CN116018612A

CN116018612A - Method for defect inspection measurement of a substrate, apparatus for imaging a substrate and method for operating the same

Info

Publication number: CN116018612A
Application number: CN202080104034.9A
Authority: CN
Inventors: 伯纳德·G·穆勒; 尼古拉·克努布
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2020-08-11
Filing date: 2020-08-11
Publication date: 2023-04-25
Also published as: TW202212813A; TWI789863B; KR20230048409A; WO2022033661A1

Abstract

A method for performing defect inspection measurements on a substrate is described. The method includes generating a defect image of a substrate portion including a defect; generating a reference image corresponding to the defect image; determining a mask pattern based on the reference image; and comparing the defect image with the reference image in an area outside the mask pattern to detect a defect.

Description

Method for defect inspection measurement of a substrate, apparatus for imaging a substrate and method for operating the same

Technical Field

The present disclosure relates to an apparatus and method for imaging a substrate. More particularly, embodiments described herein relate to a method for performing Defect Review (DR) measurements on a substrate, particularly for display manufacturing, such as a large area substrate. In particular, embodiments relate to a method for performing defect inspection measurements on a substrate, an apparatus for imaging a substrate, and a method of operating the same.

Background

In many applications, it is beneficial to inspect a substrate to monitor the quality of multiple substrates. For example, glass substrates with a layer of coating material deposited thereon are manufactured for the display market. Since defects may occur, for example, during substrate processing, such as during substrate coating, it is beneficial to inspect the substrate to inspect the defects and monitor the quality of the display.

Displays are often fabricated on large area substrates with ever-increasing substrate sizes. In addition, displays, such as TFT displays, are continually improving. Inspection of the substrate may be performed by an optical system. However, defect Review (DR) measurements, such as those of TFT arrays, require resolution not provided by optical inspection. DR measurements may, for example, characterize defects that have been previously detected. Thus, DR measurements are valuable for process control because countermeasures to prevent or reduce the probability of defects can be taken.

By comparing the reference image with the defect image, i.e. the image to be inspected, defect detection or re-detection in the "defect inspection system" may be provided. A defect is considered to be a deviation between the reference image and the defect image exceeding a given threshold.

The substrate for display manufacturing is typically of an area of, for example, 1m ² Or a larger glass substrate. High resolution images on such large substrates are very challenging in themselves and most findings from the wafer industry are not applicable. Furthermore, the options for DR measurement illustratively described above may not be applicable to large area substrates.

In the display industry, deviations between images of specific locations of display products exhibit significant deviations due to process variations based on manufacturing tolerances of display manufacturing. Manufacturing tolerances for display manufacturing may be higher compared to semiconductor manufacturing on a wafer, due to the much larger area compared to semiconductor manufacturing. In particular, the edge roughness of the pattern structure may lead to the fact that defect inspection procedures from the wafer industry may not provide the desired results. Such deviations may lead to false defect detection or to low threshold settings, which in turn may lead to low detection sensitivity. In general, manufacturing tolerances on the same order of magnitude or close to the order of magnitude may result in false defect detection or low threshold settings as compared to the size of the defect to be detected.

Thus, in view of, for example, the increasing demand for defect inspection quality, there is a need for an improved apparatus and method for imaging a substrate, such as not mashing the substrate into smaller samples and allowing the manufacturing process of the substrate to continue after DR measurements.

Disclosure of Invention

In view of the foregoing, a method for performing defect inspection measurements on a substrate, an apparatus for imaging at least a portion of a substrate, and a method of operating the apparatus are provided. Other aspects, advantages, and features of the present disclosure will be apparent from the description and drawings.

According to one embodiment, a method for performing defect inspection measurements on a substrate is provided. The method includes generating a defect image of a substrate portion including a defect; generating a reference image corresponding to the defect image; determining a mask pattern based on the reference image; and comparing the defect image with the reference image in an area outside the mask pattern to detect a defect.

According to one embodiment, an apparatus for imaging a portion of a substrate is provided. The apparatus includes a vacuum chamber, a substrate support disposed in the vacuum chamber, and a first imaging charged particle beam microscope. The controller includes a processor and a memory storing instructions that, when executed by the processor, cause the device to perform a method according to any of the embodiments described herein.

According to one embodiment, a method of operating an apparatus according to any of the embodiments described herein is provided. The method includes matching a first coordinate system on a substrate of a first imaging charged particle beam microscope with a second coordinate system on a substrate of a second imaging charged particle beam microscope.

Drawings

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, for the may admit to other equally effective embodiments.

Fig. 1A to 1C illustrate images for explaining defect inspection measurement according to an embodiment of the present disclosure.

Fig. 2 illustrates a side view of an apparatus for imaging a portion of a substrate according to embodiments described herein.

Fig. 3 illustrates a side view of another apparatus for imaging a portion of a substrate according to embodiments described herein.

Fig. 4 illustrates a side view of an imaging charged particle beam microscope, i.e., an exemplary apparatus for inspecting imaging of a portion of a substrate, according to embodiments described herein.

Fig. 5 illustrates a flow chart illustrating a method for defect inspection measurement, particularly for large area substrates, such as for display manufacturing, in accordance with an embodiment of the present disclosure.

Fig. 6A-6E illustrate exemplary images of defect inspection measurements according to embodiments of the present disclosure.

Fig. 7A to 7C illustrate pictures for explaining images corresponding to the defect inspection measurement of fig. 1A to 1C.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

Detailed Description

Reference will now be made in detail to the various exemplary embodiments, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation, and not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present disclosure include such modifications and variations.

In the following description of the drawings, like reference numerals refer to like parts. Only the differences with respect to the respective embodiments are described. The structures shown in the drawings are not necessarily true to scale but rather serve to better understand the embodiments.

Electron beam inspection (electron beam review, EBR) is a relatively young technique, particularly for large area substrates, in which the entire substrate or areas distributed over the entire substrate are measured such that, for example, the display to be manufactured is not destroyed during the inspection process or when used in the inspection process. For example, a resolution of 20nm or less, such as 10nm or less, is very difficult to achieve and previous findings from wafer imaging may not be suitable in view of the significant differences in substrate size. For example, a stage, i.e. a substrate stage, may advantageously be adapted to be positioned in any area of the entire substrate below the electron beam, and the positioning over a large area has to be very accurate. For large area substrates, the area to be measured is larger, for example, compared to a wafer imaging device, and the various areas may be further apart from each other. Thus, simple scale-up is unsuccessful, for example due to different throughput requirements. Furthermore, the process and apparatus are advantageously adapted to reduce vibrations over large dimensions below the required resolution. Furthermore, manual or semi-automated processes may also be unsuitable in view of the required throughput and repeatability of measurement locations distributed over the area of the large area substrate.

In addition, manufacturing tolerances for display fabrication on large area substrates are larger than for semiconductor fabrication on wafers. Thus, the acceptable deviation of the image at the first location from the image at the second location with the same pattern is greater than in semiconductor manufacturing. Thus, the size of the defect may be within the same order of magnitude as the acceptable deviation, or the size of the defect may be only one or two orders of magnitude greater than the acceptable deviation. In general, for display manufacturing and in the semiconductor industry, defect inspection may be based on image comparison and thresholds of image deviation. This comparison is limited as long as the defect size is close to the magnitude of acceptable deviations, e.g. deviations based on manufacturing tolerances. Accordingly, embodiments of the present disclosure are particularly directed to defect inspection for display manufacturing, for example, to detect defects on large area substrates. Furthermore, embodiments of the present disclosure may also relate to the semiconductor industry, where defects are small compared to manufacturing tolerances, in particular on the same order of magnitude or only one or two orders of magnitude larger. Embodiments of the present disclosure provide an improved defect inspection metrology.

Embodiments of the present disclosure relate to defect inspection based on image comparison, such as comparison of a defect image including a defect at one pixel of a display (e.g., a transistor of a TFT display) with a reference image at an adjacent pixel, or based on comparison of one die with an adjacent die. The term "adjacent" may refer to directly adjacent structures or immediately adjacent structures having the same pattern of patterned thin film. Directly adjacent structures may also be referred to as structures adjacent to defective structures. Within the array area (display area) the feature (pixel) structure is repeated or repeated for the unit cell. The unit cell is the smallest group of structures that repeat periodically in the display array area. For example, a unit cell is a set of red, green and blue (RGB) pixel structures, or nxrgb. One structure within a unit cell is equal to an equivalent structure within any other unit cell. Any unit cell structure may be used as a reference for comparison with a unit cell comprising a defect candidate to be detected and inspected. According to some embodiments, which may be combined with other embodiments described herein, the defect image may be generated at one unit cell and the reference image may be generated at another unit cell. For example, another unit cell of the reference image may be a neighboring unit cell (including second, third, fourth, etc., neighboring unit cells) or a directly neighboring unit cell.

According to embodiments of the present disclosure, pattern edges in a reference image are utilized to create a mask, i.e., a mask pattern, which is formed to have pattern edges of a defined size. The reference image and the defect image are compared. For example, the luminance difference may be calculated. The mask pattern is overlaid on the pattern edges, i.e. the masked areas are ignored by defect detection. Defect candidates of the defect image are selected. For example, the best defect candidate or one or more defect candidates, i.e. deviations of the structure outside the mask pattern, may be selected. Without the mask pattern, the areas of one or more defect candidates are again evaluated for defect detection.

Fig. 1A-1C illustrate an exemplary embodiment of a method for defect inspection measurement. Corresponding picture icons of fig. 1A-1C are in fig. 7A-7C, with some of the features being additionally labeled with reference numerals A, B and C. Fig. 1A illustrates a reference image 10. For example, the image may include a portion of a thin film transistor of a pixel of a display. The image may be a scanning electron microscope image. For example, signal electrons generated when an electron strikes the substrate are measured, i.e., the signal intensity can be measured. The intensity signal of the signal electronics may be displayed to generate an image. The reference image 10 illustrates a structure 14. Structure 14 corresponds to a structure manufactured during display manufacturing. According to some embodiments, which may be combined with other embodiments described herein, the reference image 10 may also include features 12 (see also reference numeral C in fig. 7A). The feature 12 may be an undesirable or strange feature that may not cause defects but is not intended for a perfectly fabricated structure 14.

Fig. 1B illustrates a defect image. The defect image includes defects 22. Some operations of a method for performing defect inspection measurements on a substrate according to embodiments of the present disclosure are illustrated in fig. 1C. A comparison between the reference image 10 and the defect image 20 is calculated. The comparison image 30 is generated, for example, by calculating the luminance difference between the reference image 10 and the defect image 20. For example, a perfectly matched defect image and reference image will result in a black comparison image, i.e. an image without bias. The difference between the reference image and the defective image appears as a bright spot, i.e., a luminance deviation. For example, the absolute value of the difference between the reference image and the defect image may be calculated and/or plotted. The larger the deviation of the intensity signal, the larger the absolute difference and thus the brighter the area in the comparison image. According to some embodiments, which may be combined with other embodiments described herein, the comparison image may additionally or alternatively be generated by a filter and a further image processing procedure, wherein the defect image and the reference image are compared.

The mask pattern 32 is overlaid on the comparison image 30. The mask pattern 32 is generated from the structure 14 of the reference image 10. According to embodiments of the present disclosure, the structure may include one or more features selected from the group consisting of: vias, lines, trenches, connections, material boundaries, etched layer structures, etc. According to some embodiments, which may be combined with other embodiments described herein, the structure may be part of a thin film transistor or another transistor for operating a pixel of the display.

According to some embodiments, which may be combined with other embodiments described herein, the mask pattern 32 is generated by a pattern recognition method.

According to some embodiments, which may be combined with other embodiments described herein, the mask pattern 32 may include features 12, i.e., strange features of the reference image 10. Because the feature 12 is not intentional, it may result in a difference in brightness between the reference image and the defective image. However, since the reference image does not include defects, the brightness difference corresponding to the feature 12 may result in incorrect defect detection. The comparison image 30 is masked by the mask pattern 32 and the areas of the mask pattern are ignored. Thus, the mask pattern including features 12 prevents false defect detection of strange features.

Additionally or alternatively, the brightness differences 24 (see also reference B in fig. 7B) caused by manufacturing tolerances, such as edge roughness or other manufacturing tolerances, that may generate false defect detection in the comparison image 30 are obscured by the mask pattern 32. Thus, an acceptable deviation of an image at a first location (e.g., reference image 10) relative to an image at a second location (e.g., defect image 20 having the same pattern) may not result in a defect alarm because the acceptable deviation is obscured by mask pattern 32.

As shown in fig. 1C, the defect 22 (see also reference sign a in fig. 7C) illustrates the luminance difference between the reference image 10 and the defect image 20. The defect 22 is outside the mask pattern 32. The comparison of the defect image in the area outside the mask pattern with the reference image is used to detect defects 22. According to some embodiments, which may be combined with other embodiments described herein, the comparison image 30 is searched for one or more best defect candidates outside the mask pattern. After one or more defects are detected, such as defect 22 in FIG. 1C, defect detection at the location of the defect may be further provided without mask pattern 32.

The multi-step method includes defect selection using a mask pattern and further defect re-inspection of the selected defect without the mask pattern as several advantages. Such advantages may be tailored to the manufacturing conditions of the display. More pronounced pattern edge roughness in display fabrication does not lead to false defects. Due to the masking, defects in the remaining area of the image, i.e. the non-masked area, can be searched for with a higher sensitivity. The defect candidates covered by the mask portion or separated by the mask are corrected in outline by a second localized defect detection operation, i.e. a second defect detection without a mask pattern. Thus, a correct defect profile, i.e. a defect profile without a mask, can be provided, which is advantageous for defect type classification. Correct defect contours, such as defect detection without mask patterns, allow determination of true defect areas and true defect sizes.

Fig. 2 illustrates a side view of an apparatus for imaging a portion of a substrate, particularly for imaging with a scanning charged particle beam microscope for large area displays, such as for display manufacturing, according to embodiments described herein. The apparatus 100 includes a vacuum chamber 120. The apparatus 100 further includes a substrate support 110 on which a substrate 160 may be supported. The apparatus 100 comprises a first imaging charged particle beam microscope 130. In addition, the apparatus may include a second imaging charged particle beam microscope 140. In the example shown in fig. 2, a first imaging charged particle beam microscope 130 and a second imaging charged particle beam microscope 140 are arranged above the substrate support 110.

As further shown in fig. 2, the substrate support 110 extends along an x-direction 150. In the drawing plane of fig. 2, the x-direction 150 is the left-right direction. The substrate 160 is disposed on the substrate support 110. The substrate support 110 is movable in the x-direction 150 to displace the substrate 160 in the vacuum chamber 120 relative to the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140. Thus, the area of the substrate 160 may be located under the first imaging charged particle beam microscope 130 or under the second imaging charged particle beam microscope 140 for DR measurements. The region may include structures for DR measurement contained in or on a coating on the substrate. The substrate support 110 may also be movable in the y-direction (not shown) such that the substrate 160 may be movable in the y-direction, as described below. By appropriately displacing the substrate support 110 holding the substrate 160 within the vacuum chamber 120, a portion along the entire range of the substrate 160 may be measured within the vacuum chamber 120.

The first imaging charged particle beam microscope 130 is a distance 135 from the second imaging charged particle beam microscope 140 along the x-direction 150. In the embodiment shown in fig. 2, the distance 135 is the distance between the center of the first imaging charged particle beam microscope 130 and the center of the second imaging charged particle beam microscope 140. In particular, the distance 135 is a distance along the x-direction 150 between a first optical axis 131 defined by the first imaging charged particle beam microscope and a second optical axis 141 defined by the second imaging charged particle beam microscope 140. The first optical axis 131 and the second optical axis 141 extend along the z-direction 151. The first optical axis 131 may for example be defined by the objective lens of the first imaging charged particle beam microscope 130. Similarly, the second optical axis 141 may be defined, for example, by an objective lens of the second imaging charged particle beam microscope 140.

As further shown in fig. 2, the vacuum chamber 120 has an interior width 121 along the x-direction 150. The inner width 121 may be the distance that is obtained when passing through the vacuum chamber 120 in the x-direction from the left hand wall 123 of the vacuum chamber 120 to the right hand wall 122 of the vacuum chamber 120. One aspect of the present disclosure relates to the size of the device 100 relative to, for example, the x-direction 150. According to an embodiment, the distance 135 along the x-direction 150 between the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140 may be at least 30cm, such as at least 40cm. According to other embodiments, which may be combined with other embodiments described herein, the internal width 121 of the vacuum chamber 120 may be in the range of 250% to 450% of the distance 135 between the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140. Further details, aspects and features are described below with respect to fig. 2 and 3.

Accordingly, embodiments described herein may provide an apparatus for imaging a portion of a substrate, particularly a large area substrate, using two imaging charged particle beam microscopes remote from each other in a vacuum chamber. The substrate is processed as a whole in a vacuum chamber. In particular, embodiments described herein do not require damaging the substrate or etching the surface of the substrate. Thus, a high resolution image for defect inspection measurement can be provided.

As provided by some embodiments described herein, an advantage of having a reduced size vacuum chamber is that one or more vibrations of the vacuum chamber may be reduced because the vibration level increases depending on the size of the vacuum chamber. Therefore, the vibration amplitude of the substrate can also be advantageously reduced.

Exemplary first and second imaging charged particle beam microscopes have a distance in the first direction in the range of 30% to 70% of the first receiving area size of the substrate receiving area. More particularly, the distance along the first direction may be in the range of 40% to 60% of the first receiving area size, for example about 50% of the first receiving area size. For example, referring to the embodiment shown in fig. 2, the distance along the first direction may refer to the distance 135 between the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140. In the exemplary embodiment shown in fig. 2, distance 135 is about 50% of the width 220 of substrate receiving area 210.

The substrate support may be movable in the vacuum chamber relative to the first imaging charged particle beam microscope and/or relative to the second imaging charged particle beam microscope. According to an embodiment, which may be combined with other embodiments described herein, the second imaging charged particle beam microscope is at a distance of at least 30cm, more particularly at least 40cm, from the first imaging charged particle beam microscope, such as about 50% of the size of the first receiving area. An advantage of having a minimum distance between the first and second imaging charged particle beam microscopes (i.e. a distance that is greater than the distance at which only two imaging charged particle beam microscopes, e.g. two SEMS, are repeated next to each other to obtain redundancy) is that the distance travelled by the substrate inspected by the apparatus is reduced. This allows the size of the vacuum chamber to be reduced, so that vibrations of the vacuum chamber can also be advantageously reduced.

According to some embodiments, which may be combined with other embodiments described herein, an apparatus for imaging a portion of a large area substrate may further include a controller 180. The controller 180 may be connected (see reference numeral 182) to the substrate support 110, and in particular, a displacement unit of the substrate support. Further, the controller 180 may be connected to a scanning deflector assembly 184 of an imaging charged particle beam microscope, such as the first imaging charged particle beam microscope 130 and the imaging second charged particle beam microscope 140.

The controller 180 includes a central processing unit (central processing unit; CPU), a memory, and, for example, a support circuit. To facilitate control of the apparatus for inspecting large area substrates, the CPU may be one of any form of general purpose computer processor that may be used in an industrial environment to control various chambers and sub-processors. The memory is coupled to the CPU. The memory or computer readable medium may be one or more readily available memory devices such as random access memory, read only memory, floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits may be coupled to the CPU for supporting the processor in a conventional manner. These circuits include caches, power supplies, clock circuits, input/output circuitry and related subsystems, etc. The inspection process instructions are typically stored in memory as software routines (commonly referred to as recipes). The software routines may also be stored and/or executed by a second CPU (not shown) located remotely from the hardware controlled by the CPU. The software routines when executed by the CPU transform a general-purpose computer into a special-purpose computer (controller) that controls device operation, such as for controlling substrate support positioning and charged particle beam scanning during an imaging process. Although the methods and/or processes of the present disclosure are discussed as being implemented as software routines, some of the method steps disclosed therein may be performed in hardware as well as by a software controller. As such, the invention may be implemented in software executing on a computer system and may be implemented in hardware as an application specific integrated circuit or other type of hardware implementation, or in a combination of software and hardware.

According to embodiments of the present disclosure, and as exemplarily described with reference to fig. 1A-1C, 5, and 6A-6E, a controller may perform or execute a method for performing defect inspection measurements on a substrate, for example, for display manufacturing.

According to one embodiment, an apparatus for imaging a portion of a substrate is provided. The apparatus includes a vacuum chamber and a substrate support disposed in the vacuum chamber. According to some embodiments, which may be combined with other embodiments described herein, the substrate support may optionally provide at least 1.2m ² Is provided. The apparatus further includes a first imaging charged particle beam microscope and a controller having a processor and a memory storing instructions that when executed by the processor cause the apparatus to perform a method according to any of the embodiments of the present disclosure.

According to one embodiment, a method for performing defect inspection measurements on a substrate is provided. The method includes generating a defect image of a portion of the substrate including the defect, and generating a reference image corresponding to the defect image. A mask pattern is determined based on the reference image. The defect image and the reference image are compared in a region outside the mask pattern to detect a defect. According to some embodiments, which may be combined with other embodiments described herein, defects are re-detected without a mask pattern. For example, a defect profile of the defect may be determined. According to yet another alternative implementation, a class image view of the defect may be generated.

Fig. 3 illustrates a side view of another apparatus for imaging a portion of a substrate according to embodiments described herein. The apparatus 100 includes a vacuum chamber 120. The apparatus 100 further includes a substrate support 110 on which a substrate 160 may be supported. The apparatus 100 comprises a first imaging charged particle beam microscope 130. In contrast to fig. 2, fig. 3 illustrates a single imaging charged particle beam microscope disposed above the substrate support 110. Even though this may result in reduced imaging capabilities, e.g., reduced resolution, the resulting resolution may be sufficient for some DR measurements. Furthermore, for semiconductor wafer applications where the defect size of the defect to be detected is small compared to acceptable manufacturing tolerances, an apparatus for imaging a portion of a substrate with a single imaging charged particle beam microscope may be provided. Similar to fig. 2, the apparatus shown in fig. 3 may include a controller and a deflection assembly. The controller may be connected to the substrate support, and in particular the displacement unit of the substrate support. In addition, the controller may be connected to a deflection assembly of the imaging charged particle beam microscope.

Defect inspection measurements are typically provided on various areas of a substrate, such as a wafer in semiconductor fabrication or a large area glass substrate such as used in display fabrication. Thus, a statistical analysis of defect inspection of the structure can be performed over the entire substrate area and over multiple processed substrates. For small substrates, such as wafers, this can be accomplished with methods known in the semiconductor industry with sufficient throughput. In the semiconductor industry, tool-to-tool matching of measurement capabilities is provided. For electron beam inspection (EBR) of display substrates, two imaging charged particle beam microscopes (see fig. 2) in one device can be matched with respect to each other. This is related to relative position and measurement capability. A single column device (see fig. 3) can avoid column matching in one system while accepting reduced resolution. The multi-pillar device may advantageously include pillar matching and have increased resolution.

According to some embodiments, which may be combined with other embodiments described herein, a method of operating an apparatus for imaging of the present disclosure may include matching a first coordinate system on a large area substrate of a first imaging charged particle beam microscope with a second coordinate system on a large area substrate of a second imaging charged particle beam microscope.

Both options, i.e., single-column and multi-column methods, allow for the improved DR measurement process described herein, where adequate detection sensitivity is provided, as well as adequate throughput, particularly also on large area substrates. According to embodiments of the present disclosure, DR measurements as described herein may be provided in various regions of a large area substrate. For example, two or more regions, such as 5 regions to 100 regions, may be distributed over the substrate.

An imaging charged particle beam microscope as used herein may be adapted to generate a low energy charged particle beam having a landing energy of 2keV or less, in particular 1keV or less. In contrast to the high energy beam, the low energy beam does not affect or damage the display backplane structure during defect inspection measurements. According to other embodiments, which may be combined with other embodiments described herein, the charged particle energy, e.g. electron energy, may be increased to 5keV or higher, such as 10keV or higher, between the particle beam source and the substrate. Accelerating the charged particles within the column reduces interactions between the charged particles, reduces aberrations of the electro-optic components, and thus improves resolution of the imaging scanning charged particle beam microscope.

According to yet another embodiment, which may be combined with other embodiments described herein, the term "substrate" as used herein includes non-flexible substrates, e.g. glass substrates or glass plates, as well as flexible substrates, such as webs or foils. The substrate may be a coated substrate, wherein one or more thin layers of material are coated or deposited on the substrate, for example by a physical vapor deposition (physical vapor deposition, PVD) process or a chemical vapor deposition process (chemical vapor deposition process, CVD). Substrates used in display manufacturing typically comprise an insulating material, such as glass. Thus, in contrast to semiconductor wafer SEM, the apparatus for imaging portions of a large area substrate does not allow biasing of the substrate. According to embodiments described herein, which may be combined with other embodiments described herein, the substrate is grounded. The substrate cannot be biased to a potential that affects landing energy or other electro-optic aspects of the scanning electron beam microscope. This is another example of the difference between EBR systems for large area substrates and SEM inspection of semiconductor wafers. This may further lead to electrostatic discharge problems (electrostatic discharge, ESD) when substrate processing is performed on the substrate support. Thus, it can be seen that the wafer inspection scheme may not be readily applicable to DR measurements of substrates for display manufacturing.

According to other embodiments, which may be combined with other embodiments described herein, defect inspection measurements for large area displays used in display manufacturing may further distinguish semiconductor wafers DR based on scanning techniques. In general, analog scanning techniques and digital scanning techniques can be distinguished. The analog scanning technique may include an analog sawtooth signal provided to the scanning deflector assembly at a predetermined frequency. The saw tooth signal may be combined with a continuous or quasi-continuous substrate movement to the substrate scanning area. Digital scanning techniques provide discrete values for x-and y-positioning of a charged particle beam on a substrate, and individual pixels of a scanned image are addressed pixel-by-pixel, i.e., digitally, by coordinate values. Due to the scan speed and reduced complexity, analog scan techniques ("flight phase") may be considered preferable for semiconductor wafer SEM inspection, but it has no benefit for DR measurement of large area substrates. Due to the size of the substrate, the area to be scanned is digitally scanned, i.e. by providing a list of targets for the desired beam positions. That is, the image is scanned using a digital scanning technique, i.e., a digital scanner. Such scanning processes provide better throughput and accuracy due to the size of the substrate.

According to some embodiments, which may be combined with other embodiments described herein, the field of view of an imaging charged particle beam microscope for use in a method and apparatus according to the present disclosure may have a size of 500 μm or less and/or a size of 5 μm or more. The resolution of the image may be about 100nm or less, such as 20nm or less, for example 10nm or less.

The method for defect inspection of an image may receive a list of defects or defect candidates from a controller or interface of a display manufacturing plant. For example, pixels of a display may be tested using a display test method. Pixel defects, line defects, drive defects, or other defects may be tested with an electron beam test system and an optical test system or other measurements (such as electrical measurements). Thus, the defective pixels may be provided for defect inspection measurements and/or may be provided to a device for defect inspection measurements. The area of defective pixels is an image for providing a defective image. The regions, e.g., corresponding regions of adjacent pixels, are measured to provide a reference image. DR measurements can be used to evaluate defect inspection for defects from previous metrology tools. Because of the size of the substrate used for display manufacturing and the resulting manufacturing process challenges, the locations for performing defect inspection measurements on large area substrates as described with respect to embodiments of the present disclosure may be distributed over the large area substrate. For example, the display may have 500 ten thousand or more pixels, such as about 800 ten thousand pixels. A large display may include a higher number of pixels. For each pixel, at least an electrode for red, an electrode for green, and an electrode for blue are provided. Thus, defects that are considered critical to the manufacturing process may occur over a very large area. As described above, embodiments of the present disclosure include providing DR measurements based on a first operation using a mask pattern and a subsequent second operation without a mask pattern. DR measurements are provided at the structure of the defect image using a reference image.

According to some embodiments, which may be combined with other embodiments described herein, the defect image is generated at a defective pixel on the substrate, and the reference image is generated at a pixel adjacent to the defective pixel, in particular at a pixel adjacent to the defective pixel. Additionally or alternativelyAlternatively, the defect inspection measurements may be repeated over one or more areas of the substrate, the areas being distributed over at least 1.2m ² And (3) upper part.

According to some embodiments, which may be combined with other embodiments described herein, the substrate described herein relates to a large area substrate, in particular for the display market. According to some embodiments, a large area substrate or corresponding substrate support may have a thickness of at least 1m ² Such as at least 1.375m ² Is of a size of (a) and (b). The size may be from about 1.375m ² (1100 mm. Times.1250 mm-Gen 5) to about 9m ² More particularly from about 2m ² Up to about 9m ² Or even up to 12m ² . The substrate or substrate receiving area for which structures, apparatus and methods according to embodiments described herein are provided may be a large area substrate as described herein. For example, the large area substrate or carrier may be a substrate corresponding to about 1.375m ² GEN 5 of the substrate (1.1mX1.25m), corresponding to about 4.39m ² GEN 7.5 of substrate (1.95 m×2.25 m), corresponding to about 5.7m ² GEN 8.5 of the substrate (2.2 m×2.5 m), or even corresponding to about 9m ² GEN 10 of the substrate (2.88 m.times.3130m). Even larger generations such as GEN 11 and GEN 12 and corresponding substrate areas may be similarly implemented. It must be considered that the substrate size generation provides a fixed industry standard even though the size of the GEN 5 substrate may vary slightly from one display manufacturer to another. Embodiments of the apparatus for testing may, for example, have a GEN 5 substrate support or GEN 5 substrate receiving area such that GEN 5 substrates of many display manufacturers may be supported by the support. The same applies to other substrate size generations.

Fig. 4 illustrates an imaging charged particle beam microscope, i.e., a charged particle beam apparatus 500, such as a first imaging charged particle beam microscope and/or a second imaging charged particle beam microscope as described herein. The charged particle beam device 500 comprises an electron beam column 420 providing, for example, a first chamber 421, a second chamber 422 and a third chamber 423. The first chamber, which may also be referred to as a gun chamber, includes an electron beam source 430 having an emitter 31 and a suppressor 432.

The emitter 431 is connected to a power supply 531 for providing an electrical potential to the emitter. The potential supplied to the emitter may be such that the electron beam is accelerated to an energy of, for example, 20keV or higher. Thus, the emitter may be biased to a potential of-1 kV voltage to provide a landing energy of 1keV to the grounded substrate. The upper electrode 562 is set at a higher potential for directing electrons through the column at a higher energy.

Using the apparatus shown in fig. 5, the electron beam source 430 may generate an electron beam (not shown). The beam may be aligned with a beam limiting aperture 550 that is sized to shape the beam, i.e., block a portion of the beam. Thereafter, the beam may pass through a beam splitter 580, which separates the primary electron beam from the signal electron beam, i.e. from the signal electrons. The primary electron beam may be focused on the substrate 460 through an objective lens. The substrate 460 is positioned at a substrate location on the substrate support 410. Upon impact of the electron beam onto the substrate 460, signal electrons, such as secondary and/or backscattered electrons or x-rays, are released from the substrate 460, which may be detected by the detector 598.

In the exemplary embodiment shown in fig. 4, a focusing lens 520 and a beam shaping or beam limiting aperture 550 are provided. A two stage deflection system 540 is disposed between the focusing lens and a beam limiting aperture 550 (e.g., a beam shaping aperture) for directing the beam at the aperture. Electrons can be accelerated by the extractor or anode to a voltage in the column. The extractor may be provided, for example, by the upper electrode of the focusing lens 520 or by another electrode (not shown).

As shown in fig. 4, the objective lens has a magnetic lens component 561 having

pole pieces

464 and 463 and having a coil 462 that focuses the primary electron beam on a substrate 460. The substrate 460 may be positioned on the substrate support 410. The objective lens shown in fig. 4 comprises an upper pole piece 463, a lower pole piece 464 and a coil 462, forming a magnetic lens component 461 of the objective lens. Further, the upper electrode 562 and the lower electrode 530 form an electrostatic lens component of the objective lens.

Further, in the embodiment shown in fig. 4, a scanning deflector assembly 570 is provided. The scan deflector assembly 570 (see also scan deflector assembly 184 in fig. 2) may be, for example, magnetic, but is preferably an electrostatic scan deflector assembly configured for high pixel rates. The scan deflector assembly 570 may be a single stage assembly, as shown in fig. 4. Alternatively, a two-stage or even three-stage deflector assembly may be provided. The respective tables are disposed at different positions along the optical axis 2.

The lower electrode 530 is connected to a voltage source (not shown). The embodiment shown in fig. 4 illustrates the lower electrode 530 below the lower pole piece 464. The lower electrode is a deceleration electrode of the immersion lens part (i.e. the retarding field lens part) of the objective lens, typically at a potential for providing a charged particle landing energy of 2keV or less, e.g. 500V or 1keV, on the substrate.

Beam splitter 580 is adapted to split primary electrons and signal electrons. The beam splitter may be a Wien filter and/or may be at least one magnetic deflector such that the signal electrons are offset from the optical axis 402. The signal electrons are then directed by a beam bender 591 (e.g., a hemispherical beam bender) and a lens 595 to a detector 598. Other elements like filter 596 may be provided. According to a further modification, the detector may be a segmented detector configured to detect signal electrons in dependence of the starting angle at the sample.

The first and second imaging charged particle beam microscopes may be charged particle beam devices of the imaging charged particle beam microscope type, such as the charged particle beam device 500 shown in fig. 4.

Fig. 5 illustrates a flow chart illustrating a method for performing defect inspection measurements on a substrate. At operation 510, a reference image is generated. As described with reference to fig. 1A to 1C, a mask pattern is generated from a reference image at operation 511. Further, a defect image is generated at operation 512. An image of a portion of the substrate including a defect (e.g., a known defect) is generated. For example, a defect image may be provided at a substrate portion where defects of pixels have been previously reported by a metrology process.

As shown in fig. 6A, a comparison image 30, for example, a differential image, is generated. The comparison image is covered by a mask pattern 32. Defect selection is provided outside the area of the mask pattern 32 within the comparison image.

According to some embodiments, which may be combined with other embodiments described herein, the comparison image may be a differential image or another comparison image. Intensity signals for the reference image and the defect image may be calculated and/or determined for each pixel of the image. For example, the reference image and the defect image may be aligned relative to each other to align pixels of the image. The difference in intensity signals may be provided by an absolute value of the difference in intensity signals. Alternatively, the relevant structure (edges) of the reference image may be extracted from the display layout design data (CAD data). The reference structure may be extracted from the same unit cell location from which the defect image was acquired. Additionally or alternatively, reference images may be stored. Therefore, acquiring the reference image for each defect position can be omitted. References to layout CAD data and/or stored reference images may increase throughput of defect inspection. No new reference image is acquired for each DR measurement.

Fig. 6B illustrates an enlarged view of fig. 6A. As shown in fig. 6B, defects 22 outside the mask pattern 32 may be selected. The defect icon illustrates the deviation between the reference image and the defect image in the region outside the mask pattern 32, i.e., the bright spot in the comparative image. Accordingly, at operation 513, a defect may be selected based on the masked comparison image. As shown in fig. 6C, the defect may be re-detected in the region 62 of the comparison image 30. Additionally or alternatively, defects may be re-detected in the defect image in region 62. According to operation 514, local re-detection of the defect may be provided without a mask pattern.

Fig. 6D illustrates a defect image. According to some embodiments, which may be combined with other embodiments described herein, a partial image 60 of the area of the selected defect may be provided. For example, the defect may be re-detected within the comparison image (i.e., a portion of the comparison image). Additionally or alternatively, the contour 64 may be determined in the defect image 60. For automatic defect classification (automatic defect classification, ADC), it is beneficial to see defects in a larger FOV. The relationship with the adjacent pattern structure may be evaluated (see fig. 6D). A higher zoom image illustrating more defect detail may be provided as shown, for example, in fig. 6E. The partial image may be a digital zoom of the defect image. Additionally or alternatively, another defect image may be generated at a different resolution than the defect image, for example measured with an imaging charged particle microscope. In particular, the further defect image may have a higher resolution than the defect image, i.e. the initial defect image.

As shown in fig. 6D, without the mask pattern 32, the defect profile 64 may be provided by local re-detection of defects (see, e.g., operation 515). This may be provided in the comparison image 30 or the defect image 60. For classification of images, a class image view 80 may be provided (see fig. 6E). According to some embodiments, which may be combined with other embodiments, the image-like view may have an increased resolution, for example by rescanning the desired FOV with an imaging charged particle beam microscope. The class image view may be based in particular on the determined defect contour. Depending on the size of the defect contour, the class image or class image view may icon an area comprising the defect and having a predetermined ratio of the size compared to the size of the defect contour.

Due to the use of a two-step method of defect selection and re-detection, in particular local re-detection, on the masked comparison image, a higher sensitivity, improved edge suppression and/or size defect profile detection may be provided without a mask pattern.

While the foregoing is directed to embodiments, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A method for performing defect inspection measurements on a substrate, comprising the steps of:

generating a defect image of the substrate portion including the defect;

generating a reference image corresponding to the defect image;

determining a mask pattern based on the reference image; and

the defect image and the reference image in a region outside the mask pattern are compared to detect the defect.

2. The method of claim 1, further comprising the step of:

the defects are re-detected without the mask pattern, in particular with a reduced search area and/or with a field of view around the detected defect location.

3. The method of claim 2, further comprising:

and determining a defect profile of the defect.

4. A method as in claim 3, further comprising:

and generating a class image view of the defect.

5. The method of any of claims 2 to 4, wherein the defect is re-detected with the defect image, or wherein the defect is re-detected with another defect image generated at a different resolution than the defect image.

6. The method of any of claims 1 to 5, wherein the defect image is generated at a defective pixel on the substrate, and wherein the reference image is generated at a pixel adjacent to the defective pixel, in particular the reference image is generated at a pixel adjacent to the defective pixel.

7. The method of any one of claims 1 to 6, wherein the defect image and the reference image are generated by a scanning electron beam.

8. The method of any one of claims 1 to 7, wherein the defect image is measured by an intensity signal of signal electrons of a charged particle beam device.

9. The method of any one of claims 1 to 8, wherein the field of view is measured with a digital scanner.

10. The method of claim 9, wherein the field of view has a size of 200 μιη or less and/or a size of 5 μιη or more.

11. The method of any one of claims 1 to 10, further comprising the step of:

repeating the defect inspection measurement over one or more additional areas of the substrate, the areas being distributed over at least 1.2m ² And (3) upper part.

12. An apparatus for imaging a portion of a substrate, the apparatus comprising:

a vacuum chamber;

a substrate support disposed in the vacuum chamber;

a first imaging charged particle beam microscope; and

a controller, comprising: a processor and a memory storing instructions that when executed by the processor cause the apparatus to perform the method of any one of claims 1 to 11.

13. The apparatus for imaging a portion of a substrate of claim 12, wherein the substrate receiving area has a first receiving area dimension along a first direction, the apparatus further comprising:

a second imaging charged particle beam microscope, wherein the first imaging charged particle beam microscope and the second imaging charged particle beam microscope have a distance along the first direction that is 30% to 70% of the size of the first receiving area.

14. The apparatus for imaging a portion of a substrate of claim 13, wherein the second imaging charged particle beam microscope is at a distance of at least 30cm from the first imaging charged particle beam microscope along the first direction.

15. A method of operating the apparatus of any of claims 12 to 13, comprising the steps of:

a first coordinate system on the substrate of the first imaging charged particle beam microscope is matched to a second coordinate system on the substrate of the second imaging charged particle beam microscope.