meet or exceed a threshold current density, but for a desired flood of a portion of the sample surface during the flood mode, the dwell time during, for example, a relative scan between the beamlets and the surface may be greater than the dwell time during the inspection mode. In another arrangement, the beam current (or probe current) at the sample surface is increased for the flood mode to meet or exceed a desired threshold current density. Reasons including increasing beam current during flood mode may depend on various factors, such as the gauge of the probe spot. The following description contemplates arrangements when beam current needs to be increased to meet or exceed a threshold current density.

In one embodiment, the primary electron beam for flood irradiation is the same as the primary electron beam for inspection. Embodiments of the present invention are expected to realize flooding without an electron optical column for flooding separate from the electron optical column 111 for inspection. By using the same electron-optical column 111 for both flooding and inspection, less or no movement of the sample 208 relative to the electron-optical column 111 is required in order to perform an inspection of the surface of the sample 208 that has undergone flooding. In order to inspect the sample 208 with high contrast, less time is required to move the sample 208 relative to the electron optical column 111. Embodiments of the present invention are expected to increase throughput by reducing the time required to perform inspection using flood.

The current of electrons on the sample 208 is greater when at least a proportion of the electron beam of the threshold current density in the electron beam passes through the respective beam limiting aperture 133 than when the electron beam is shaped through the respective beam limiting aperture 133. This shaping of the electron beams by the respective beam limiting apertures 133 determines that electrons of each respective beam that are less than the threshold current density pass through the respective beam limiting aperture 133.

As shown in fig. 13 and 17, in one embodiment, each electron optical column 111 includes a detector 170. The detector 170 is configured to detect signal electrons emitted from the sample 208. In one embodiment, the controller 50 is configured to control the electron beam device 40. The controller 50 controls the operation of the electron beam device 40 to detect signal electrons emitted by the sample 208 as the respective electron beam is shaped through the beam limiting aperture 133. Such a shaped respective electron beam is shaped by the respective beam limiting aperture 133 such that electrons of the respective electron beam that are less than the threshold current density pass through the respective beam limiting aperture 133.

The threshold current density may be referred to as a flood threshold. In one embodiment, the threshold current density is at least three times the current of the electron beams as they are shaped through the respective beam limiting aperture 133, such that electrons of each electron beam that are less than the threshold current density pass through the respective beam limiting aperture 133. The flood current density is at least three times the examination current. Optionally, the flood current is at least 5 times, optionally at least 10 times, and optionally at least 20 times the inspection current. (note that the flood current is higher but the current density for examination may be higher, since it is over a much smaller area due to the very small detected spot; while the flood is over the whole region of interest, but the current density relative to the detected spot is still lower).

In one embodiment, flooding is performed simultaneously using a plurality of electron beams. This is in contrast to other systems that may use a single flood beam. By using multiple electron beams simultaneously, the speed required for relative movement between the sample 208 and the electron optical column 111 is reduced. Embodiments of the present invention are expected to reduce the design requirements for the motorized stage 209.

As shown in fig. 13 and 17, in one embodiment, each electron optical column 111 includes an extractor 132, the extractor 132 being common to the electron optical columns 111, preferably at least a proportion of the electron optical columns 111. The extractor 132 may be included in the source. The source may be part of a respective electron optical column 111. The extractor 132 is located between the emitter 201 and the beam limiting aperture 133. In one embodiment, the controller 50 is configured to control the voltage applied to the extractor 132 in order to control the opening angle of the respective electron beam from the emitter 201 towards the beam limiting aperture 133 in order to control the extent to which the respective electron beam is shaped through the respective beam limiting aperture 133. This can be seen from a comparison between fig. 13 and 17. Fig. 13 shows a wider opening angle such that a smaller proportion of the electron beam passes through the beam limiting aperture 133. Fig. 17 shows a narrower opening angle such that a larger proportion of the electron beam passes through the beam limiting aperture 133.

Fig. 21 shows a modified version of the electron beam device 40 shown in fig. 13 and 17. As shown in fig. 21, in one embodiment, each electron optical column 111 includes an open angle electrode 190, which open angle electrode 190 is common to the electron optical columns 111, preferably to at least a proportion of the electron optical columns 111. An open angle electrode 190 is located between the emitter 201 and the beam limiting aperture 133. An open angle electrode 190 is located between the extractor 132 and the beam limiting aperture 133. In one embodiment, the controller 50 is configured to control the voltages applied to the opening angle electrodes 190 in order to control the opening angles of the corresponding electron beams from the emitters 201 towards the beam limiting apertures 133 in order to control the extent to which the corresponding electron beams are shaped through the respective beam limiting apertures 133. The opening angle electrode 190 is not indispensable. The function of controlling the opening angle of the electron beam toward the beam limiting aperture 133 may be performed by the extractor 132.

In one embodiment, the controller 50 is configured to control the electron optical column 111 to reduce the cross-section of the electron beam at the beam limiting aperture 133. This can be seen from a comparison between fig. 13 and 17. In fig. 17, the controller 50 controls the electron-optical column 111 to focus the respective electron beams to reduce (relative to the situation shown in fig. 13) their cross-sections at the beam limiting aperture 133. This increases the proportion of the current of the electron beam passing through the beam limiting aperture 133.

As shown in fig. 17, all electron beams may be controlled to increase the proportion of their current reaching the sample 208 in order to perform flooding. In an alternative embodiment, a portion, but not all, of the electron beam is controlled to perform flooding.

The controller 50 that switches between the inspection mode (e.g., fig. 13) and the flooding mode (e.g., fig. 17) is applicable to embodiments different from those shown in fig. 13 and 17. For example, fig. 14 shows an electron beam device 40 that may be in an inspection mode. Fig. 18 shows the arrangement of fig. 14 operating in a different manner. Fig. 18 shows the electron beam device 40 shown in fig. 14 in flood mode. It should be noted that for the electron beam device of fig. 14, the flood mode is achieved at a maximum beam current, and for this design of the electron beam device, the setting of the maximum beam current can also be used for inspection. The flood mode is an adjusted inspection setting.

As shown in fig. 18, the controller 50 may be configured to control the electron-optical column 111 to focus the respective electron beams such that the flood current passes through the beam limiting aperture of the collector aperture 143 and the aperture of the aperture plate 135. As shown in fig. 18, substantially all of the electron beam projected downstream of the beam of the converging lens arrangement 141 passes through the aperture plate 135. In the situation shown in fig. 14, a smaller proportion of the electron beam passes through the beam limiting aperture 143. In one embodiment, the controller 50 is configured to control the voltage applied to the extractor 132 in order to control the proportion of the electron beam passing through the beam limiting aperture 143. Additionally or alternatively, an additional opening angle electrode (not shown in fig. 14 or 18) may be provided between the extractor 132 and the beam limiting aperture 143. The controller 50 may be configured to control the voltage applied to the opening angle electrode in order to control the proportion of the electron beam passing through the beam limiting aperture 143. Additionally or alternatively, the controller 50 may be configured to control the voltage applied to one or more electrodes of the converging lens arrangement 141 in order to control the proportion of the electron beam passing through the beam limiting aperture 143.

Note that fig. 18 depicts an embodiment in which one or more common elements of different adjoining electron optical columns 111 are formed of the same element. For example, at least one electrode (not all electrodes of the objective lens) is common to at least one electrode of the objective lens array 118. The aperture plate 135 may have, for example, an array in a plate common to two or more electron optical columns 111 (e.g., all electron optical columns 111). The beam limiting aperture 143 may have, for example, an array in a plate common to two or more electron optical columns 111 (e.g., all electron optical columns 111).

Fig. 19 is an end view of the beam downstream surface of the column array 200 of electron optical columns 111. A plurality of capture electrodes 405 each surrounds a beam aperture 406. The capture electrode 405 may be considered as an example of a sensor unit or detector 170, which sensor unit or detector 170 detects the signal electrode and generates a detection signal (in this case, a current). In the arrangement shown in fig. 19, the beam apertures 406 are shown in a hexagonal array. The beam apertures 406 may also be arranged in different ways (e.g., rectangular arrays).

As shown in fig. 19, in one embodiment, the electron beam device 40 includes a plurality of flood columns 192. The flood column 192 is configured to project a respective flood electron beam toward the sample 208. Each flood column 192 includes at least one electron emitter configured to emit a flood beam toward sample 208. In one embodiment, each flood column 192 includes a plurality of emitters. The electron emitters are included in a source array. The flood column 192 is arranged to project a larger electron current onto the sample 208 than the electron optical column 111.

In one embodiment, the flood column 192 is configured to project a flood current of electrons (i.e., at least a threshold current density) onto the sample 208. In one embodiment, the controller 50 is configured to control the flood column 192 to project the flood beam when flooding is to be performed. When an inspection is to be performed, the controller 50 may control the flood column 192 to cut off the flood beam.

As shown in fig. 19, in one embodiment, the flood column 192 has a smaller cross section than the electron optical column 11 used for inspection. By providing the flooding column 192, the control required to perform flooding can be simplified.

In one embodiment, the controller 50 is configured to control the motorized stage 209 to control movement between the sample 208 and the column array 200. This movement may be performed to switch between the flood column 192 and the electron optical column 111 above the target region of the sample 208 for inspection. The relative movement may correspond to a pitch from the flood column 192 to the electron optical column 111. As shown in fig. 19, in one embodiment, the flood columns 192 are interspersed between electron optical columns 111. Embodiments of the present invention are expected to reduce movement between flood mode and inspection mode.

As shown in fig. 19, in one embodiment, the flood columns 192 are positioned adjacent to the respective electron optical columns 111. In one embodiment, the pitch of the flood column 192 is similar to the pitch of the electron optical column 111. For example, the electron optical columns 111 may be arranged in a grid. The flooding columns 192 may be arranged in a pattern in which the flooding columns 192 are located between at least two adjacent electron optical columns 111 (preferably, substantially equidistant between at least two adjacent electron optical columns 111). In one embodiment, the flood column 192 may be positioned along a line between two adjacent electron optical columns 111.

Fig. 20 shows an end view of a different arrangement of post arrays 200 with flood posts 192. As shown in fig. 20, in one embodiment, the flood columns 192 are arranged in a pattern in which the flood columns 192 are located between at least three adjacent electron optical columns 111; the three adjacent electron optical columns 111 may be referred to as three nearest neighbor electron optical columns 111. Preferably, the flooding columns 192 are located substantially equidistantly between at least two adjacent electron optical columns 111 of the three adjacent electron optical columns 111, even between the three adjacent electron optical columns 111. The flood column 192 may be positioned along a line between two adjacent electron optical columns 111. Alternatively, the flood column 192 may be positioned away from the line between two adjacent electron optical columns 111. The distance between two adjacent flood columns 192 may be substantially the same as the distance between two adjacent electron optical columns 111. In one embodiment, the distance between any adjoining electron optical column 111 and flood column 192 may be substantially the same.

The description with reference to fig. 19 and 20 refers to the positioning of the flooding post 192 with respect to the adjoining electron optical post. Variations within the scope of the depicted arrangement and description associated with the figures may alternatively be described with reference to the positioning of electron optical column 111 relative to flood column 192.

In one embodiment, the flooding columns 192 are arranged in a grid similar to the grid of the electron optical columns 111, and the flooding columns 192 are offset relative to the grid of the electron optical columns 11 so as to follow the lines between two adjoining electron optical columns in the electron optical column grid, as shown in fig. 19. In one embodiment, the flood column 192 is arranged in a grid similar to the grid of the electron optical column 111. The flood column 192 is offset relative to the grid of electron optical columns 11 so as to have three adjacent electron optical columns 11 spaced apart by 1 over a similar displacement range, as shown in fig. 20.

In one embodiment, the electron beam device 40 includes an actuator (e.g., included in the motorized stage 209) configured to actuate the sample holder 207 relative to the electron optical column 11 in orthogonal actuation directions 190, 191. In one embodiment, the flood column 192 is positioned relative to the respective electron optical column 111 in at least one of the actuation directions 190, 191. By matching the position of the flood column 192 relative to the electron optical column 11 to the actuation direction, only one actuator may be required to move the sample 208 between the flood position and the inspection position.

For example, as shown in fig. 19, the flood column 192 may be positioned relative to the respective electron optical column 111 in an actuation direction 190, the actuation direction 190 being from left to right in the view of fig. 19. Additionally or alternatively, as shown in fig. 20, the flooding posts 192 may be positioned relative to the respective electron optical posts 111 in an actuation direction 191, the actuation direction 191 being from top to bottom in the view of fig. 20.

In one embodiment, the number of flood columns 192 is equal to or less than the number of electron optical columns 111. The ratio of the flood column 192 relative to the electron optical column 11 is optionally at least 0.5, optionally at least 0.8, optionally at least 0.9, optionally at least 0.95 and optionally 1. When fewer flood columns 192 than electron optical columns 111 are provided, each flood column 192 may be used for a plurality of electron optical columns 111. Each flood column 192 may be used to flood the surface of sample 208 corresponding to the location to be inspected by the plurality of electron optical columns 111. Additional movement of the sample 208 relative to the electron optical column 111 may have to be performed.

Fig. 22 is a schematic diagram of a column array 200 including electron optical columns 111 and flood columns 192. The column array 200 is arranged with alternating electron optical columns 111 for inspection and flood columns 192 for flood.

As shown in fig. 22, in one embodiment, each flood column 192 includes an extractor. The extractor is configured to increase the emission of electrons from the emitter 201. The extractor is located downstream of the beam of the emitter 201. Extractor 132 and emitter 201 may together comprise at least a portion of an electron source 199. The extractor is common to at least some of the flooding columns (preferably all of the flooding columns 192). The extractor of the flood column 192 may comprise an extractor electrode that is common to the electrodes of the extractors 132 of at least some of the electron optical columns 111 (preferably all of the electron optical columns 111). Alternatively, the extractor 132 for each flood column 192 and each electron optical column 111 comprises separate electrode plates. The electrode plates of the flooding column 192 and the electron optical column 111 may be electrically connected to each other and have a common potential. Alternatively, extractors 132 of different columns may be controlled in an individual manner. They may be electrically isolated from each other. Individual control of the extractors 132 can help compensate for performance variations of the emitters 201 of different columns. By adjusting the potential of the extractor 132, the emission variance of the electron source 199 can be reduced.

As shown in fig. 22, in one embodiment, each flood column 192 includes an objective lens. The objective lens is located downstream of the extractor beam. The objective lens may comprise at least one electrode that is common to a plurality of flood columns 192 (preferably, all of the flood columns 192). In one embodiment, at least one electrode of the objective lens of the flood column 192 is common to at least one electrode of the objective lens array 118 of the electron optical column 111. The objective lens is configured to control the size of the spot formed on the surface of the sample 208 by the flood beam. In one embodiment, the objective lens is configured to control the current density on the sample 208. In one embodiment, the controller 50 is configured to switch the electron beam device 40 between a flood mode and an inspection mode. In one embodiment, the switching comprises: the position of the focal point of the objective lens array 118 is changed. The controller 50 may be configured to control the objective lens array 118 to have one focal point for inspection and a different focal point for flood.

As shown in FIG. 22, in one embodiment, each flood column 192 comprises an open angle electrode 193. An open angle electrode 193 is located downstream of the beam of extractor 132. In one embodiment, an open angle electrode 193 is located between the extractor 132 and the objective lens array 118. The opening angle electrode 193 is configured to control a cross section of the electron beam at the objective lens. The opening angle electrode 193 may be common to a plurality of flood columns 192 (preferably, all of the flood columns 192). The opening angle electrode 193 may be common to a plurality of electron optical columns 111 (preferably, all electron optical columns 111). The opening angle of the emitter 201 may be the same as the opening angle of the flood beam for the electron beam used for inspection. Alternatively, the opening angle electrode 193 is not provided. The extractor 132 may be controlled to control the opening angle from the emitter 201.

As shown in fig. 22, in one embodiment, each flood column 192 includes a beam limiting aperture 133. The beam limiting aperture 133 may be located downstream of the beam of the extractor 132 and (if provided) downstream of the beam of the opening angle electrode 193. The beam limiting aperture 133 for the flood column 192 may be formed in the same substrate as the substrate in which the beam limiting aperture 133 for the electron optical column 111 is formed. In one embodiment, the beam limiting aperture 133 for the flood column 192 has a larger size than the beam limiting aperture 133 for the electron optical column 111. Alternatively, the flood column 192 may not be provided with the beam limiting aperture 133.

As shown in fig. 22, in one embodiment, each flood column 192 includes a deflector in the deflector array 134. In one embodiment, the deflector is located between the beam limiting aperture 133 and the objective lens. The deflector is configured to control the position of a beam spot from the flood beam on the sample 208. The deflector array 134 may be common to the flood column 192 and the electron optical column 111.

As shown in fig. 22, in one embodiment, the flood column 192 does not have any detector 170. In one embodiment, the flood column 192 may be similar to the electron optical column 111 except that the flood column 192 does not have the detector 170 and the beam limiting aperture 133 of the flood column 192 is larger.

In one embodiment, the controller 50 is configured to control the flood column 192 so as to control the focus of the flood beam. For example, in one embodiment, the controller 50 is configured to control the objective lens to control the focus of the flood beam. As shown in fig. 22, in one embodiment, the controller 50 is configured to control the flood column 192 such that the focal point of the flood beam is below the surface of the sample 208. The focus may be controlled to be above the surface of the sample 208 or at the surface of the sample 208. By controlling the position of the focal point of the flood beam, the current density of electrons on the surface of the sample 208 can be adjusted.

In one embodiment, a method of operating an electron beam device 40 as described above is provided. The method comprises the following steps: the electron beam emitted by electron source 199 is projected toward sample 208. In one embodiment, the method comprises: the electron beam is directed towards the sample 208 using a respective objective lens. In one embodiment, the method comprises: signal electrons emitted from the sample 208 are detected using a detector 170 associated with the objective lens array 118. This allows the sample 208 to be inspected. Defects in the sample 208 may be detected based on the detected signal electrons.

In one embodiment, the method comprises: a subset of electron emitters 201 is selected from, for example, sources 199 in source array 131 to emit electron beams. The selection may be made electronically. The method comprises the following steps: the electron beams emitted by the subset of electron emitters 201 are projected towards the sample 208. In one embodiment, projecting an electron beam includes: the electron optical column 111 in the column array 200 of the electron optical column 111 is used.

In one embodiment, the method comprises: holding a sample 208 using a sample holder 207; and moving the sample holder 207 and electron optical column 111 relative to each other in the scanning direction 161. In one embodiment, electron optical columns 111 are arranged in parallel lines that are inclined at an angle α to the scan direction 161. In one embodiment, the sample holder 207 and the electron optical column 111 are moved relative to each other such that each electron beam of the electron optical column 111 in one of the parallel lines has a different path on the sample 208. In one embodiment, the sample holder 207 and the electron optical column 111 are moved relative to each other such that each electron beam of the electron optical column 111 has a different path on the sample 208 than all other electron beams of the electron optical column 111.

In one embodiment, a method of scanning a sample 208 includes: the partially overlapping scan partitions are used such that each region is covered on average by at least one other beam. As a result, the redundant coverage of the sample 208 allows compensation of electron beams with defects. In one embodiment, each electron beam has a field of view corresponding to a portion of the surface of the sample 208. The field of view corresponds to a portion that can be reached by the electron beam from the electron optical column 111. The electron beam may be deflected in a direction perpendicular to the beam path such that the electron beam may reach a portion extending in the direction perpendicular to the beam path. In one embodiment, the fields of view of adjacent electron beams partially overlap as the sample holder 207 and electron optical column 111 are moved relative to each other.

In one embodiment, the method comprises: one or more electron beam bands in the electron beam are determined to be defective. The electron beam may be defective due to manufacturing defects. The electron beam may become defective during use. For example, the electron source 199 bombarded with ions may become defective. In one embodiment, an ion trap is provided. The ion trap is configured to trap ions that may adversely affect the electron source 199. The ion trap may comprise electrodes. The ion trap may be integrated with the extractor 132. Ion traps can be made by using planar electron optics in combination with extraction electrodes downstream of the beam of the emitting surface. The planar electron optical device may comprise a conductive semiconductor and/or a resistive semiconductor. Alternatively, the ion trap may comprise a MEMS mirror, a MEMS-based wien filter, or a macromagnetic field generating component.

In one embodiment, the method comprises: the control (e.g., switching off) is determined to be a defective electron beam. The electron beam with defects may be switched off by an electronic control circuit controlling the electron emitter 201 with defective electron beams. The emitters may be electronically selected. Alternatively, the defective electron beam may be effectively cut off by controlling the electron optics of the electron optical column 111 corresponding to the defective electron beam. The electron beam may be electron optically selected. For example, the electron beam with defects may be deflected such that it does not reach the sample 208.

In one embodiment, a method of operating an electron beam device 40 includes: projecting an electron beam emitted by an electron source towards the sample 208; and controlling the electron optical column 111 to selectively (a) shape the respective electron beam through the respective beam limiting aperture 133 such that electrons of the respective electron beam that are less than the threshold current density pass through the respective beam limiting aperture 133; and (b) at least a threshold current density of electrons in at least a proportion of the electron beam pass through the respective beam limiting aperture 133.

In one embodiment, the method comprises: a corresponding plurality of flood beams 192 are used to project a plurality of flood beams toward the sample 208. In one embodiment, the flood beam has a larger electron current than the electron beam projected by the electron optical column 111.

Reference herein to a threshold current density may be a reference to a threshold current. In general, these terms may be considered synonymous or at least overlapping. More precisely, however, in the context disclosed herein, the threshold current density relates to the functionality of the electron beam and the associated charged particle column, and thus to the electron optical properties of the electron beam. The beam current is more related to throughput or the speed at which the sample 209 and electron beam are scanned relative to each other.

Embodiments of the present disclosure may be provided in the form of methods that may use any of the arrangements described above or other arrangements.

References to a component or system that can control a component or element that manipulates a charged particle beam in some way include: the controller or control system or control unit is configured to control the components to manipulate the charged particle beam in the described manner; and optionally other controllers or devices (e.g., voltage supply and/or current supply) control components are used to manipulate the charged particle beam in this manner. For example, under the control of a controller or control system or control unit, a voltage supply may be electrically connected to one or more components to apply an electrical potential to the components (such as the converging aperture 143, converging electrode 144, beam corrector array 145, objective lens array 118, collimator element array, and deflector array 134 in a non-limiting list). One or more controllers, control systems, or control units for controlling actuation of a component may be used to control an actuatable component, such as a stage, to actuate another component, such as a beam path, and thus move relative to the other component.

The embodiments described herein may take the form of a series of aperture arrays or electron-optical elements arranged in an array along a beam or multiple beam paths. Such electron optical elements may be electrostatic. For example, the objective lens array may be an electrostatic lens array. In one embodiment, all electron optical elements (e.g., the last electron optical element in the beam path from the beam limiting aperture array to the sample) may be electrostatic and/or may take the form of an aperture array or a plate array. In some arrangements, one or more of the electron optical elements are fabricated as microelectromechanical systems (MEMS) (i.e., using MEMS fabrication techniques). MEMS are miniaturized mechanical and electromechanical components made using microfabrication techniques. In one embodiment, the replaceable module mentioned above is a MEMS module. Unless explicitly stated otherwise, all electro-optical elements such as arrays of scanning deflectors may be MEMS elements and/or may be fabricated, e.g., formed, using MEMS fabrication techniques.

Where electrodes are provided that can be designed to be of different potentials relative to each other, it will be appreciated that such electrodes will be electrically isolated from each other. In one embodiment, an insulating layer such as an oxide layer or an oxygen-containing nitrate layer is provided to electrically insulate the electrodes from each other. An electrically insulating connector may be provided if the electrodes are mechanically connected to each other. For example, where the electrodes are provided as a series of conductive plates, each defining an array of apertures, e.g. to form an objective lens array or a control lens array, an electrically insulating plate may be provided between the conductive plates. The insulating plate may be connected to the conductive plate so as to serve as an insulating connector. The conductive plates may be separated from each other along the beam path by insulating plates.

References to upper and lower, above and below should be understood to refer to directions parallel (typically but not always perpendicular) to the beam upstream and downstream of the electron beam or beams impinging on the sample 208. Thus, references to upstream and downstream of the beam are intended to refer to directions about the beam path independent of any gravitational field present.

An evaluation system according to embodiments of the present disclosure may be a tool that performs a qualitative evaluation (e.g., pass/fail) of a sample, a tool that performs a quantitative measurement (e.g., size of a feature) of a sample, or a tool that generates a mapped image of a sample. Examples of an evaluation system are an inspection tool (e.g., for identifying defects), an inspection tool (e.g., for classifying defects), and a metrology tool, or a tool capable of performing any combination of evaluation functions associated with an inspection tool, or a metrology tool (e.g., a metrology inspection tool). The electron beam device 40 may be part of an evaluation system, such as an inspection tool or a metrology inspection tool, or an electron beam lithography tool. Any reference herein to a tool is intended to encompass a device, apparatus or system comprising a plurality of components, which may or may not be collocated, and may even be located in a separate room, e.g., for a data processing element.

The terms "beamlet" and "beamlet beam" are used interchangeably herein and are understood to encompass any radiation beam derived from a parent radiation beam by splitting or splitting the parent radiation beam. The term "manipulator" is used to encompass any element affecting the path of the beamlets or sub-beam waves, such as lenses or deflectors.

References to elements aligned along a beam path or sub-beam path should be understood to mean that the respective element is positioned along the beam path or sub-beam path.

According to another aspect of the present invention there is provided a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a plurality of charged particle optical columns configured to project respective charged particle beams towards the sample, wherein each charged particle optical column comprises: a charged particle emitter configured to emit a charged particle beam towards the sample, the charged particle emitter being included in the source array; an objective lens comprising an electrostatic electrode configured to direct a charged particle beam towards a sample, the objective lens being comprised in an objective lens array, the electrostatic electrode being common to a plurality of charged particle optical columns; and a detector associated with the array of objective lenses, the detector configured to detect signal charged particles emitted from the sample, wherein the objective lenses are the beam downstream-most elements of the charged particle optical column configured to affect a charged particle beam directed toward the sample.

According to another aspect of the present invention there is provided a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises: a sample holder configured to hold a sample; a plurality of charged particle optical columns configured to project respective charged particle beams toward the sample, wherein each charged particle optical column comprises a plurality of charged particle emitters configured to emit charged particle beams toward the sample, the charged particle emitters being included in a source array; and preferably an objective lens configured to direct a charged particle beam towards the sample, the objective lens being comprised in an objective lens array; wherein the charged particle beam device is configured such that the sample holder and the charged particle optical column are movable relative to each other in a scanning direction, wherein the charged particle optical column is arranged in parallel lines at an oblique angle to the scanning direction.

According to another aspect of the present invention there is provided a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a plurality of charged particle optical columns configured to project respective charged particle beams towards the sample, wherein each charged particle optical column comprises: a plurality of charged particle emitters configured to emit a charged particle beam toward the sample, the charged particle emitters included in the source array; and preferably an objective lens configured to direct a charged particle beam towards the sample, the objective lens being comprised in an objective lens array; wherein the charged particle emitter comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

According to another aspect of the present invention there is provided a method of operating a charged particle beam apparatus comprising a source array comprising: a charged particle emitter configured to emit a charged particle beam of a plurality of charged particle beams in a charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards the sample, wherein the method comprises: projecting a charged particle beam emitted by a charged particle emitter towards a sample; controlling an electrostatic electrode comprising an objective lens array by applying a potential to at least one of electrodes common to a plurality of charged particle optical columns; directing a charged particle beam towards the sample using a respective objective lens comprising electrostatic electrodes, the objective lens being comprised in an objective lens array; and detecting signal charged particles emitted from the sample using a detector associated with an array of objective lenses, wherein the objective lenses are the beam downstream-most elements of the charged particle optical column configured to affect a charged particle beam directed toward the sample.

According to another aspect of the present invention there is provided a method of operating a charged particle beam apparatus, the charged particle beam apparatus comprising: a source array comprising a charged particle emitter configured to emit a charged particle beam of a plurality of charged particle beams in a charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards the sample, wherein the method comprises: selecting a subset of charged particle emitters from a source array to emit a charged particle beam; and projecting the charged particle beam emitted by the subset of charged particle emitters towards the sample.

According to another aspect of the present invention there is provided a method of operating a charged particle beam apparatus comprising: a source array comprising charged particle sources, each charged particle source configured to emit a charged particle beam, the source array configured to emit a plurality of charged particle beams in a charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards the sample, wherein the method comprises: holding a sample using a sample holder; projecting a charged particle beam emitted by a charged particle source towards the sample, preferably comprising projecting a single charged particle beam towards the sample each using a charged particle optical column; and moving the sample holder and the charged particle optical column relative to each other in a scanning direction; wherein the charged particle optical column is arranged in parallel lines at an oblique angle to the scanning direction.

According to another aspect of the present invention there is provided a method of operating a charged particle beam apparatus comprising a source array comprising a charged particle source configured to emit a charged particle beam of a plurality of charged particle beams in the charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards the sample, wherein the method comprises: projecting a charged particle beam emitted by a charged particle source towards the sample; wherein the charged particle source comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

According to another aspect of the present invention there is provided a method of operating a charged particle beam apparatus, the charged particle beam apparatus comprising: a source array comprising a charged particle source configured to emit a charged particle beam of a plurality of charged particle beams in a charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards the sample, wherein each charged particle optical column comprises a beam limiting aperture configured to select a cross section of the charged particle beam to be projected towards the sample, wherein the method comprises: projecting a charged particle beam emitted by a charged particle source towards the sample; and controlling the charged particle optical column such that selectively: (a) The respective charged particle beam is shaped by the respective beam limiting aperture such that charged particles of the respective charged particle beam that are less than the threshold current density pass through the respective beam limiting aperture, and (b) at least a threshold current density of charged particles in at least a proportion of the charged particle beam pass through the respective beam limiting aperture.

According to another aspect of the present invention there is provided a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises: a source array comprising a plurality of charged particle emitters configured to emit respective charged particle beams; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project corresponding respective charged particle beams emitted by the charged particle sources of the source array towards the sample, wherein each charged particle optical column comprises an objective lens comprising an electrostatic electrode configured to direct the charged particle beam towards the sample, the objective lens being comprised in the objective lens array, and a detector associated with the objective lens array and configured to detect signal charged particles emitted from the sample; wherein the objective lens is a beam downstream-most element of the charged particle optical column configured to affect a charged particle beam directed towards the sample.

According to another aspect of the present invention there is provided a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises: a source array comprising a plurality of charged particle emitters configured to emit respective charged particle beams; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project corresponding respective charged particle beams emitted by the charged particle sources of the source array towards the sample, wherein each charged particle optical column comprises an objective lens configured to direct a charged particle beam towards the sample, the objective lens being comprised in the objective lens array; wherein the charged particle emitters are configured to be selectable such that a subset of the charged particle emitters may be selected to emit a charged particle beam toward the substrate.

According to another aspect of the present invention there is provided a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a sample holder configured to hold the sample; a source array comprising a plurality of charged particle sources configured to emit respective charged particle beams; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to direct a corresponding respective charged particle beam emitted by a charged particle source towards the sample projection source array, wherein the charged particle beam device is configured such that the sample holder and the charged particle optical columns are movable relative to each other in a scanning direction, wherein each charged particle optical column optionally comprises an objective lens configured to direct the charged particle beam towards the sample, the objective lens being comprised in the objective lens array; wherein the charged particle optical columns are arranged in a pattern in which parallel lines of the charged particle optical columns are inclined at an angle to the scanning direction.

According to another aspect of the present invention there is provided a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises: a source array comprising a plurality of charged particle sources configured to emit respective charged particle beams; a charged particle optical column array comprising a plurality of charged particle optical columns configured to project corresponding respective charged particle beams emitted towards a charged particle source of the sample projection source array, wherein each charged particle optical column optionally comprises an objective lens configured to project a charged particle beam towards the sample, the objective lens being comprised in the objective lens array; wherein the charged particle source comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

While the invention has been described in conjunction with various embodiments, other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and clauses.

The following clauses are provided. Clause 1: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a plurality of charged particle optical columns configured to project respective charged particle beams towards the sample, wherein each charged particle optical column comprises: a charged particle emitter configured to emit the charged particle beam toward the sample, the charged particle emitter included in a source array; an objective lens comprising an electrostatic electrode configured to direct the charged particle beam towards the sample, the objective lens being comprised in an objective lens array, the electrostatic electrode being common to a plurality of the charged particle optical columns; and a detector associated with the array of objective lenses, the detector configured to detect signal charged particles emitted from the sample, wherein the objective lens is a beam downstream-most element of the charged particle optical column, the beam downstream-most element configured to affect the charged particle beam directed toward the sample.

Clause 2: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a plurality of charged particle optical columns capable of being arranged in an array of charged particle optical columns configured to project respective charged particle beams towards the sample, wherein each charged particle optical column comprises: a plurality of charged particle emitters configured to emit the charged particle beam toward the sample, the charged particle emitters included in a source array; and preferably an objective lens configured to direct the charged particle beam towards the sample, ideally an electrostatic objective lens, the objective lens being comprised in an objective lens array, the objective lens ideally having different charged particle optical columns of the plurality of charged particle optical columns; wherein the charged particle emitters are configured to be selectable such that a subset of the charged particle emitters can be selected to emit the charged particle beam toward the sample.

Clause 3: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises: a plurality of charged particle optical columns configured to project respective charged particle beams toward the sample, wherein each charged particle optical column comprises: a source in a source array, the source comprising a plurality of charged particle emitters configured to emit the charged particle beam toward the sample, each source comprising a number of the emitters of the plurality of emitters; a beam limiting aperture configured to select a cross section of the charged particle beam to be projected towards the sample, wherein the charged particle emitter is configured to be selectable such that a subset of the charged particle emitters can be selected to emit the charged particle beam towards the sample, and upon selection of the subset of the charged particle emitters, the emitted charged particle beam has different ones of the plurality of charged particle columns and the sources of respective different ones of the charged particle columns. Ideally, the emitter is in the substrate. The emitters may be in a planar array. The substrate is planar. The source array includes an extractor for each column. Ideally, the source array comprises an extractor array. Ideally, the source may be selected by controlling the operation of the emitters within the group of each column. The source array includes control circuitry controllable to select a subset of the emitter groups of pillars. The transmitters within the group are addressable. The control circuit enables the addressable transmitters to enable one or more transmitters in the set of transmitters to be operated in a controllable manner. The deflector can be controllable to select one or more emitters from a group of emitters and/or to direct the charged particle beam from the one or more emitters in the group of emitters that are controlled to operate. Each extractor of the source of the column can have one or more emitters. Ideally, there can be one or more emitters for each beam limiting aperture of a column of the plurality of columns.

Clause 4: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises: a sample holder configured to hold the sample; a plurality of charged particle optical columns configured to project respective charged particle beams towards the sample, wherein each charged particle optical column comprises a plurality of charged particle emitters configured to emit the charged particle beams towards the sample, the charged particle emitters being included in a source array; and preferably an objective lens configured to direct the charged particle beam towards the sample, the objective lens being comprised in an objective lens array; wherein the charged particle beam device is configured such that the sample holder and the charged particle optical column are movable relative to each other in a scanning direction, wherein the charged particle optical column is arranged in parallel lines at an oblique angle to the scanning direction.

Clause 5: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a plurality of charged particle optical columns configured to project respective charged particle beams towards the sample, wherein each charged particle optical column comprises a plurality of charged particle emitters configured to emit the charged particle beams towards the sample, a charged particle source being included in a source array; and preferably an objective lens configured to direct the charged particle beam towards the sample, the objective lens being comprised in an objective lens array; wherein the charged particle emitter comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

Clause 6: the charged particle beam apparatus of any of clauses 1-4, wherein the charged particle emitter comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

Clause 7: the charged particle beam apparatus of any of clauses 1,2, 3, or 5, wherein the charged particle beam apparatus is configured such that the sample holder and the charged particle optical column are movable relative to each other in a scanning direction; and the charged particle optical columns are arranged in parallel lines at an oblique angle to the scanning direction.

Clause 8: the charged particle beam apparatus of any of clauses 1, 4, or 5, wherein each charged particle optical column comprises a plurality of the charged particle emitters; and the charged particle emitters are configured to be selectable such that a subset of the charged particle emitters can be selected to emit the charged particle beam toward the substrate.

Clause 9: a charged particle beam device according to any of clauses 2-5, wherein each objective lens comprises an electrostatic electrode common to a plurality of the charged particle optical columns; each charged particle optical column includes a detector associated with the objective lens array, the detector configured to detect signal charged particles emitted from the sample; wherein the objective lens is a beam downstream-most element of the charged particle optical column configured to affect the charged particle beam directed towards the sample.

Clause 10: the charged particle beam apparatus of clause 1 or 9, wherein the electrostatic electrode is common to all of the charged particle optical columns.

Clause 11: the charged particle beam apparatus of clause 4 or 7, wherein each charged particle beam has a field of view corresponding to a portion of the surface of the sample, preferably wherein the fields of view of adjacent charged particle beams partially overlap when the sample holder and the charged particle optical column are moved relative to each other.

Clause 12: a charged particle beam apparatus according to any preceding clause, wherein each charged particle optical column comprises an extractor configured to increase emission from the charged particle emitter.

Clause 13: the charged particle beam apparatus of clause 12, wherein the extractor comprises an extractor electrode common to all of the charged particle optical columns.

Clause 14: charged particle beam apparatus according to any of the preceding clauses, wherein each charged particle optical column comprises a beam limiting aperture configured to select a cross section of the charged particle beam to be projected towards the sample, preferably wherein the beam limiting aperture is defined in a plate common to a plurality of the charged particle optical columns, preferably all the charged particle optical columns.

Clause 15: the charged particle beam apparatus of clause 14, comprising a controller configured to control the charged particle optical column such that selectively: (a) The respective charged particle beam is shaped by the respective beam limiting aperture such that charged particles of the respective charged particle beam that are less than a threshold current density pass through the respective beam limiting aperture, and (b) at least a proportion of charged particles of the charged particle beam that are at least the threshold current density pass through the respective beam limiting aperture.

Clause 16: the charged particle beam apparatus of clause 15, wherein the controller is configured to control the charged particle beam apparatus to perform flooding of the surface of the sample when at least the threshold current density of at least a proportion of the charged particle beams passes through the respective beam limiting aperture.

Clause 17: the charged particle beam apparatus of clause 15 or 16, wherein each charged particle optical column comprises a detector configured to detect signal charged particles emitted from the sample; and the controller is configured to control the charged particle beam apparatus to operate to detect signal charged particles emitted by the sample as the respective charged particle beam is shaped by the respective beam limiting aperture such that charged particles of the respective charged particle beam that are less than a threshold current density pass through the respective beam limiting aperture.

Clause 18: the charged particle beam apparatus of any of clauses 15-17, wherein each charged particle optical column comprises an extractor common to at least the proportion of the charged particle optical columns, preferably the charged particle optical columns, wherein the extractor is located between the emitter and the beam limiting aperture; and the controller is configured to control the voltages applied to the extractors so as to control the opening angles of the corresponding charged particle beams from the emitters toward the beam limiting apertures so as to control the extent to which the corresponding charged particle beams are shaped by the respective beam limiting apertures.

Clause 19: the charged particle beam apparatus of any of clauses 15-18, wherein each charged particle optical column comprises an open angle electrode common to at least the proportion of the charged particle optical columns, preferably the charged particle optical columns, wherein the open angle electrode is located between the emitter and the beam limiting aperture; and the controller is configured to control the voltages applied to the opening angle electrodes so as to control the opening angle of the corresponding charged particle beam from the emitter towards the beam limiting aperture so as to control the extent to which the corresponding charged particle beam is shaped by the respective beam limiting aperture.

Clause 20: the charged particle beam apparatus of any of clauses 15-19, comprising a plurality of flood columns configured to project respective flood charged particle beams toward the sample, wherein each flood column comprises at least one charged particle emitter configured to emit the flood beams toward the sample and is included in the source array; wherein the flood column is configured to project a greater charged particle current onto the sample than the charged particle optical column.

Clause 21: the charged particle beam apparatus of any of clauses 15-20, wherein the flood columns are interspersed between the charged particle optical columns.

Clause 22: the charged particle beam apparatus of clause 20 or 21, wherein the flood column is positioned adjacent to a respective charged particle optical column.

Clause 23: the charged particle beam apparatus of any of clauses 22, wherein the charged particle optical columns are arranged in a grid.

Clause 24: the charged particle beam apparatus of clause 23, wherein the flood columns are arranged in a pattern wherein the flood columns are substantially equidistant between at least two adjacent charged particle optical columns, preferably between three adjacent charged particle optical columns.

Clause 25: the charged particle beam apparatus of clause 23 or 24, wherein the flood column is arranged in a grid similar to the grid of the charged particle optical column, and the flood column is offset relative to the grid of the charged particle optical column so as to: along a line between two adjacent charged particle optical columns in the grid of the charged particle optical columns, or with three adjacent charged particle optical columns spaced apart within a similar displacement range.

Clause 26: the charged particle beam apparatus of any of clauses 23-25, comprising an actuator configured to actuate a sample holder in an orthogonal actuation direction relative to the charged particle optical column, the sample holder configured to hold the sample; and the flood column is positioned relative to the respective charged-particle optical column in at least one of the actuation directions.

Clause 27: the charged particle beam device of any of clauses 20-25, wherein the number of flood columns is equal to or less than the number of charged particle optical columns.

Clause 28: a charged particle beam apparatus according to any preceding clause, wherein each charged particle optical column comprises a deflector configured to deflect the charged particle beam in a direction perpendicular to the axis of the charged particle optical column, preferably the deflector is comprised in a deflector array of deflectors for at least one group of the charged particle optical columns.

Clause 29: a charged particle beam apparatus according to any preceding clause, wherein each charged particle optical column comprises a converging lens configured to operate on the charged particle beam.

Clause 30: the charged particle beam apparatus of clause 29, wherein the converging lens comprises at least one converging electrode that is common to all of the charged particle optical columns.

Clause 31: a charged particle beam apparatus according to any preceding clause, wherein each charged particle optical column comprises an individual beam corrector configured to correct characteristics of the charged particle beam, preferably the corrector is comprised in a beam corrector array for at least one group of the charged particle optical columns.

Clause 32: a charged particle beam apparatus according to any preceding clause, wherein the charged particle emitter is semiconductor-based.

Clause 33: the charged particle beam apparatus of any clause, wherein the charged particle emitter comprises an avalanche diode structure.

Clause 34: a charged particle beam apparatus according to any clause, wherein the source array is dimensioned such that the charged particle emitter extends across at least a portion of the sample, ideally across a substantial portion of the sample, preferably across substantially all of the sample.

Clause 35: a charged particle device according to any clause, wherein the source array comprises a plurality of sources, each source comprising a plurality of the emitters, and each source is assigned to one of the electron optical columns, ideally each source belongs to one of the electron optical columns.

Clause 36: a method of operating a charged particle beam apparatus comprising a source array comprising a charged particle emitter configured to emit a charged particle beam of a plurality of charged particle beams in a charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards a sample, wherein the method comprises: projecting the charged particle beam emitted by the charged particle emitter towards the sample; controlling, using respective objective lenses comprising electrostatic electrodes, the electrostatic electrodes comprising an array of objective lenses by applying a potential to at least one of the electrodes common to a plurality of the charged particle optical columns, the objective lenses being comprised in the array of objective lenses, the charged particle beams being directed towards the sample; and detecting signal charged particles emitted from the sample using a detector associated with the array of objective lenses, wherein the objective lenses are a beam downstream-most element of the charged particle optical column configured to affect the charged particle beam directed toward the sample.

Clause 37: a method of operating a charged particle beam apparatus, the charged particle beam apparatus comprising: a source array comprising a charged particle emitter configured to emit a charged particle beam of a plurality of charged particle beams in a charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards a sample, wherein the method comprises: selecting a subset of charged particle emitters from the source array to emit the charged particle beam; and projecting the charged particle beam emitted by the subset of charged particle emitters toward the sample.

Clause 38: the method of clause 37, wherein the projecting the charged particle beam comprises: the charged particle optical column in the charged particle optical column array is used.

Clause 39: a method of operating a charged particle beam apparatus comprising a source array comprising charged particle sources, each charged particle source configured to emit a charged particle beam, the source array configured to emit a plurality of the charged particle beams in the charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards a sample, wherein the method comprises: holding the sample using a sample holder; projecting the charged particle beam emitted by the charged particle source towards the sample, preferably comprising using the charged particle optical columns, each charged particle optical column projecting a single charged particle beam towards the sample; and moving the sample holder and the charged particle optical column relative to each other in a scanning direction; wherein the charged particle optical column is arranged in parallel lines at an oblique angle to the scanning direction.

Clause 40: the method of clause 39, wherein the sample holder and the charged particle optical column are moved relative to each other such that each charged particle beam of the charged particle optical column in one of the parallel lines has a different path on the sample.

Clause 41: the method of clause 40, wherein the sample holder and the charged particle optical column are moved relative to each other such that each charged particle beam of the charged particle optical column has a different path on the sample than all other charged particle beams of the charged particle optical column.

Clause 42: a method of operating a charged particle beam apparatus, the charged particle beam apparatus comprising: a source array comprising a charged particle source configured to emit a charged particle beam of a plurality of charged particle beams in a charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards a sample, wherein the method comprises: projecting the charged particle beam emitted by the charged particle source towards the sample; wherein the charged particle source comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

Clause 43: a method of operating a charged particle beam apparatus comprising a source array comprising a charged particle source configured to emit a charged particle beam of a plurality of charged particle beams in the charged particle beam array; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project respective charged particle beams from the source array towards a sample, wherein each charged particle optical column comprises a beam limiting aperture configured to select a cross section of the charged particle beam to be projected towards the sample, wherein the method comprises: projecting the charged particle beam emitted by a charged particle source towards the sample; and controlling the charged particle optical column to selectively: (a) The respective charged particle beam is shaped by the respective beam limiting aperture such that charged particles of the respective charged particle beam that are less than a threshold current density pass through the respective beam limiting aperture, and (b) at least a proportion of charged particles of the charged particle beam that are at least the threshold current density pass through the respective beam limiting aperture.

Clause 44: the method according to clause 43, comprising: a plurality of flood charged particle beams are projected toward the sample using a respective plurality of flood columns, wherein the flood beams have a greater charged particle current than the charged particle beams projected by the charged particle optical columns.

Clause 45: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a source array comprising a plurality of charged particle sources configured to emit respective charged particle beams; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project a corresponding respective charged particle beam emitted by a charged particle source of the source array towards the sample, wherein each charged particle optical column comprises an objective lens comprising an electrostatic electrode configured to direct the charged particle beam towards the sample, the objective lens being comprised in an array of objective lenses, and a detector associated with the array of objective lenses and configured to detect signal charged particles emitted from the sample; wherein the objective lens is a beam downstream-most element of the charged particle optical column configured to affect the charged particle beam directed towards the sample.

Clause 46: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a source array comprising a plurality of charged particle emitters configured to emit respective charged particle beams; a charged particle optical column array comprising a plurality of charged particle optical columns configured to project corresponding respective charged particle beams emitted by a charged particle source of the source array towards the sample, wherein each charged particle optical column optionally comprises an objective lens configured to direct the charged particle beam towards the sample, the objective lens being comprised in an objective lens array; wherein the charged particle emitters are configured to be selectable such that a subset of the charged particle emitters can be selected to emit the charged particle beam toward the substrate.

Clause 47: the charged particle beam apparatus of clause 46, wherein each charged particle source in the subset corresponds to a charged particle optical column in the array of charged particle optical columns, ideally each charged particle emitter in the subset belongs to a charged particle optical column in the array of charged particle optical columns.

Clause 48: the charged particle beam apparatus of clause 46 or 47, wherein the number of charged particle sources in the subset is the same as the number of charged particle optical columns in the array of charged particle optical columns.

Clause 49: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a sample holder configured to hold the sample; a source array comprising a plurality of charged particle sources configured to emit respective charged particle beams; and an array of charged particle optical columns comprising a plurality of charged particle optical columns configured to project corresponding respective charged particle beams emitted by a charged particle source of the source array towards the sample, wherein the charged particle beam device is configured such that the sample holder and the charged particle optical columns are movable relative to each other in a scanning direction, wherein each charged particle optical column optionally comprises an objective lens configured to direct the charged particle beam towards the sample, the objective lens being comprised in an objective lens array; wherein the charged particle optical columns are arranged in a pattern in which parallel lines of the charged particle optical columns are at an oblique angle to the scanning direction.

Clause 50: a charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises a source array comprising a plurality of charged particle sources configured to emit respective charged particle beams; a charged particle optical column array comprising a plurality of charged particle optical columns configured to project corresponding respective charged particle beams emitted by a charged particle source of the source array towards the sample, wherein each charged particle optical column optionally comprises an objective lens configured to direct the charged particle beam towards the sample, the objective lens being comprised in an objective lens array; wherein the charged particle source comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

The above description is intended to be illustrative, and not restrictive. It will therefore be apparent to those skilled in the art that modifications may be made in accordance with the description without departing from the scope of the claims set out below.

Claims (15)

1. A charged particle beam apparatus configured to project a charged particle beam towards a sample, wherein the charged particle beam apparatus comprises:

A plurality of charged particle optical columns arranged in an array of charged particle optical columns configured to project respective charged particle beams toward the sample, wherein each charged particle optical column comprises:

a plurality of charged particle emitters configured to emit the charged particle beam toward the sample, the charged particle emitters included in a source array; and

An objective lens configured to direct the charged particle beam towards the sample, the objective lens being an electrostatic objective lens, the objective lens being comprised in an objective lens array,

Wherein the charged particle emitters are configured to be selectable such that a subset of the charged particle emitters can be selected to emit the charged particle beam toward the sample.

2. Charged particle beam apparatus according to claim 1, wherein the emitters are selectable by selectively operating the emitters in the source array.

3. Charged particle beam apparatus according to claim 1 or 2, wherein the emitters are selectable by deflecting the electron beam from a selected emitter towards the beam path in the electron optical column.

4. A charged particle beam apparatus according to any one of claims 1 to 3, further comprising an array of deflectors associated with the charged particle emitter, wherein each deflector in the array of deflectors is configured to deflect charged particles emitted by a charged particle emitter in the source array so that the path of the charged particles is along the axis of the electron optical column.

5. A charged particle beam apparatus according to any preceding claim wherein each charged particle emitter in the subset corresponds to a charged particle optical column in the array of charged particle optical columns, ideally belonging to a charged particle optical column in the array of charged particle optical columns.

6. A charged particle beam apparatus according to any preceding claim wherein the number of charged particle emitters in the subset is the same as the number of charged particle optical columns in the array of charged particle optical columns.

7. A charged particle device according to any preceding claim, wherein the array of sources comprises a plurality of sources, each source comprising the plurality of emitters, and each source being assigned to one of the electron optical columns, ideally each source belonging to one of the electron optical columns.

8. Charged particle beam apparatus according to any preceding claim, wherein the source array is dimensioned such that the charged particle emitter extends across at least a portion of the sample, ideally across a majority of the sample, preferably substantially all of the sample.

9. Charged particle beam apparatus according to any one of the preceding claims, wherein the charged particle emitter comprises an avalanche diode structure.

10. Charged particle beam apparatus according to any preceding claim, wherein the charged particle emitter comprises at least one selected from the group consisting of: silicon carbide, gallium nitride, aluminum nitride, and boron nitride.

11. A charged particle beam apparatus according to any preceding claim wherein each charged particle optical column comprises an extractor configured to increase emission from the charged particle emitter, wherein the extractor comprises an extractor electrode common to all of the charged particle optical columns.

12. Charged particle beam apparatus according to any preceding claim, wherein

Each objective lens comprises an electrostatic electrode common to a plurality of said charged particle optical columns; and

Each charged particle optical column includes a detector associated with the objective lens array, the detector configured to detect signal charged particles emitted from the sample;

Wherein the objective lens is a beam downstream-most element of the charged particle optical column configured to affect the charged particle beam directed towards the sample.

13. The charged particle beam apparatus of claim 12, wherein the electrostatic electrode is common to all of the charged particle optical columns.

14. Charged particle beam apparatus according to any preceding claim, wherein each charged particle optical column comprises an individual beam corrector configured to correct characteristics of the charged particle beam, preferably the corrector is comprised in a beam corrector array for at least one group of the charged particle optical columns.

15. Charged particle beam apparatus according to any preceding claim, wherein

The charged particle beam device is configured such that the sample holder and the charged particle optical column are movable relative to each other in a scanning direction; and

The charged particle optical columns are arranged in parallel lines at an oblique angle to the scanning direction.