Pattern inspection apparatus and pattern inspection method for photomask

Abstract

To provide a pattern inspection apparatus and a pattern inspection method for a photomask to prevent detection (or recognition) of defects in an area corresponding to a pattern which is outside the manufacturing warranty of the photomask.SOLUTION: An apparatus for inspecting a pattern of a photomask retains mask pattern data which specify a mask pattern generated from a pattern outside the warranty of the photomask, acquires defect data by performing inspection of the photomask pattern, and removes the corresponding area of the mask pattern, based on the defect signals, from a defect recognition area where defects are to be recognized.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for inspecting a pattern on a photomask. [Background technology]

[0002] Photomasks are used in the manufacturing process of products such as electronic devices, including displays. For quality control and quality assurance of the photomasks, pattern inspection is performed in the photomask manufacturing process to inspect the patterns formed on the photomask. However, defects detected by pattern inspection may include not only true defects that have an impact on the product, such as defects or failures, but also false defects that have no impact on the product. An operator must check (defect review) whether the output results of the defect inspection by the pattern inspection device are true defects or false defects. In order to reduce the workload of the operator, methods have been proposed to reduce the detection of false defects by the pattern inspection device. Conventional methods for preventing the detection of false defects prevent the detection of false defects caused by a predetermined dimensional change (or shape change) from the designed pattern. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-198641 [Patent Document 2] JP 2000-258352 A Summary of the Invention [Problem to be solved by the invention]

[0004] Design patterns constituting the circuits of electronic devices may include design patterns that are not guaranteed to be formed in the photomask manufacturing process. For such design patterns that are not guaranteed to be formed in the manufacturing process, resolved and unresolved states are mixed in the manufactured photomask, and there are many defects that are detected by a pattern inspection device. However, if there is no effect on the performance or reliability of the device, correcting such a specific pattern that is not guaranteed in manufacturing increases the workload of the designer. If such a non-guaranteed pattern is permitted in order to reduce the workload of the designer, the number of defects detected in the pattern inspection process of the photomask manufacturing process will increase, and the workload of classifying the defects caused by the non-guaranteed pattern as false defects will increase.

[0005] In view of the above problems, an object of the present invention is to provide a photomask pattern inspection method and pattern inspection apparatus that prevent detection (or recognition) of defects in areas corresponding to patterns that are not guaranteed during the manufacture of the photomask. [Means for solving the problem]

[0006] The pattern inspection device according to the present invention comprises: An apparatus for inspecting a photomask for defects, comprising: mask pattern data of the photomask including a non-guaranteed design pattern; and defect data including the positions and shapes of defects obtained by pattern inspection of the photomask, The method is characterized in that an area corresponding to the non-guaranteed design pattern from the defect data is excluded from a defect recognition area that is recognized as a true defect.

[0007] By using such a pattern inspection apparatus, defects caused by patterns that are not covered by the manufacturing guarantee of the photomask can be tolerated, and not only the workload of defect review at the photomask manufacturing factory but also the workload of pattern design on the designer can be reduced.

[0008] In the above configuration, The area corresponding to the unwarranted design pattern may be removed from the defect recognition area or may be classified as a false defect distinct from the real defect.

[0009] By configuring such a pattern inspection apparatus, it becomes possible to utilize defect data from conventional pattern inspections.

[0010] In the above configuration, The area corresponding to the unguaranteed design pattern may be excluded from the area where the pattern inspection is performed.

[0011] By configuring the pattern inspection device in this manner, the burden on the pattern inspection device can be reduced.

[0012] A method for inspecting a photomask pattern according to the present invention comprises: a non-guaranteed pattern extraction step of extracting a non-guaranteed design pattern of the photomask based on a design pattern for forming a pattern of the photomask; a mask pattern generating step of generating a mask pattern including the unguaranteed design pattern; and performing a pattern inspection to detect true defects on the photomask, The method is characterized in that an area corresponding to the mask pattern is excluded from a defect recognition area that is recognized as a true defect.

[0013] By using such a photomask pattern inspection method, defects caused by patterns that are not covered by the manufacturing guarantee of the photomask can be tolerated, and not only the workload of defect review at the manufacturing factory but also the workload of pattern design on the designer can be reduced.

[0014] In the above configuration, The mask pattern may be generated by expanding the unguaranteed design pattern by a predetermined amount.

[0015] By using such a photomask pattern inspection method, the pattern can be generated accurately.

[0016] In the above configuration, The area corresponding to the mask pattern may be excluded from the defect recognition area by deleting defects in the area corresponding to the mask pattern from the defect data acquired in the pattern inspection process or classifying the defects as false defects.

[0017] By adopting such a photomask pattern inspection method, it becomes possible to utilize defect data from conventional pattern inspections.

[0018] In the above configuration, In the pattern inspection step, an area corresponding to the mask pattern may be excluded from an inspection area, thereby excluding the area corresponding to the mask pattern from the defect recognition area.

[0019] By adopting such a photomask pattern inspection method, the burden on the pattern inspection device can be reduced. Effect of the Invention

[0020] According to the present invention, it is possible to provide a photomask pattern inspection apparatus and a pattern inspection method that prevent detection (or recognition) of defects in areas corresponding to patterns outside the manufacturing guarantee of the photomask. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1(A) is a plan view showing a schematic example of a design pattern (design data) of a mask pattern, and FIGS. 1(B) and 1(C) are plan views showing schematic examples of patterns created on a photomask 100 using the design pattern shown in FIG. 1(A). [Diagram 2]Fig. 2 is a plan view for explaining a method for not detecting (or recognizing) defects in a non-guaranteed region. Fig. 2(A) is a plan view showing a schematic design pattern, Fig. 2(B) is a plan view showing a schematic non-guaranteed pattern below the resolution limit, Fig. 2(C) is a plan view showing a mask pattern to be excluded from inspection targets during pattern inspection, and Fig. 2(D) is an enlarged plan view showing the positional relationship between the non-guaranteed pattern and the mask pattern. [Diagram 3] Figure 3 is a plan view that illustrates the defect extraction process by a pattern inspection device. Figures 3(A) and 3(B) show plan views of a photomask 100 having a first pattern 2 and a second pattern 3 on a transparent substrate 1. Figure 3(C) is a plan view that illustrates the positional relationship between the defect detected by the pattern inspection device and the mask pattern area MA, and Figure 3(D) shows the defect recognized by the pattern inspection device. [Figure 4] Fig. 4 is a plan view for explaining an example of a method for determining the presence or absence of a non-guaranteed area for design pattern PT1 and design pattern PT2. Fig. 4(A) is a plan view showing an example of a determination pattern, Fig. 4(B) is a plan view showing an example of a guaranteed area, and Fig. 4(C) is a plan view showing examples of a guaranteed area and a non-guaranteed area. [Diagram 5] Figure 5 is a plan view showing non-limiting examples of various shapes of unguaranteed areas, where Figure 5(A) shows an example of an unguaranteed area having a sharp corner at its tip, Figure 5(B) shows an example of an unguaranteed area having a hole shape, and Figure 5(C) shows an example of an unguaranteed area having a free shape (arbitrary shape). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are not intended to limit the scope of the present invention. In addition, the same reference numerals are used for the same or similar components, and the description thereof may be omitted.

[0023] Furthermore, terms used in this specification that specify shapes, geometric conditions, and the extent thereof, such as "parallel," "orthogonal," and "same," as well as values ​​of length and angle, are not to be bound by strict meanings, but are to be interpreted to include a range within which similar functions can be expected.

[0024] (Embodiment 1) A method for inspecting the pattern of the photomask 100 will be described below with reference to the drawings. Fig. 1(A) is a plan view showing a schematic example of a design pattern (design data) for forming (patterning) a pattern (a pattern of various optical films) to be formed on a photomask 100. In Fig. 1(A), the area other than the first design pattern PT1 and the second design pattern PT2 is a blank (space) area corresponding to an area where the transparent substrate 1 is exposed. The dotted line in the figure indicates an area A where the distance between the first design pattern PT1 and the second design pattern PT2 is the minimum value d. The width d of the area A is equal to or less than the resolution limit D (d≦D) of the lithography process for forming a pattern on the photomask 100. Since the pattern width d of the area A is equal to or less than the resolution limit, the resolution is not guaranteed in the lithography process for manufacturing the photomask 100. Therefore, the pattern determined by the area A is not guaranteed to be opened because the patterning is not guaranteed in the manufacturing process. In this way, the pattern determined by the area where the patterning is not guaranteed in the manufacturing process is called a non-guaranteed pattern for convenience. Specifically, the non-guaranteed pattern determines an area where the manufacturing process is not guaranteed by having a size equal to or less than the resolution limit of the lithography process, which is the manufacturing process of the photomask. For example, the non-guaranteed pattern may occur in a part of the area between the two design pattern arrangements or may occur (or exist) in a part of the design pattern depending on the arrangement of the two design patterns as shown in the example of FIG. 1.

[0025] The design pattern is a pattern that constitutes a circuit diagram of a product (device) manufactured using the photomask 100, and is generally created by a designer using a CAD (design support tool). Hereinafter, the size of the design pattern corresponds to the photomask 100. For example, when a device is manufactured using a reduced projection exposure apparatus, the size of the design pattern is converted into a value that corresponds to the pattern size on the photomask 100, taking into account the reduction ratio as appropriate.

[0026] The design pattern is not limited to a design pattern for patterning an optical film formed on the transparent substrate 1, but may be a design pattern for patterning another optical film (e.g., a light-shielding film, etc.) formed on an underlying film, such as a semi-transmissive film or a phase shift film, formed on the transparent substrate 1. The pattern of the optical film on the photomask 100 patterned based on the design pattern and the configuration of the layer below the pattern are not limited. The same applies below.

[0027] 1(B) and (C) are plan views showing schematic examples of patterns in which a photoresist film formed on a photomask 100 is exposed by a drawing device or the like based on the design pattern shown in FIG. 1(A), and the exposed photoresist film is used to pattern an optical film on a transparent substrate 1. The object to be inspected by the pattern inspection apparatus is not limited to the pattern of the formed optical film, but may be a resist pattern.

[0028] As shown in Figures 1(B) and (C), a first pattern 2 corresponding to a first design pattern PT1 and a second pattern 3 corresponding to a second design pattern PT2 are formed on the photomask 100. As shown in FIG. 1B, an example is shown in which the photoresist film in the non-guaranteed area A is resolved and the optical film in the area B is opened. On the other hand, as shown in Fig. 1(C), an example is shown in which the photoresist film in the non-guaranteed area A is unresolved and the optical film in the area C is not opened. In this way, the pattern corresponding to the non-guaranteed area A may be resolved and a pattern may be formed, or may not be resolved and a pattern may not be formed. The material of the optical film of the first pattern 2 and the second pattern 3 is not limited, and may be a material having a light-blocking property, a material having semi-transparent property, or a material having a phase shift effect.

[0029] As described above, since the non-guaranteed area A may or may not be resolved, for example, in the case of a die-to-die comparison pattern inspection device that performs pattern inspection by comparing images of different dies, the positions and shapes of areas B and C are detected as pattern defects. Also, in a die-to-database comparison pattern inspection device that performs inspection based on a design pattern, the position and shape of area C are detected as a pattern defect.

[0030] However, even if it is a non-guaranteed area in the photomask manufacturing process, if a defect (see area C in FIG. 1(C)) corresponding to the non-guaranteed area A in an actual product (such as an electronic device) manufactured using the photomask does not affect the performance or quality of the actual product, the designer's workload of correcting (recreating) the design pattern can be reduced by allowing this defect (area C). In other words, the designer can request the manufacture of the photomask 100 without correcting the pattern in such a non-guaranteed area (non-guaranteed pattern). Since the designer is a circuit designer of the actual product, it is possible for the designer to determine whether or not the non-guaranteed area A affects the performance of the actual product.

[0031] Meanwhile, in a pattern inspection process included in the manufacturing process of the photomask 100, a pattern inspection device detects an area C corresponding to the non-guaranteed area A, and outputs it as a defect (hereinafter referred to as a detected defect). An operator at the manufacturing factory of the photomask 100 may determine (based on information from a circuit designer) that the detected defect in area C does not require correction, which increases the workload of classifying the detected defect as a false defect rather than a defect (a real defect). In this specification, a "pseudo defect" is defined as a defect detected by a pattern inspection device, but which is determined to have no effect on the performance, reliability, etc. of an actual product (such as an electronic device) and does not require any correction or other measures, as opposed to a "defect" (true defect) that has an adverse effect on the performance, reliability, etc. of a product.

[0032] Fig. 2 is a plan view for explaining a method for not detecting (or recognizing) defects in a non-guaranteed region. Fig. 2(A) is a plan view showing a typical design pattern, Fig. 2(B) is a plan view showing a typical non-guaranteed pattern which is a region below the resolution limit, Fig. 2(C) is a plan view showing a mask pattern which specifies a region to be excluded from a region to be inspected for defects (or a region to be recognized as a defect) during pattern inspection, and Fig. 2(D) is an enlarged plan view showing the positional relationship between the non-guaranteed pattern and the mask pattern. Therefore, the region other than that determined by the mask pattern becomes a region to be recognized as a defect during pattern inspection (hereinafter, may be referred to as a defect recognition region).

[0033] 2A shows a plan view of a design pattern having a first design pattern PT1 and a second design pattern PT2. Note that the design data specifying each design pattern constituting the circuit of the device includes data specifying the arrangement and shape of the first design pattern PT1 and the second design pattern PT2.

[0034] FIG. 2B is a plan view showing a non-guaranteed pattern PT3 (third design pattern PT3) corresponding to the non-guaranteed region. In the example shown in FIG. 2A, there is a portion where the distance between the first design pattern PT1 and the second design pattern PT2 is equal to or less than a predetermined value D (resolution limit of the lithography process for pattern formation). Therefore, as shown in FIG. 2B, a non-guaranteed pattern PT3 with a width d (d≦D) is extracted between the first design pattern PT1 and the second design pattern PT2. The extraction of the non-guaranteed pattern PT3 can be executed by a calculation processing device, and for example, a design rule check (DRC) of a CAD (design support tool) can be used to extract a region where the distance d between the first design pattern PT1 and the second design pattern PT2 is equal to or less than a predetermined value D, that is, the non-guaranteed pattern PT3. For example, the resolution limit value D can be specified as the minimum line width and the minimum space width as a design rule. The non-guaranteed patterns are not limited to the example shown in Fig. 2. They are extracted by a processor using CAD or the like based on data related to design patterns (including data on the layout between design patterns), but may also be extracted manually by the designer himself.

[0035] 2C shows a plan view of a mask pattern MT generated based on the extracted non-guaranteed pattern PT3. In each die on the photomask 100, an area (mask pattern area MA) designated by the mask pattern MT is excluded from the pattern inspection target (or the defect recognition area for recognizing defects). As shown in FIG. 2D, the mask pattern MT has a shape extended by a predetermined amount w (hereinafter, may be referred to as an extension width) with respect to the non-guaranteed pattern PT3. The extension width w can be determined, for example, in consideration of factors such as the misalignment between the design pattern and the pattern of the optical film. The misalignment between the design pattern and the pattern of the optical film can be obtained by optical simulation, actual measurement, etc. The extension width w may also be determined in consideration of the dimensional difference between the design pattern and the pattern of the optical film. Furthermore, when the pattern inspection is performed after the pattern formation of the optical film, the expansion width w may be determined further taking into consideration the pattern fluctuation due to the etching process. For example, the extension width w can be set, without limitation, to 1 to 5 pixels in the inspection image of the pattern inspection device.

[0036] The mask pattern MT can define an area (mask pattern area MA) corresponding to the mask pattern MT in the inspection image of the pattern inspection device. The mask pattern area MA and the mask pattern MT are substantially the same, but the mask pattern area MA is defined as an area of ​​the inspection image of the pattern inspection device.

[0037] In this way, data specifying the arrangement and the like of the mask pattern MT can be generated based on the extracted non-guaranteed pattern PT3 and the predetermined extension width w. The mask pattern MT can be automatically generated by a processing device, which may utilize a CAD tool. The processing device can read the design pattern data from a storage device in which the design pattern data indicating the arrangement, area, and the like of the design pattern is stored, extract the non-guaranteed pattern, perform arithmetic processing using the extension width w, and generate data (mask pattern data) specifying the arrangement, area (shape), and the like of the mask pattern.

[0038] The generated mask pattern data is transferred to a pattern inspection device and saved and held in a storage device of the pattern inspection device. The mask pattern data can be transferred using wired communication or wireless communication, or the mask pattern data may be transferred via a storage medium. The pattern inspection device can read mask pattern data from a storage device in which the mask pattern data is saved, inspect the pattern formed on the photomask 100, and output the inspection results. The arithmetic processing device may be built into the pattern inspection device, may be a part of the pattern inspection device, or may be provided separately from the pattern inspection device.

[0039] Hereinafter, a method of pattern inspection using the pattern inspection device will be described with reference to FIG. The pattern inspection device has a known pattern inspection mechanism, and can optically detect the pattern on the photomask 100 and detect the presence or absence of defects, the positions of the defects, and the like. The pattern to be inspected may be a resist pattern or a pattern made of an optical film.

[0040] Known pattern inspection devices include devices that use a method of comparing a design pattern, more specifically a reference image generated based on the design pattern, with a pattern (captured image) detected by the pattern inspection device to detect differences between the patterns (die to database comparison inspection), and devices that use a method of comparing patterns (captured images) of the same shape arranged in different locations on the photomask 100 (die to die comparison inspection), but any pattern inspection device may be used.

[0041] FIG. 3 is a plan view for explaining a schematic diagram of a defect extraction process by the pattern inspection device. 3(A) and 3(B) are plan views that diagrammatically show a photomask 100 having a first pattern 2 and a second pattern 3 on a transparent substrate 1. FIG. FIG. 3B shows an example of a defect (detected defect) detected by the pattern inspection device. FIG. 3C is a plan view showing a schematic diagram of the positional relationship between a defect detected by a pattern inspection device and a mask pattern area MA, and FIG. 3D shows a defect recognized by the pattern inspection device. In the pattern inspection device, an image corresponding to FIG. 3 is detected or captured, and the obtained image (inspection image) is subjected to arithmetic processing. Although the pattern shown in FIG. 3 is an example of a pattern of an optical film, it may be a resist pattern formed on the optical film.

[0042] In the example shown in FIG. 3(A), no defects are present, whereas in the example shown in FIG. 3(B), a first pattern defect Df1 is present in the first pattern 2, a second pattern defect Df2 is present in the second pattern 3, and a third pattern defect Df3 is present between the first pattern 2 and the second pattern 3. Here, the third pattern defect Df3 exists in an unguaranteed region (a region corresponding to region A in FIG. 1A) where the distance between the first pattern 2 and the second pattern 3 is equal to or smaller than the resolution limit D.

[0043] 3B, the pattern inspection device detects a first pattern defect Df1, a second pattern defect Df2, and a third pattern defect Df3. The pattern inspection device executes pattern inspection, obtains data on each defect (referred to as defect data or defect signal), such as information (data) on the position (coordinates) and the defective area (shape) on the photomask 100, and stores the data in a storage device of the pattern inspection device.

[0044] 3(C), the pattern inspection device collates the mask pattern data and recognizes that the data (position and area) of the third pattern defect Df3 is located within the mask pattern area MA. On the other hand, since the first pattern defect Df1 and the second pattern defect Df2 are not located within the mask pattern area MA, the pattern inspection device recognizes the first pattern defect Df1 and the second pattern defect Df2 as defects (true defects). The pattern inspection device can not recognize the defect (third pattern defect Df3) located in the mask pattern area MA as a defect (true defect) (not to be recognized as a defect) or delete (ignore) it. For example, the pattern inspection device recognizes the first pattern defect Df1 and the second pattern defect Df2 as defects (true defects) and does not recognize the third pattern defect Df3 as a defect, or the data of the third pattern defect Df3 is deleted from the defect signal.

[0045] In this way, the mask pattern area MA is configured or deleted so that the detected defect is not recognized as a defect (a true defect), and by being excluded from the area for recognizing defects, the third pattern defect Df3 in the non-guaranteed area is avoided from being recognized as a defect.

[0046] In the defect review work using a pattern inspection device, it is not necessary to review the mask pattern area MA, which is an area outside the guarantee, so that the workload of the worker can be reduced and the manufacturing period of the photomask 100 can be shortened.

[0047] The pattern inspection device may classify the third pattern defect Df3, which is a detected defect in the mask pattern area MA, as a pseudo defect (not a defect) and register it as a pseudo defect in the defect signal. The first pattern defect Df1 and the second pattern defect Df2 are maintained as registered (recognized) as defects in the defect signal.

[0048] If the mask pattern area MA is set unnecessarily large relative to the non-guaranteed area (for example, if the mask pattern area MA is set to a rectangular area with sides of several mm for a non-guaranteed area with a width of d=1 μm or less), it is possible to avoid (eliminate) recognition of defects in the non-guaranteed area, but it becomes impossible to detect defects (true defects) near the non-guaranteed area. As described above, by making the mask pattern area MA match the shape of the non-guaranteed area, it is possible to detect defects that need to be detected (the first pattern defect Df1 and the second pattern defect Df2) while avoiding recognition of defects in the non-guaranteed area.

[0049] In order to avoid recognizing defects in the mask pattern area MA, the pattern inspection device may, after completing inspection of all areas including the mask pattern area MA, perform a comparison between the detection data (inspection results) and the mask pattern area MA, thereby avoiding recognizing defects in the mask pattern area MA. In this case, the comparison between the mask pattern area MA and the defect signal (defect data) can be performed by the pattern inspection device itself (the arithmetic processing device in the pattern inspection device), but may also be performed by an inspection auxiliary device (or an arithmetic processing device) provided independently of the pattern inspection device. The inspection auxiliary device inputs the inspection data of the photomask 100 from the pattern inspection device, compares the inspection data with the information of the mask pattern area MA in the mask pattern database, and may not recognize (ignore) the detected defects located in the mask pattern area MA as defects, or may recognize (classify) them as pseudo defects, and store them as corrected detection data in a storage device of the inspection auxiliary device together with other true defects. The corrected detection data may be transmitted to the pattern inspection device and stored as a corrected defect signal (defect data) in a storage device of the pattern inspection device. An operator may then use a pattern inspection tool to perform a review of each defect based on the corrected defect signal.

[0050] Furthermore, in order to avoid recognizing defects in the mask pattern area MA, the pattern inspection device may exclude the mask pattern area MA from the inspection area (target area for pattern inspection) of the photomask 100. In this case, the pattern inspection device does not perform defect inspection of the mask pattern area MA in the photomask 100, so the third pattern defect Df3 is not detected, and the first pattern defect Df1 and the second pattern defect Df2 are detected. For example, the device is configured not to perform image processing for defect detection in the mask pattern area MA, or not to acquire image data of the mask pattern area MA. Since the mask pattern area MA is excluded from the area to be inspected for defects, it is also excluded from the area for recognizing defects, and for example, the third pattern defect Df3 in the non-guaranteed area is avoided from being recognized as a defect. By configuring the pattern inspection device so as not to perform pattern inspection in the mask pattern area MA, it is possible to reduce the burden of image processing and the like on the pattern inspection device.

[0051] 3(D), the third pattern defect Df3 is not recognized as a defect, and the pattern inspection device recognizes the first pattern defect Df1 and the second pattern defect Df2 as defects. The positions, areas, etc. of the recognized pattern defects are registered and stored in the pattern inspection device as defects. The operator does not need to inspect the third pattern defect Df3 in the defect review work, and the workload is reduced.

[0052] The method of configuring the mask pattern area MA so as not to recognize defects can be adopted regardless of the inspection method of the pattern inspection device. For example, this method can be adopted in any pattern inspection device that adopts die-to-database comparison inspection or die-to-die comparison inspection.

[0053] Hereinafter, with reference to FIG. 4, an example of a method for determining whether or not a design pattern or a part of a design pattern is an unguaranteed pattern will be described. In FIG. 4, the area of ​​the design pattern PT1 and the area of ​​the design pattern PT2 are areas having design pattern data for pattern formation, and the other areas are blank areas, for example areas where the transparent substrate 1 is exposed. Note that "having design pattern data" means having data that constitutes a design pattern such as design pattern PT1. For example, an area surrounded by a design pattern has design pattern data. Furthermore, the blank area is not limited to being an area where the transparent substrate 1 is exposed, but may be, for example, an area where an underlying film formed on the transparent substrate 1 is exposed, and the design pattern may be a pattern for patterning an upper layer film formed on the lower layer film.

[0054] As shown by the dotted line in FIG. 4A, a determination pattern CT having a square shape with a side length equal to the resolution limit D (for example, 1 μm) is prepared. The judgment pattern is not limited to a square, and may be, for example, a circular judgment pattern CT'. The judgment pattern may be appropriately set depending on the design pattern.

[0055] In the example shown in Figure 4 (B), the judgment pattern CT1 can be surrounded by the design pattern PT1, and the judgment pattern CT1 has all design pattern data. The judgment pattern CT1 having all design pattern data is determined not to be an unguaranteed area. Note that an area that is not an unguaranteed area is a resolvable area, and may be referred to as a guaranteed area below. Similarly, the judgment pattern CT2 is judged to be in the guaranteed area (not in the non-guaranteed area). Moreover, the inside of the judgment pattern CT3 is entirely blank, and in this case too, it is judged to be a guaranteed area.

[0056] In the example shown in FIG. 4C, a judgment pattern CT1 surrounded by a design pattern PT1 is in a guaranteed region, and the design pattern PT1 is determined to be in a guaranteed region. However, the determination pattern CT2 overlaps with the design pattern PT2 only partially, and has parts with design patterns and parts that are blank, and cannot be an area consisting of only design patterns or only blanks. In this case, the design pattern PT2 is determined to be a non-guaranteed area (not a resolvable area) based on the determination pattern CT2. Furthermore, the judgment pattern CT3, which overlaps with the space area between the design patterns PT1 and PT2, partially overlaps with the design patterns PT1 and PT2, and there are parts with design patterns and blank parts. The judgment pattern CT3 cannot be an area having only design pattern data or only a blank area. In this case, the judgment pattern CT3 judges that the space area between the design patterns PT1 and PT2 is a non-guaranteed area (not a resolvable area). A mask pattern area is set for each of these areas that are determined to be non-guaranteed areas. In the example shown in Fig. 4(C), the two mask pattern areas partially overlap, but the overlapping areas are also excluded from the area for defect recognition.

[0057] The unguaranteed area is not limited to a linear area as shown in Fig. 4, but has various shapes. Fig. 5 is a plan view showing non-limiting examples of the shapes of the unguaranteed area, in which Fig. 5(A) shows an example of an unguaranteed area having a sharp corner at the tip, Fig. 5(B) shows an example of an unguaranteed area having a hole shape, and Fig. 5(C) shows an example of an unguaranteed area having a free shape (arbitrary shape). In Fig. 5, (I) shows a design pattern, and (II) shows an extracted unguaranteed area.

[0058] In the example shown in (I) of FIG. 5(A), the insides of judgment patterns CT1 and CT2 are all blank areas, which are guaranteed areas. When judgment pattern CT2 is shifted in the X direction in the figure, as shown in judgment pattern CT3, its interior includes both an area having the design pattern data of design pattern PT1 and a blank area, and is determined to include a non-guaranteed area. Judgment pattern CT2 determines the boundary between the guaranteed area and the non-guaranteed area in the X direction. By moving judgment pattern CT, the boundary between the guaranteed area and the non-guaranteed area can be searched for and determined. The same applies below. In FIG. 5A, (II) shows the extracted non-guaranteed pattern PT3.

[0059] In the example shown in (I) in Figure 5 (B), the insides of judgment patterns CT1 and CT2 are all areas containing design pattern data and are judged to be guaranteed areas, but the inside of judgment pattern CT3 is a mixture of areas containing design pattern data and blank areas, and judgment pattern CT3 includes a non-guaranteed area. In FIG. 5B, (II) shows the extracted non-guaranteed pattern PT3.

[0060] In the example shown in (I) in Figure 5 (C), the insides of judgment patterns CT1 and CT2 are all blank and are judged to be guaranteed areas, but the inside of judgment pattern CT3 contains a mixture of areas having design pattern data and blank areas, and judgment pattern CT3 includes a non-guaranteed area. The judgment pattern CT1 and judgment pattern CT2 determine the boundary between the guaranteed area and the non-guaranteed area in the direction parallel to the X direction. In FIG. 5C, (II) shows the extracted non-guaranteed pattern PT3. [Industrial Applicability]

[0061] According to the present invention, for patterns below the resolution limit in the photomask manufacturing process, it is possible to configure the pattern inspection device so that defects caused by patterns that do not adversely affect the characteristics of the product are not recognized as defects, and it is possible to detect other defects. This reduces the burden on designers who design patterns, and also reduces the workload of workers who inspect patterns in the photomask manufacturing process, and has high industrial applicability. [Explanation of symbols]

[0062] 100 Photomask 1 Transparent substrate 2. First Pattern 3. Second Pattern CT1, CT2, CT3 Judgment Pattern D Resolution limit Df1 First pattern defect Df2 Second pattern defect Df3 Third pattern defect MA Mask Pattern Area MT Mask Pattern PT1 First Design Pattern PT2 Second Design Pattern PT3 Third Design Pattern (Unwarranted Pattern) w Expansion width

Claims

1. A device for inspecting defects in a photomask, The mask pattern data of the photomask, which includes design patterns not covered by the warranty, Using defect data including the location and shape of defects obtained by pattern inspection on the aforementioned photomask, From the aforementioned defect data, the region corresponding to the design pattern outside the warranty is excluded from the defect recognition region that is recognized as a true defect. The pattern inspection apparatus is characterized in that the mask pattern data is composed of a mask pattern generated by expanding the design pattern that is not guaranteed by a predetermined amount.

2. An unguaranteed pattern extraction step for extracting unguaranteed design patterns of the photomask based on a design pattern for forming the photomask pattern, A mask pattern data generation step that generates mask pattern data consisting of mask patterns generated by expanding the aforementioned design pattern outside the guarantee by a predetermined amount, The process includes a pattern inspection step of performing a pattern inspection to detect true defects on the photomask, The region specified by the mask pattern data is excluded from the defect recognition region recognized as a true defect. A method for inspecting the pattern of a photomask, characterized by removing it.

3. The method for inspecting the pattern of a photomask according to claim 2, characterized in that the predetermined amount in the mask pattern data generation step is determined based on the pattern variation caused by the etching step.

4. The method for inspecting a photomask pattern according to claim 2, characterized in that in the mask pattern data generation step, the predetermined amount is determined based on the overlapping misalignment between the design pattern and the optical film pattern.

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