CN114895524B

CN114895524B - Defect detection method and system for EUV (extreme ultraviolet) photomask body

Info

Publication number: CN114895524B
Application number: CN202210493423.6A
Authority: CN
Inventors: 季明华; 任新平; 黄早红
Original assignee: Shanghai Chuanxin Semiconductor Co ltd
Current assignee: Shanghai Chuanxin Semiconductor Co ltd
Priority date: 2022-04-25
Filing date: 2022-04-25
Publication date: 2023-03-24
Anticipated expiration: 2042-04-25
Also published as: CN114895524A

Abstract

The invention provides a defect detection method and a defect detection system for an EUV (extreme ultraviolet) photomask body, which can scan at least one to-be-detected position point of the EUV photomask body to be detected by adopting extreme ultraviolet lasers with different wavelengths on the premise of not damaging the EUV photomask body to be detected (comprising an EUV mask blank or an EUV photomask with a corresponding pattern), so as to obtain corresponding reflectivity, and the defect information of the corresponding to-be-detected position point, including the information in the transverse distribution range and the deep level, is obtained by analyzing the reflectivity.

Description

Defect detection method and system for EUV (extreme ultraviolet) photomask body

Technical Field

The invention relates to the technical field of photoetching, in particular to a method and a system for detecting defects of an EUV (extreme ultraviolet) photomask body.

Background

Extreme Ultraviolet (EUV) lithography is an advanced lithography technique in the integrated circuit manufacturing industry that applies EUV laser wavelengths (13.5 nm). Among them, EUV photomasks (photo masks) are important components in the photolithography process. The EUV lithography process generally includes coating a photoresist layer such as a photoresist on a wafer surface, drying the photoresist layer, exposing a pattern on an EUV photomask to the photoresist layer with an EUV laser (wavelength of 1nm to 100nm, for example, 13.5 nm) using an exposure apparatus, developing the exposed photoresist layer with a developer, etching the wafer using the developed photoresist layer pattern as a mask, and finally completing transfer of the pattern on the EUV photomask to the wafer.

During the manufacturing of EUV photo mask bodies comprising EUV mask blanks or EUV photo-reticles with corresponding patterns, the presence of defects is inevitable and these defects may affect the final EUV lithography result. Therefore, defect detection of EUV mask blanks or EUV reticles has also been one of the issues of intense research in the art.

Disclosure of Invention

The invention aims to provide a defect detection method and a defect detection system for an EUV photomask body, which can detect defects on the EUV photomask body comprising an EUV mask blank or an EUV photomask with a corresponding pattern.

To achieve the above object, the present invention provides a defect inspection method of an EUV photomask body, comprising:

scanning at least one position point to be detected of an EUV (extreme ultraviolet) photomask body to be detected by adopting extreme ultraviolet lasers with different wavelengths to obtain the reflectivity of the extreme ultraviolet laser with each wavelength at the position point to be detected, wherein the EUV photomask body to be detected comprises an EUV mask blank or an EUV photomask with corresponding patterns;

and analyzing the reflectivity of the position point to be detected to obtain the defect information of the position point to be detected.

Optionally, extreme ultraviolet lasers with different wavelengths are respectively used for traversing each position point to be detected of the EUV photo mask body to be detected, so as to obtain the reflectivity of the EUV photo mask body to be detected at the non-defective position point, and the reflectivity of the position point to be detected except the non-defective position point is used as a reference, so as to analyze the reflectivity of the position point to be detected except the non-defective position point, so as to determine the defect information of the position point to be detected except the non-defective position point.

Optionally, the method for detecting defects of an EUV photomask body further comprises: collecting and analyzing related data of a historical EUV photomask to obtain the reflectivity of a defect-free position point of the EUV photomask body to be detected corresponding to different wavelengths;

and analyzing the reflectivity at the position to be detected by taking the reflectivity at the defect-free position as a reference standard so as to determine the defect information of the position to be detected.

Optionally, the method for detecting defects of an EUV photomask body further comprises: and drawing the reflectivity at the defect-free position points at different wavelengths into a reflectivity-wavelength curve.

Optionally, the method for detecting defects of an EUV photomask body further comprises: and respectively traversing each position point to be detected of the EUV photo mask body to be detected by adopting extreme ultraviolet lasers with different wavelengths, and obtaining a distribution graph of the reflectivity of each wavelength on the EUV photo mask body to be detected.

Optionally, the method for detecting defects of an EUV photomask body further comprises: and comparing the reflectivity of a plurality of adjacent positions to be measured at the same wavelength to determine the information of the corresponding defects including the transverse distribution range and/or the vertical thickness variation.

Optionally, the incident angles of the euv lasers with different wavelengths are all the same, and the incident angle is 0 to 15 °.

Optionally, the incident angle of the extreme ultraviolet laser with different wavelengths is set to be the same as the preset exposure light incident angle of the EUV photomask body to be measured.

Optionally, the adjustment range of the wavelength of the EUV laser for scanning each position point to be measured of the EUV photomask body to be measured can at least include a wavelength range in which a period is formed by the maximum reflectivity and the minimum reflectivity.

Optionally, the wavelength of the extreme ultraviolet laser for scanning each position point to be detected of the EUV photomask body to be detected is adjusted within a range of λ/2-2 λ, where λ is the extreme ultraviolet laser wavelength at which the reflective film stack layer of the EUV photomask body to be detected can generate the maximum reflectivity, or λ is the wavelength of exposure light preset by the EUV photomask body to be detected.

Based on the same inventive concept, the invention also provides a defect detection system of the EUV photo mask body, which comprises:

the base station is used for placing the EUV photomask, moving the position of the EUV photomask body to be tested and adjusting the inclination angle of the EUV photomask body to be tested, wherein the EUV photomask body to be tested comprises an EUV mask blank or an EUV photomask with a corresponding pattern;

the extreme ultraviolet laser source is used for providing extreme ultraviolet laser with different wavelengths to corresponding to position points to be detected of the EUV photomask body to be detected;

the detector is used for collecting the extreme ultraviolet laser reflected from the position point to be detected so as to obtain the reflectivity of the corresponding position point to be detected to the extreme ultraviolet laser with each wavelength, and analyzing the reflectivity of the position point to be detected so as to obtain the defect information of the position point to be detected;

a controller for controlling and coordinating the movement and operation of the base station, the EUV laser source, and the detector.

Optionally, the adjusting range of the wavelength of the EUV laser provided by the EUV laser source to the corresponding point to be measured on the EUV photomask body to be measured at least includes a wavelength range which produces a period consisting of the maximum reflectivity and the minimum reflectivity.

Compared with the prior art, the technical scheme of the invention has at least one of the following effects:

1. on the premise of not damaging the EUV photo mask body to be detected (including an EUV mask blank or an EUV photo mask with a corresponding pattern), at least one position point to be detected of the EUV photo mask body to be detected is scanned by adopting extreme ultraviolet lasers with different wavelengths to obtain corresponding reflectivity, and defect information of the corresponding position point to be detected, including information in a transverse distribution range and a deep layer, is obtained through analysis of the reflectivity.

2. The reflectivity of a plurality of adjacent to-be-measured position points of the EUV photomask body to be measured (including an EUV mask blank or an EUV photomask with a corresponding pattern) is analyzed, and a distribution diagram of the reflectivity of each wavelength on the EUV photomask body to be measured can be obtained, so that the transverse distribution range of defects can be visually observed from the distribution diagram, meanwhile, the difference of the reflectivity of the plurality of adjacent to-be-measured position points of the EUV photomask body to be measured under the same wavelength is compared, and the vertical thickness difference of the to-be-measured position points can be obtained.

3. By taking the reflectivity-wavelength curve of the defect-free position point of the EUV photo mask body to be detected (including an EUV mask blank or an EUV photo mask with a corresponding pattern) as a reference line, observing the change of the maximum value and the minimum value of the reflectivity of other position points to be detected of the EUV photo mask body to be detected relative to the reference line, the information of the defect distribution of the corresponding position points to be detected of the EUV photo mask body to be detected can be obtained, wherein the information comprises transverse distribution, vertical thickness change (namely information in a deep layer) and the like.

4. The defect detection system of the EUV photo mask body has an extreme ultraviolet laser source and wavelength tuning capability, and can be used for automatically realizing defect detection of the EUV photo mask body (including an EUV mask blank or an EUV photo mask with a corresponding pattern).

Drawings

FIG. 1 is a schematic cross-sectional view of a conventional EUV photomask.

Fig. 2 to 5 are schematic diagrams of defect structures in existing EUV photo mask bodies (including EUV mask blanks or EUV photo masks having corresponding patterns).

FIG. 6 is a flowchart of a method for defect detection of an EUV photomask body (including an EUV mask blank or an EUV photomask having a corresponding pattern) according to an embodiment of the present invention.

Fig. 7 is a schematic diagram of λ =13.5nm selected in a defect detection method for an EUV photomask body (including an EUV mask blank or an EUV photomask blank having a corresponding pattern) according to an embodiment of the present invention.

FIG. 8 is a schematic diagram of a defect detection system for an EUV photomask body (including an EUV mask blank or an EUV photomask blank having a corresponding pattern) according to an embodiment of the present invention.

FIG. 9 is a schematic illumination of a location point in a method of defect inspection of an EUV photomask body (including an EUV mask blank or an EUV photomask having a corresponding pattern) according to an embodiment of the present invention.

FIG. 10 is a schematic diagram of a reflectivity profile in a method of defect inspection of an EUV photomask body (including an EUV mask blank or an EUV photomask blank having a corresponding pattern) according to an embodiment of the present invention.

FIG. 11 is a schematic illustration of the reflection at different points on an EUV photomask body (including an EUV mask blank or an EUV photomask blank having a corresponding pattern) according to an embodiment of the present invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention. It is to be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity to indicate like elements throughout.

It will be understood that when an element or layer is referred to as being "on" \8230 "(" the other element or layer), it can be directly on, adjacent to, connected to, or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on" … or "directly on" another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, sections and/or processes, these elements, components, regions, layers, sections and/or processes should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, portion and/or process from another element, component, region, layer, portion and/or process. Thus, a first element, component, region, layer, section and/or process discussed below could be termed a second element, component, region, layer, section and/or process without departing from the teachings of the present invention.

Spatial relational terms such as "under 82303030," "under 823030; below," "under 823030; above," "over," "on top surface," "on bottom surface," "front surface," "back surface," and the like may be used herein for convenience of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, then elements or features described as "under" or "beneath" or "under" or "on the bottom surface or" on the back surface of "other elements or features would then be oriented" on "or" top "or" right "the other elements or features. Thus, the exemplary terms "under 8230," "at 8230303030, under" and "at 8230, back" may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

As described in the background, EUV photomasks are important components of EUV lithography (EUVL) systems.

Referring to fig. 1, a method for manufacturing a known EUV photomask includes the following steps:

1. and (4) manufacturing a mask blank. Specifically, the following operations are performed in order:

1.1, providing a substrate 100, and carrying out wet cleaning on the substrate 100;

1.2, alternately depositing a molybdenum (Mo) film and a silicon (Si) film on the substrate 100 by any suitable Deposition method, such as sputtering, chemical Vapor Deposition (CVD), plasma Enhanced CVD (PECVD), atomic Layer Deposition (ALD), plasma Enhanced ALD (PEALD), ion Beam Deposition (IBD), etc., to form the reflective film stack Layer 101;

1.3, depositing a covering layer 102 on the top surface of the reflective film stack layer 101 by any suitable deposition method such as sputtering, CVD, PECVD, ALD, PEALD, etc.;

1.4, depositing an absorption layer 103 on the top surface of the capping layer 102 by any suitable deposition method such as sputtering, CVD, PECVD, ALD, PEALD, IBD, etc., wherein the absorption layer 103 may be a single layer structure or a multi-layer stacked structure, for example, a chromium (Cr) based or tantalum (Ta) based material;

1.5, depositing a hard mask layer (not shown) on the top surface of the absorption layer 103 by any suitable deposition method such as CVD, PECVD, ALD, PEALD, etc.;

1.6, a backside conductive layer 105 is deposited on the bottom surface of the substrate 100 by any suitable deposition method, such as CVD, PECVD, ALD, PEALD, IBD, etc.

2. Fabrication of the first pattern 103 a. Specifically, the following operations are performed in order:

2.1, coating and baking a photoresist (PR, not shown), and exposing and developing the photoresist by laser, electron beam or ion beam to form a patterned photoresist layer;

2.2, taking the patterned photoresist layer as a mask, and etching the hard mask layer by plasma, wherein the etching is stopped on the top surface of the absorption layer 103;

2.3 oxygen (O) ₂ ) Dry ashing (dry ashing) the photoresist layer with plasma, followed by applying various organic acids, inorganic sulfuric acid, and H at high temperature ₂ O ₂ Wet stripping (wet striping) of the photoresist followed by an isopropyl alcohol (IPA) rinse and CO ₂ Washing to remove the photoresist layer;

2.4, dry plasma etching the absorber layer 103, stopping the etching on the top surface of the cap layer 102, forming a desired first pattern 103a in the absorber layer 103, the first pattern 103a being a pattern of circuits and/or devices required for integrated circuit fabrication.

3. Fabrication of the second pattern 104. Specifically, the following operations are performed in order:

3.1, coating and baking a photoresist (PR, not shown), and exposing and developing the photoresist by laser, electron beam or ion beam to form a patterned photoresist layer;

3.2, using the patterned photoresist layer as a mask, wet or dry plasma etching the absorption layer 103 and the reflective film stack layer 102 at the periphery of the first pattern 103a, stopping the etching on the top surface of the substrate 100, and forming a second pattern 104, wherein the second pattern 104 is a frame pattern required by the integrated circuit manufacturing.

3.3 oxygen (O) ₂ ) Dry ashing (dry ashing) the photoresist layer with plasma, followed by applying various organic acids, inorganic sulfuric acid, and H at high temperature ₂ O ₂ Wet stripping (wet stripping) photoresistLayer, followed by isopropyl alcohol (IPA) rinse and CO ₂ And washing to remove the photoresist layer.

4. Cleaning, inspecting and transporting.

Defects are introduced by the surface condition of the substrate 100, the deposition process, the etching process, the photoresist layer removing process, and the like during the manufacture of the EUV photomask body (including the EUV mask blank or the EUV reticle), and therefore, the existence of defects is inevitable during the manufacture of the EUV photomask body (including the EUV mask blank or the EUV reticle), and the defects affect the final result of the EUV photomask for EUV lithography.

The inventors have found that the defects common to EUV photo mask bodies (including EUV mask blanks or EUV photo-masks having corresponding patterns) are specifically the following: a) The defects with larger size (> 10nm size) existing on the surface of the substrate 100, such as the pits (pits) 100a in fig. 2 or the bumps (bumps) 100b in fig. 3 or scratches (not shown), are formed on the surface of the substrate 100 by Chemical Mechanical Polishing (CMP) and cleaning processes, and are induced in the layers of the reflective film stack 101 deposited directly upward from the substrate (as shown in fig. 2), or the defects may grow in size (as shown in fig. 3) and/or shift in position laterally (as shown in fig. 4) due to stress, thickness variation, etc. during the upward induction process, and finally generate the corresponding induced defects 101a in the layers of the deposited reflective film stack 101. b) Particle (or contaminant, etc.) defects temporarily generated during deposition of each layer of the reflective film stack 101 and defects 101b induced by the particle defects in the layer of the reflective film stack 101 above them are shown in fig. 5.

All these defects affect the final performance of EUV lithography.

In the prior art, defects are usually detected by using methods such as an AFM (Atomic Force Microscope), an SEM (Scanning Electron Microscope), a TEM (Transmission Electron Microscope), and the like, but these defect detection methods can only detect defects on the surface of the EUV photomask, or can only detect defects in a few layers of the EUV photomask, and/or can only detect internal defects of the EUV photomask in a manner of damaging the EUV photomask, and cannot detect and locate defects in a deep layer of the EUV photomask.

Based on this, the invention provides a defect detection method and system for an EUV photomask body (including an EUV mask blank or an EUV photomask with a corresponding pattern), which can scan at least one position point of the EUV photomask body to be detected (including the EUV mask blank or the EUV photomask with the corresponding pattern) by using extreme ultraviolet laser with different wavelengths (for example, the wavelength is in the range of λ/2-2 λ, λ =13.5 nm) to obtain the reflectivity of the ultraviolet laser at the wavelength of the position point to be detected, and analyze the reflectivity to obtain the defect information of the position point to be detected.

Further, the reflectivity of a plurality of adjacent to-be-measured position points of the to-be-measured EUV photomask body (including an EUV mask blank or an EUV photomask with a corresponding pattern) is analyzed, so that a distribution diagram of the reflectivity of each wavelength on the to-be-measured EUV photomask body can be obtained, a transverse distribution range of defects (the defects are distributed in a point shape or a sheet shape) can be visually observed from the distribution diagram, and meanwhile, the difference of the reflectivity of the plurality of adjacent to-be-measured position points of the to-be-measured EUV photomask body under the same wavelength is compared, and the vertical thickness difference of the to-be-measured position points can be obtained.

Further, by taking the reflectivity-wavelength curve of the defect-free position point of the EUV photomask body to be measured (including the EUV mask blank or the EUV photomask with the corresponding pattern) as a reference line, the change of the maximum value and the minimum value of the reflectivity of each other position point to be measured of the EUV photomask body to be measured relative to the reference line is observed, so that the information of the defect distribution of the corresponding position point to be measured of the EUV photomask body to be measured, including transverse distribution, vertical thickness change and the like, can be obtained.

Further, the corresponding position points to be detected of the EUV photomask are scanned by the wavelengths at the wave crests and the wave troughs of the reflectivity-wavelength curve of the defect-free position points, namely the maximum reflectivity and the minimum reflectivity of the EUV photomask body to be detected (including an EUV mask blank or the EUV photomask with the corresponding pattern) are mainly analyzed, and the defect detection efficiency of the EUV photomask body is greatly improved.

The method for detecting defects of an EUV photomask body (including an EUV mask blank or an EUV photomask blank having a corresponding pattern) according to the present invention is described in detail below with reference to fig. 1, 6 to 11 and specific embodiments.

An embodiment of the present invention provides a defect inspection method for an EUV photomask body, which may be used to inspect a defect of the EUV photomask body to be inspected, where the EUV photomask body to be inspected may be an EUV mask blank that has not undergone the manufacturing of the first pattern and the second pattern, or may be an EUV photomask blank having a corresponding pattern (i.e., the first pattern and/or the second pattern). Therefore, according to the structure of the EUV mask blank to be tested, the defect inspection method of this embodiment may be performed after depositing the reflective film stack layer, the capping layer, or the absorber layer of the EUV mask blank, or may be performed after photolithography and etching the EUV mask blank to form the desired circuit pattern and the frame pattern. That is to say, in this embodiment, the EUV photomask blank to be tested, which needs to be subjected to defect detection, may be an EUV mask blank, or an EUV photomask blank having a corresponding pattern after performing processes such as photolithography and etching, and in any case, the EUV photomask blank to be tested at least has the substrate 100 and the reflective film stack layer 101 formed on the substrate 100.

The substrate 100 is preferably a material with low thermal expansion and high thermal conductivity, such as low thermal expansion glass or quartz, and may specifically be quartz glass, microcrystalline glass (Zerodur), ultra low expansion coefficient quartz glass (ULE, also called zero expansion glass), and the like. In some embodiments the low thermal expansion glass is capable of transmitting light at visible wavelengths, a portion of the infrared wavelengths near the visible spectrum (near infrared), and a portion of the ultraviolet wavelengths. Further, the substrate 100 may absorb extreme ultraviolet laser wavelengths as well as deep ultraviolet wavelengths near extreme ultraviolet. The reflective film stack layer 101 is mainly formed by alternately laminating a first reflective film (not shown) and a second reflective film (not shown) on the front surface of the substrate 100. The number of layers of the first reflective film is, for example, 30 to 80, and preferably 40 to 50, and the film thickness is, for example, 3nm to 4nm. The first and second reflective films may be any suitable material that is capable of high reflectivity (e.g., greater than 70%) for euv laser light of a particular wavelength (e.g., 13.5 nm). For example, the material of the first reflective film is silicon (Si), and the material of the second reflective film is molybdenum (Mo). For another example, the first reflective film is made of Mo, and the second reflective film is made of beryllium (Be).

It should be understood that when the EUV photomask body to be tested further comprises the capping layer 102, the absorbing layer 103 and the backside conductive layer 105, the capping layer 102, the absorbing layer 103 are sequentially covered on the reflective film stack layer 101, and the backside conductive layer 105 is covered on the backside of the substrate 100.

The capping layer 102 is used to protect the reflective film stack layer 102 from being damaged by subsequent processes, and may be made of ruthenium (Ru), ruthenium alloy (such as RuB, ruSi or RuNb), or ruthenium oxide (such as RuO) ₂ Or RuNbO), which may have a single-layer film structure or a laminated structure of multiple films, and the thickness of the cover layer 202 is, for example, 2nm to 4nm. In other embodiments of the present invention, when the top layer of the reflective film stack 101 is made of silicon, the fabrication of the capping layer 102 may be omitted, or a silicon film (i.e., the first reflective film on the top layer) is deposited as the capping layer 102 when the reflective film stack 101 is formed.

The absorption layer 103 may have a single-layer film structure or a composite structure in which multiple layers of films are stacked, and the material thereof includes at least one of cobalt (Co), tellurium (Te), hafnium (Hf), nickel (Ni), tantalum (Ta), chromium (Cr), a tantalum-based material, a chromium-based material, and the like. The total thickness of the absorption layer 203 is, for example, 50nm to 75nm, and when the absorption layer 103 is a composite structure in which a plurality of films are stacked, the thickness of a single film therein is, for example, 3nm to 6nm.

The material of the back conductive layer 105 may include at least one conductive material of chromium, a chromium-based material (e.g., chromium nitride CrN or chromium oxynitride CrON), tantalum, or a tantalum-based material (e.g., tantalum boride TaB, tantalum oxide TaO, tantalum nitride TaN, tantalum boride TaBO, or tantalum nitride TaBN, etc.). The thickness of the back conductive layer 105 is, for example, 60nm to 75nm.

Referring to fig. 6, the method for detecting defects of an EUV photomask body (including an EUV mask blank or an EUV photomask blank having a corresponding pattern) of the present embodiment includes:

s1, scanning at least one to-be-detected position point of an EUV (extreme ultraviolet) photomask body to be detected by adopting extreme ultraviolet lasers with different wavelengths to obtain the reflectivity of the extreme ultraviolet laser with each wavelength at the to-be-detected position point, wherein the EUV photomask body to be detected is an EUV mask blank or an EUV photomask with corresponding patterns;

s2, analyzing the reflectivity of the position point to be detected to obtain the defect information of the position point to be detected.

In this embodiment, in step S1, different wavelengths of the EUV laser light selected for scanning each position point to be measured of the EUV photomask blank or the EUV photomask having a corresponding pattern) of the EUV photomask blank to be measured are generated based on the wavelength of the exposure light source of the exposure system required by the EUV photomask blank to be measured, and the incident angles of the EUV laser light with different wavelengths are the same and are set to be the same as the incident angle of the exposure light emitted by the exposure light source of the exposure system required by the EUV photomask blank to be measured, so that more film layers of the EUV photomask blank to be measured can be penetrated through, and defects affecting the EUV lithography result can be better focused, thereby facilitating the subsequent analysis of the reflectivity at each position point to be measured in step S2 to obtain the corresponding defect information on the EUV photomask blank to be measured relatively directly, more obviously, and more efficiently. The exposure light source of the exposure system required by the EUV photomask body to be measured specifically is as follows: the EUV photomask body to be tested is applied to an EUV photoetching process in product manufacturing, and the EUV photomask body to be tested is used as a mask to expose a corresponding film layer by using an exposure light source adopted by an exposure system.

In this embodiment, in step S1, the adjustment range of the wavelength of the EUV laser for scanning each position point to be measured of the EUV photomask body to be measured at least includes a wavelength range in which a period is formed by the maximum reflectance and the minimum reflectance. Specifically, a reflectivity-wavelength curve corresponding to a defect-free position point a (0, 0) of the EUV photomask body to be detected at different wavelengths may be obtained in advance by collecting and analyzing related data of a historical EUV photomask, and a wavelength range at least including a period consisting of a maximum reflectivity and a minimum reflectivity is obtained from the reflectivity-wavelength curve as a wavelength range of the EUV laser used for detecting defects of the EUV photomask body to be detected. Therefore, reflectivity information including the maximum reflectivity and the minimum reflectivity of each position point to be detected can be obtained in the wavelength adjusting range, and the defect detection efficiency and accuracy are further improved.

Preferably, in this embodiment, a wavelength range of the extreme ultraviolet laser used for performing defect detection on the EUV photomask body to be detected is λ/2 to 2 λ, where λ is an extreme ultraviolet laser wavelength at which the reflective film stack layer of the EUV photomask body to be detected can generate a maximum reflectance, or λ is a wavelength of exposure light preset by the EUV photomask body to be detected.

In an example of this embodiment, λ is a wavelength of exposure light preset by the EUV photomask body to be measured. Taking the most advanced 13.5nm euv lithography technology at present as an example, the wavelength of the exposure light source adopted by the 13.5nm euv lithography technology is 13.5nm, which can be used for chip manufacturing at 7nm, 5nm and 3nm, so λ =13.5nm in this example. After extreme ultraviolet lasers with different wavelengths in the wavelength range of lambda/2-2 lambda scan each position point to be measured of the EUV photo mask body to be measured, corresponding reflectivity analysis is used in the subsequent step S2, not only can defect information on the surface of the EUV photo mask body to be measured be obtained, but also defect information in the deep layer of the EUV photo mask body to be measured can be obtained. This is different from the situation that the existing detection means can only detect the surface defect information of the EUV photo-mask. This is because:

referring to fig. 7, for an EUV photomask blank (including an EUV mask blank or an EUV photomask blank having a corresponding pattern), when 1 first reflective film and 1 second reflective film sequentially stacked in the reflective film stack 101 are defined as a dual-film structure, after an EUV laser with a wavelength of 13.5nm is perpendicularly or approximately perpendicularly incident on the EUV photomask blank, at least about 31 dual-film structures can be penetrated by the EUV photomask blank, and the EUV photomask blank is bragg for the EUV laser with the wavelength of 13.5nmThe reflectivity is at least 60%, such as 70%, 80% or 85%. And 193nm or 199nm deep ultraviolet laser (DUV) can only penetrate to about 3 double-film structures after being vertically or approximately vertically incident to the EUV photomask body; after the ultraviolet laser with the wavelength of 266nm is vertically or approximately vertically incident to the EUV photomask body, only about 2 double-film structures can be penetrated; after the 488nm laser is vertically or approximately vertically incident to the EUV photomask body, the laser can penetrate through about 13 double-film structures at most; electron beam (e) ^- ) After perpendicular or approximately perpendicular incidence on the EUV photo mask body, only about 1-2 double-film structures can be penetrated. It is apparent that 193nm or 199nm deep ultraviolet light, 266nm ultraviolet light, 488nm laser and electron beam (e) are selected ^- ) When the conventional light or electron beam for detecting defects of a mask plate or a mask blank is used, only defects on the surface of the EUV photomask or defects in a few top double-film structures can be detected, and the extreme ultraviolet laser with the wavelength of 13.5nm can effectively detect defects in most or even all double-film structures of the EUV photomask.

Similarly, extreme ultraviolet laser light of other wavelengths in the wavelength range of 13.5nm/2 to 2 × 13.5nm can penetrate and detect a very large number of double-film structures of the EUV photomask body, and thus defects in most or all of the double-film structures of the EUV photomask body can be effectively detected.

In step S1, when scanning each position point to be measured of the EUV photomask body to be measured (including an EUV mask blank or an EUV photomask blank having a corresponding pattern) with different wavelengths, specifically, the wavelength may be continuously adjusted from λ/2 to 2 λ according to a sequence from small to large, or continuously adjusted from 2 λ to λ/2 according to a sequence from large to small, or at least two of the wavelength (λ/2, λ) corresponding to each peak and the wavelength (0.66 λ and 2 λ) corresponding to each valley in the reflectance-wavelength curve of the defect-free position point may be selected according to a sequence from small to large, or from large to small, to perform extreme ultraviolet laser wavelength scanning on each position point to be measured B (X, Y) of the EUV photomask body to be measured. Thereby, the reflectivity of each position point to be measured of the EUV photomask body under different wavelengths is obtained, i.e. the corresponding reflectivity of each position point to be measured B (X, Y), for example at least one of the maximum reflectivity, the minimum reflectivity and the reflectivity-wavelength curve is obtained.

Furthermore, in step S1, referring to fig. 8, the EUV photomask body 110 to be tested may be placed on the base 111, and the base 111 may fix the position of the EUV photomask body 110 to be tested and adjust the inclination angle of the surface of the EUV photomask body 110 to be tested, and maintain a constant incident angle θ between the surface of the EUV photomask body 110 to be tested and the optical axis a of the incident EUV laser beam 203 emitted by the EUV laser source 201, where θ is 0 to 15 °, and preferably not more than 6 °. In order to improve the measurement effect, the spot size of the incident euv laser beam 203 emitted by the euv laser source 201 may be adjusted to a minimum by the focus adjuster 202. The detector 205 is fixed in position to detect the reflected euv laser beam 204 and obtain a corresponding reflectivity. The EUV light source 201 is preferably a point light source or a line light source, and is excited to emit an incident EUV laser beam 203 with a tunable wavelength, and the tunable wavelength range of the incident EUV laser beam 203 emitted by the EUV light source 201 can be generated based on the wavelength of the exposure light source required by the EUV photomask body 110 to be measured.

In a preferred embodiment, in step S1, the base 111 may be controlled by the controller 200 to translate the EUV photomask body 110 to be measured, or the EUV laser source 201 may be controlled by the controller 200 to translate into the EUV laser beam 203, so as to perform step-wise scanning on the entire surface of the EUV photomask body 110 to be measured, while maintaining a constant incident angle θ between the normal of the EUV photomask body 110 to be measured and the optical axis of the incident EUV laser beam 203, so as to complete the purpose of traversing all position points to be measured of EUV reticles with different wavelengths of EUV laser.

Specifically, in step S1, please refer to fig. 8 and 9, a position point to be measured may be first located, and the wavelength of the incident EUV laser beam 203 emitted by the EUV laser source 201 is continuously adjusted or selectively adjusted according to the order from small to large or from large to small, specifically, the adjustment range of the wavelength of the incident EUV laser beam 203 emitted by the EUV laser source 201 is λ/2-2 λ, or the wavelengths of the incident EUV laser beam 203 emitted by the EUV laser source 201 are λ/2, 0.66 λ, and 2 λ in sequence, so as to complete scanning and reflectivity measurement of the position point to be measured, and then step to a next position point to be measured, and repeat the above operations, that is, the wavelength of the EUV laser is adjusted again according to the order from small to large, so as to complete scanning and reflectivity measurement of the next position point to be measured, and so on, and EUV operations are repeated until all position points to be measured of the mask body to be measured are traversed. Wherein λ is, for example, 13.5nm, and in other embodiments of the present invention λ may be selected from any one of values from 1nm to 100 nm.

Referring to fig. 10 and 11, different positions (for example, three positions a, B1, and B2 in fig. 11) on an EUV photomask body to be tested (including an EUV mask blank or an EUV photomask having a corresponding pattern) reflect different EUV lasers having the same wavelength according to different defect conditions, so that even though the EUV lasers having the same wavelength are incident at the same light intensity and incident angle, the obtained reflectivity is not completely the same at different positions of the EUV photomask body to be tested, and the more serious the defect (for example, the more the double-layer film structure involved in the defect) is, the more serious the drift degree (including the horizontal axis and the vertical axis) in the reflectivity-wavelength curve relative to the defect-free position is.

In step S2, the reflectivity of each position point to be measured of the EUV photomask body to be measured (including an EUV mask blank or an EUV photomask blank with a corresponding pattern) is analyzed to obtain defect information of each position point to be measured of the EUV photomask body to be measured, where the defect information includes: there are defects, lateral extent of defects, depth and vertical thickness of defects (i.e., information within the depth level), and so on.

Optionally, in this embodiment, in step S2, the means for analyzing the reflectivity of each position-to-be-measured point of the EUV photomask blank to be measured (including the EUV mask blank or the EUV photomask blank having the corresponding pattern) includes: distribution graphs (which can be two-dimensional plane graphs or three-dimensional solid graphs) of the reflectivity of different wavelengths (such as lambda/2, 0.66 lambda, 2 lambda and the like) on the EUV photo mask body to be measured are obtained, so that the defect distribution condition on the EUV photo mask body to be measured and the transverse distribution range (such as point distribution or sheet distribution) of each defect can be visually observed from the distribution graphs. Further, in these distribution maps, information of the vertical thickness, the depth position, and the like of the corresponding defect can be obtained by observing the corresponding reflectivity contour (maximum reflectivity contour and/or minimum reflectivity contour) at the same wavelength, or observing the degree of the corresponding reflectivity (maximum reflectivity or/and minimum reflectivity) deviation of each position point to be measured with respect to the position point without the defect. In other embodiments of the present invention, when the wavelengths used in step S1 have other wavelengths than λ/2, 0.66 λ, and 2 λ, the distribution map of the reflectivity at the other wavelengths on the EUV photomask body to be measured may be adaptively obtained in step S2 for analysis.

Optionally, in step S2, the means for analyzing the reflectivity of each measured position point of the EUV photomask body to be measured (including an EUV mask blank or an EUV photomask blank with a corresponding pattern) includes: and comparing the reflectivity of a plurality of adjacent positions to be measured under the same wavelength to determine information such as the transverse distribution range and/or the vertical thickness change of the corresponding defects.

Optionally, in step S2, the means for analyzing the reflectivity of each measured position point of the EUV photomask body to be measured (including an EUV mask blank or an EUV photomask blank with a corresponding pattern) includes: and (2) taking the reflectivity-wavelength curve at the defect-free position point obtained in the step (S1) as a reference line, and comparing the deviation degree of the reflectivity (or the reflectivity-wavelength curve) at each position to be detected relative to the reference line to obtain the defect information of each position to be detected.

It should be noted that, in the above embodiment, the reflectivity-wavelength curve corresponding to the defect-free position point of the EUV photomask body to be measured is obtained by analyzing the relevant data of the corresponding historical EUV photomask body (including the EUV mask blank or the EUV photomask with the corresponding pattern), but the technical solution of the present invention is not limited thereto. In other embodiments of the present invention, when the EUV laser with different wavelengths (for example, continuously changed in λ/2 λ -2 λ) is used to traverse each position point to be detected of the EUV photomask body to be measured (including the EUV mask blank or the EUV photomask blank with the corresponding pattern) in step S1, a defect-free position point or a position point approximately free of defects usually exists in the position points to be measured, and therefore, in step S2, a position point having the maximum reflectivity at λ/2 and λ (or in the vicinity) and the minimum reflectivity at 0.66 λ and 2 λ (or in the vicinity) may be used as a defect-free position point of the EUV photomask body to be measured, so as to obtain a reflectivity-wavelength curve at the defect-free position point of the EUV photomask body to be measured, and then the reflectivity at other position points to be measured may be analyzed by using the reflectivity-wavelength curve at the defect-free position point as a reference line, so as to determine defect information of the other position points to be measured.

It should be understood that, in order to shorten the defect detection time, at least two of the four different wavelengths λ/2, 0.66 λ, and 2 λ may be directly selected in step S1 to traverse each position-to-be-measured point of the EUV photomask body to be measured (including the EUV mask blank or the EUV photomask blank having the corresponding pattern), so that only the reflectivity at these wavelengths is analyzed in step S2, thereby improving the analysis efficiency. Since four different wavelengths λ/2, 0.66 λ, 2 λ correspond to the wavelengths involved in the maximum and minimum reflectivity of the EUV photo mask body to be measured.

In subsequent applications, according to the analysis result in step S2, a defective position to be detected of the EUV photomask body to be detected (including the EUV mask blank or the EUV photomask having a corresponding pattern) may be further longitudinally sliced or transversely sliced, so as to perform more detailed analysis on the defect of the position to be detected.

In summary, the method for detecting defects of an EUV photomask body (including an EUV mask blank or an EUV photomask blank with a corresponding pattern) of the present invention can scan at least one to-be-detected position of the EUV photomask body to be detected with extreme ultraviolet lasers with different wavelengths without damaging the EUV photomask body to be detected, so as to obtain corresponding reflectivities, and by analyzing the reflectivities, defect information of the corresponding to-be-detected position is obtained. Further, the reflectivity of a plurality of adjacent positions to be measured of the EUV photo mask body to be measured is analyzed, and a distribution diagram of the reflectivity of each wavelength on the EUV photo mask body to be measured can be obtained, so that the transverse distribution range of the defect can be visually observed from the distribution diagram, meanwhile, the difference of the reflectivity of the plurality of adjacent positions to be measured of the EUV photo mask body to be measured under the same wavelength is compared, and the vertical thickness difference of the positions to be measured can be obtained.

Based on the same inventive concept, referring to fig. 8, an embodiment of the present invention further provides a defect detection system for an EUV photomask blank (including an EUV mask blank or an EUV photomask blank with a corresponding pattern), which can be used to implement the defect detection method for an EUV photomask blank of the present invention, and the defect detection system includes: a base station 111, an extreme ultraviolet laser source 201, a focusing device 202, a detector 205, and a controller 200.

The base station 111 is used for placing the EUV photomask body 110 to be tested, moving the position of the EUV photomask body 110 to be tested, and adjusting the inclination angle of the EUV photomask 111 to keep the incident angle θ between the normal of the EUV photomask body 110 to be tested and the optical axis of the incident EUV laser beam 203 emitted by the EUV laser source 201 unchanged. The EUV photomask body 110 to be tested comprises an EUV mask blank or an EUV photomask blank with a corresponding pattern.

The extreme ultraviolet laser source 201 has a wavelength tuning capability, and can provide extreme ultraviolet laser (incident extreme ultraviolet laser beam 203) with different wavelengths to corresponding points to be measured of the EUV photomask body 110 to be measured, and the focusing device 202 is used for adjusting the focal length of the incident extreme ultraviolet laser beam 203 emitted by the extreme ultraviolet laser source 201 so as to change light spots on the surface of the EUV photomask body 110 to be measured, where the incident extreme ultraviolet laser beam 203 is incident. Wherein, the wavelength of the extreme ultraviolet laser light provided by the extreme ultraviolet laser light source 201 to the corresponding point to be measured of the EUV photo mask body 110 to be measured is between λ/2 and 2 λ, λ is 13.5nm for example. In order to improve the measurement effect, the spot size of the incident euv laser beam 203 emitted by the euv laser source 201 can be adjusted to a minimum by the focusing device 202.

The detector 205 is configured to collect the reflected EUV laser beam 204 reflected from a to-be-measured position of the to-be-measured EUV photomask body 110 (including an EUV mask blank or an EUV photomask with a corresponding pattern), so as to obtain a reflectivity of the to-be-measured position of the to-be-measured EUV photomask body 110 to each wavelength of the EUV laser, and analyze the reflectivity of the to-be-measured position to obtain defect information of the to-be-measured position. Further, the detecting device 205 can generate a distribution diagram of the reflectivity of each wavelength on the EUV photomask body to be detected, so that the lateral distribution range of the defect can be visually observed from the distribution diagram, and the detecting device can be used for comparing the reflectivity difference of a plurality of adjacent positions to be detected of the EUV photomask body to be detected at the same wavelength, and obtaining the vertical thickness difference of the positions to be detected.

The controller 200 is used to control and coordinate the movement and operation of the stage 111, the euv laser source 201, and the detector 205.

The method for using the defect detection system of the embodiment is as follows:

the EUV photomask body 110 to be tested (including an EUV mask blank or an EUV photomask blank with a corresponding pattern) is placed on a base 111, and the base 111 can fix the position of the EUV photomask body 110 to be tested and adjust the inclination angle of the surface of the EUV photomask body 110 to be tested, and the constant incident angle θ between the surface of the EUV photomask body 110 to be tested and the optical axis a of the incident EUV laser beam 203 emitted by the EUV laser source 201 is kept, wherein θ is 0 to 15 °, and is preferably not more than 6 °.

The controller 200 controls the base station 111 to translate the EUV photomask body 110 to be measured, or the controller 200 controls the EUV laser source 201 to translate into the EUV laser beam 203, so as to perform step-by-step scanning on the entire surface of the EUV photomask body 110 to be measured, and meanwhile, a constant incidence angle theta is kept between the normal of the EUV photomask body 110 to be measured and the optical axis of the incident EUV laser beam 203, so as to fulfill the purpose of traversing all position points to be measured of the EUV reticle by using the EUV lasers with different wavelengths. And in each position point to be measured of the EUV photomask body 110 to be measured, the wavelength of the incident extreme ultraviolet laser beam 203 emitted by the extreme ultraviolet laser source 201 is adjusted in the range of lambda/2 to 2 lambda in the order from small to large or in the order from large to small, so as to complete the scanning of each position point to be measured.

In summary, the defect detection system for the EUV photomask body of the present invention can automatically detect the defect of the EUV photomask body to be detected (including the EUV mask blank or the EUV photomask blank with the corresponding pattern), without damaging the structure of the EUV photomask body to be detected.

The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art according to the above disclosure are within the scope of the present invention.

Claims

1. A method for detecting defects of an EUV photomask body, comprising:

scanning at least one position point to be detected of an EUV (extreme ultraviolet) photomask body to be detected by adopting EUV lasers with the same incident angle and different wavelengths, wherein the wavelength adjusting range of the EUV lasers at least comprises a wavelength range which forms a period by generating maximum reflectivity and minimum reflectivity so as to obtain the reflectivity of the EUV lasers in the adjusting range at the position point to be detected, wherein the reflectivity of the EUV lasers at the position point to be detected comprises the maximum reflectivity and the minimum reflectivity, the EUV photomask body to be detected comprises an EUV mask blank or an EUV photomask with corresponding patterns, the EUV mask blank or the EUV photomask comprises a substrate and a reflecting stack film layer covered on the substrate, and the defects of the EUV photomask body comprise at least one of defects generated by defects existing on the surface of the substrate in the reflecting stack film layer, temporary particle defects generated in the depositing process of the reflecting stack film layer and defects generated by the particle defects in the reflecting stack film layer;

and analyzing the reflectivity including the maximum reflectivity and the minimum reflectivity at the position to be detected to obtain the defect information of the position to be detected.

2. The method for detecting defects of an EUV photomask body according to claim 1, wherein extreme ultraviolet lasers with different wavelengths are respectively used to traverse each position point to be detected of the EUV photomask body to be detected to obtain the reflectivity at a non-defective position point of the EUV photomask body to be detected, and the reflectivity at the position points to be detected other than the non-defective position point is analyzed with the reflectivity at the non-defective position point as a reference standard to determine the defect information of the position points to be detected other than the non-defective position point.

3. The method for defect inspection of an EUV photomask body of claim 1, further comprising: collecting and analyzing related data of a historical EUV photomask to obtain the reflectivity of a defect-free position point of the EUV photomask body to be detected corresponding to different wavelengths;

4. The method for defect inspection of an EUV photomask body of claim 2 or 3, further comprising: and drawing the reflectivity at the defect-free position points at different wavelengths into a reflectivity-wavelength curve.

5. The method for defect inspection of an EUV photomask body of claim 1, further comprising: and respectively traversing each position point to be detected of the EUV photo mask body to be detected by adopting extreme ultraviolet lasers with different wavelengths, and obtaining a distribution graph of the reflectivity of each wavelength on the EUV photo mask body to be detected.

6. The method for defect inspection of an EUV photomask body according to claim 1 or 5, further comprising: and comparing the reflectivity of a plurality of adjacent positions to be measured under the same wavelength to determine the information of the corresponding defects including the transverse distribution range and/or the vertical thickness variation.

7. The method for inspecting a defect of an EUV photo mask body according to claim 1, wherein the angle of incidence is in the range of 0 ° to 15 °.

8. The method for inspecting defects of an EUV photo mask body according to claim 1, wherein the incident angle of the EUV laser beam with different wavelengths is set to be the same as the preset incident angle of the exposure light of the EUV photo mask body to be inspected.

9. The method for detecting defects of an EUV photo mask body as claimed in any one of claims 1 to 3, 5 and 7 to 8, wherein the wavelength of the EUV laser used for scanning each point of the EUV photo mask body to be detected is adjusted to be in a range of λ/2 λ to 2 λ, where λ is the wavelength of the EUV light that the reflective film stack layer of the EUV photo mask body to be detected can generate the maximum reflectivity, or λ is the wavelength of the exposure light preset by the EUV photo mask body to be detected.

10. A system for defect inspection of an EUV photomask body, comprising:

the device comprises a base platform, a control platform and a control module, wherein the base platform is used for placing an EUV (extreme ultraviolet) photomask body to be tested, moving the position of the EUV photomask body to be tested and adjusting the inclination angle of the EUV photomask body to be tested, the EUV photomask body to be tested comprises an EUV mask blank or an EUV photomask with a corresponding pattern, the EUV mask blank or the EUV photomask comprises a substrate and a reflecting stack film layer covered on the substrate, and the defect of the EUV photomask body comprises at least one of a defect generated in the reflecting stack film layer by the defect existing on the surface of the substrate, a particle defect generated temporarily in the depositing process of the reflecting stack film layer and a defect generated in the reflecting stack film layer by the particle defect;

the extreme ultraviolet laser source is used for providing extreme ultraviolet laser with the same incident angle and different wavelengths to a corresponding position point to be detected of the EUV photomask body to be detected, and the wavelength adjusting range of the extreme ultraviolet laser at least can include a wavelength range which generates a period formed by the maximum reflectivity and the minimum reflectivity;

the detector is used for collecting the extreme ultraviolet laser reflected from the position point to be detected so as to obtain the reflectivity of the extreme ultraviolet laser in the adjusting range at the corresponding position point to be detected, wherein the reflectivity comprises the maximum reflectivity and the minimum reflectivity, and the reflectivity of the position point to be detected, which comprises the maximum reflectivity and the minimum reflectivity, is analyzed so as to obtain the defect information of the position point to be detected;