Pattern matching method

Abstract

A pattern matching method calculates pattern densities in a plurality of inspection regions (A1-A10) from design data, divides the pattern densities into a plurality of density groups (PG1-PG3) on the basis of the values, generates images of the plurality of inspection regions by a scanning electron microscope (1), performs pattern matching of a pattern on the images and a CAD pattern, and performs pattern matching of the CAD pattern on the basis of the result of the pattern matching. A plurality of image shift amounts corresponding to each of the plurality of inspection regions (A1-A10) are calculated, the plurality of inspection regions (A1-A10) are divided into a plurality of region groups (AG1-AG3) corresponding to the plurality of density groups (PG1-PG3), and a plurality of correction amounts (C1-C3) corresponding to each of the plurality of region groups (AG1-AG3) are calculated.

Description

Technical Field

[0001] The present invention relates to a method for performing pattern matching between a pattern on an image of a workpiece such as a chip or a glass substrate and a CAD pattern produced based on design data of the pattern, and in particular to a technology for reducing the influence of image offset caused by charge on the workpiece surface on pattern matching. Background Art

[0002] The die-to-database method is a pattern matching method for matching a pattern on an image of a workpiece (e.g., a wafer or a glass substrate) on which a pattern is formed with a CAD pattern produced based on design data of the pattern. More specifically, the die-to-database method obtains the coordinates of an area to be inspected from the design data, moves a stage on which the workpiece is placed to the coordinates, generates a SEM image of the pattern on the workpiece by electron beam irradiation, overlaps the SEM image with the CAD pattern produced based on the design data, creates a grayscale profile of the SEM image within a range set with the edge of the CAD pattern as a starting point, determines the edge of the pattern on the SEM image based on the grayscale profile, and determines a matching position where the offset value of the determined edge and the corresponding CAD pattern edge is minimized.

[0003] In the image generation by the grain-to-database method, the electron beam may be bent due to the influence of the charging of the workpiece surface, resulting in a deviation between the imaging target position and the actual imaging position in some cases. Fig.10 Schematic diagram showing an example of positional deviation between a CAD pattern and a pattern on a SEM image. When the positional deviation between a CAD pattern 501 and a pattern 502 on a SEM image is large, sometimes the matching between the CAD pattern 501 and the pattern 502 on the SEM image fails. Therefore, the offset of the SEM image is calculated based on the deviation when matching the CAD pattern 501 and the pattern 502 on the SEM image, and when the next image is generated, the position of the stage is moved by the offset to minimize the difference between the target position and the actual position. In another method, in order to prevent the failure of pattern matching when it is expected that the influence of charging is large, the matching search range is set larger in advance. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 5-324836 Summary of the invention Problem that the invention aims to solve

[0005] In high-density and simple patterns such as those in memory cells, the influence of charging is not significant because the charging within the workpiece surface is uniform. Therefore, the pattern on the SEM image can be correctly matched with the CAD pattern through the correction of the prior art. However, in workpieces such as logic devices where the pattern density varies greatly, the influence of local charging may be significant.

[0006] Fig.11 This is a schematic diagram showing the charge on the surface of a workpiece with a high pattern density. Fig.12 Schematic diagram showing the charging of the surface of a workpiece with a low pattern density. On the pattern surface 601 of the workpiece, an insulating layer 603 (e.g., an interlayer insulating layer) made of an insulating material and wiring 605 made of a metal such as copper are formed. When the pattern surface 601 is imaged, the electron beam is irradiated onto the pattern surface 601, thereby causing the insulating layer 603 to be charged. Fig.11 and Fig.12 It can be seen from the comparison that in the pattern surface 601 with a small pattern density, the exposed area of ​​the insulating layer 603 is large and the charge is large.

[0007] In this way, if a large charge occurs locally in the pattern surface 601, in the above-mentioned prior art, the actual shooting position sometimes deviates greatly from the shooting target position, resulting in a matching failure. If the range of the search for the matching position is expanded to avoid this situation, errors in the matching position determination will occur, the time used to search for the appropriate matching position will increase, and the processing capacity will decrease.

[0008] Therefore, the present invention provides a technology for reducing the influence of uneven charging of the workpiece surface on pattern matching. Technical means of solving problems

[0009] In one embodiment, a pattern matching method is provided, which sets multiple inspection areas within a pattern surface of a workpiece, calculates the respective pattern densities within the multiple inspection areas based on design data of the pattern of the workpiece, divides the pattern density into multiple density groups based on the numerical value, generates respective images of the multiple inspection areas through a scanning electron microscope, performs pattern matching between the pattern on the image and the corresponding CAD pattern, calculates multiple image offsets respectively corresponding to the multiple inspection areas based on the result of the pattern matching, divides the multiple inspection areas into multiple area groups corresponding to the multiple density groups, calculates multiple correction amounts respectively corresponding to the multiple area groups based on the image offsets corresponding to the inspection areas belonging to each area group, and generates correlation data representing the correlation between the multiple density groups and the multiple correction amounts.

[0010] In one embodiment, the pattern matching method further includes the following steps: the pattern density of the target inspection area on the inspection object workpiece is calculated based on the design data of the pattern in the target inspection area, the inspection object workpiece has a pattern surface with the same structure as the pattern surface of the workpiece, the density group to which the pattern density of the target inspection area belongs is selected from the multiple density groups, the matching exploration distance is corrected using a correction amount corresponding to the selected density group, an image of the target inspection area is generated by a scanning electron microscope, and the corrected matching exploration distance is used to perform pattern matching between the pattern on the image of the target inspection area and the corresponding CAD pattern.

[0011] In one embodiment, the step of correcting the matching search distance is a step of correcting the matching search distance by adding a correction amount corresponding to the selected density group to a reference search distance. In one embodiment, the process of calculating the multiple correction amounts corresponding to the multiple area groups is the following process: calculating the average value and 3σ of the image offset amounts corresponding to the inspection areas belonging to each area group, calculating the correction amount as the sum of the average value and the 3σ for each area group, thereby determining the multiple correction amounts corresponding to the multiple area groups.

[0012] In one embodiment, a pattern matching method is provided, which sets a plurality of inspection areas in a pattern surface of a workpiece, calculates pattern densities of each of the plurality of inspection areas based on design data of the pattern of the workpiece, divides the pattern density into a plurality of density groups based on the value, generates images of each of the plurality of inspection areas by a scanning electron microscope, performs pattern matching between the pattern on the image and the corresponding CAD pattern, calculates a plurality of X-direction image shifts and a plurality of Y-direction image shifts corresponding to the plurality of inspection areas based on the result of the pattern matching, divides the plurality of inspection areas into a plurality of area groups corresponding to the plurality of density groups, calculates a plurality of X-direction correction amounts corresponding to the plurality of area groups based on the X-direction image shifts corresponding to the inspection areas belonging to each area group, calculates a plurality of Y-direction correction amounts corresponding to the plurality of area groups based on the Y-direction image shifts corresponding to the inspection areas belonging to each area group, generates X-direction correlation data indicating correlation between the plurality of density groups and the plurality of X-direction correction amounts, and generates Y-direction correlation data indicating correlation between the plurality of density groups and the plurality of Y-direction correction amounts.

[0013] In one embodiment, the pattern matching method further includes the following steps: calculating a pattern density of a target inspection area on an inspection object workpiece based on design data of a pattern in the target inspection area, the inspection object workpiece having a pattern surface with the same structure as the pattern surface of the workpiece, selecting a density group to which the pattern density of the target inspection area belongs from the plurality of density groups, determining an X-direction correction amount and a Y-direction correction amount corresponding to the selected density group, moving a workpiece stage of a scanning electron microscope supporting the inspection object workpiece in the X direction by the determined X-direction correction amount and in the Y direction by the determined Y-direction correction amount, thereby correcting the position of the workpiece stage, generating an image of the target inspection area of ​​the inspection object workpiece on the workpiece stage whose position is corrected by the scanning electron microscope, and performing pattern matching between the pattern on the image of the target inspection area and the corresponding CAD pattern.

[0014] In one embodiment, the step of calculating the plurality of X-direction correction amounts respectively corresponding to the plurality of region groups is a step of calculating an average value and 3σ of X-direction image shift amounts corresponding to inspection regions belonging to each region group, calculating an X-direction correction amount which is a sum of the average value and 3σ of the X-direction image shift amounts for each region group, and thereby determining the plurality of X-direction correction amounts respectively corresponding to the plurality of region groups. In one embodiment, the process of calculating the multiple Y-direction correction amounts corresponding to the multiple area groups is the following process: calculating the average value and 3σ of the Y-direction image offsets corresponding to the inspection areas belonging to each area group, calculating the Y-direction correction amount as the sum of the average value and 3σ of the Y-direction image offsets for each area group, thereby determining the multiple Y-direction correction amounts corresponding to the multiple area groups. Effects of the Invention

[0015] Based on the relationship between the pattern density of the target inspection area obtained from the design data of the pattern and the statistical image offset caused by the charged SEM image, a correction amount corresponding to the pattern density of the target inspection area is determined. Furthermore, by correcting the matching search distance and / or the stage position according to the pattern density, the accuracy of pattern matching can be improved, and pattern matching can be completed with the minimum matching search time. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram showing one embodiment of an image generation system. Figure 2 It is a schematic diagram showing an example of a plurality of inspection areas. Figure 3 This is a graph showing an example of a plurality of inspection areas and the pattern densities of these inspection areas. Figure 4This is a graph showing an example of a plurality of inspection regions and image shift amounts corresponding to the inspection regions. Figure 5 Yes Figure 3 The pattern density diagram shown is Figure 4 The graphs of image offsets shown are overlaid with the graphs. Figure 6 This is a flowchart for explaining one embodiment of calculating the correction amount of the matching search distance. Figure 7 This is a flowchart for explaining one embodiment of executing pattern matching using a correction amount of a matching search distance. Figure 8 This is a flowchart for explaining one embodiment of calculating the correction amount of the position of the workpiece stage. Fig. 9 This is a flowchart for explaining an embodiment of executing pattern matching using the X-direction correction amount and the Y-direction correction amount of the workpiece stage. Fig.10 This is a schematic diagram showing an example of positional deviation between a CAD pattern and a pattern on a SEM image. Fig.11 This is a schematic diagram showing the charging on the surface of a workpiece with a high pattern density. Fig.12 This is a schematic diagram showing the charging on the surface of a workpiece with a low pattern density. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 1 is a schematic diagram showing an embodiment of an image generation system. The image generation system includes a scanning electron microscope 1 for generating an image of a workpiece W and a processing system 5 for processing the image generated by the scanning electron microscope 1. Examples of the workpiece W include wafers, masks, panels, substrates, etc. used in manufacturing semiconductor devices.

[0018] The processing system 5 is composed of at least one computer. The processing system 5 includes a storage device 5a for storing programs and a computing device 5b for performing operations according to commands included in the programs. The storage device 5a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) and a solid state drive (SSD). Examples of the computing device 5b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the processing system 5 is not limited to this embodiment.

[0019] The processing system 5 may be an edge server connected to the scanning electron microscope 1 via a communication line, may be a cloud server connected to the scanning electron microscope 1 via a communication network such as the Internet or a local area network, or may be a fog computing device (gateway, fog server, router, etc.) provided in a network connected to the scanning electron microscope 1. The processing system 5 may be a combination of multiple servers. For example, the processing system 5 may be a combination of an edge server and a cloud server connected to each other via a communication network such as the Internet or a local area network. In other examples, the processing system 5 may have multiple servers (computers) that are not connected via a network.

[0020] The scanning electron microscope 1 includes an electron gun 15 for emitting an electron beam, a focusing lens 16 for focusing the electron beam emitted from the electron gun 15, an X deflector 17 for deflecting the electron beam in the X direction, a Y deflector 18 for deflecting the electron beam in the Y direction, an objective lens 20 for focusing the electron beam on a workpiece W as an example of a sample, a workpiece stage 31 for supporting the workpiece W, and a stage moving device 35 for translating the workpiece stage 31. The configuration of the electron gun 15 is not particularly limited. For example, a field emission type electron gun or a semiconductor photocathode type electron gun can be used as the electron gun 15.

[0021] The electron beam emitted from the electron gun 15 is focused by the focusing lens 16, and then focused by the objective lens 20 while being deflected by the X deflector 17 and the Y deflector 18, and irradiated onto the surface of the workpiece W. When the primary electrons of the electron beam are irradiated onto the workpiece W, electrons such as secondary electrons and reflected electrons are emitted from the workpiece W. The electrons emitted from the workpiece W are detected by the electron detector 26. The electron detection signal of the electron detector 26 is input to the image acquisition device 28 and converted into an image. Thus, the scanning electron microscope 1 generates an image of the surface of the workpiece W. The image acquisition device 28 is connected to the processing system 5.

[0022] The stage moving device 35 is configured to move the work stage 31 in a direction parallel to the surface of the workpiece W. More specifically, the stage moving device 35 is configured to move the work stage 31 in an X direction and a Y direction perpendicular to the X direction. Both the X direction and the Y direction are horizontal directions parallel to the surface of the workpiece W. The operation of the stage moving device 35 is controlled by the processing system 5.

[0023] Next, an embodiment of a pattern matching method executed by the image generation system will be described. The processing system 5 sets a plurality of inspection areas in the pattern surface (the surface on which the pattern is formed) of the workpiece W. The size and shape of each inspection area are not particularly limited. In one example, each inspection area may be an area corresponding to the field of view (FOV) of the scanning electron microscope 1, or may be a plurality of areas within the field of view (FOV) of the scanning electron microscope 1.

[0024] The processing system 5 calculates the respective pattern densities within a plurality of inspection regions based on the design data of the pattern on the workpiece W. The pattern on the workpiece W is generated based on the design data (also referred to as CAD data). CAD (computer-aided design) is an abbreviation for computer-aided design. The design data is pre-stored in the storage device 5a of the processing system 5. The pattern density is defined as the ratio of the total area of the pattern within the inspection region to the total area of the inspection region. Pattern density (%) = Total area of the pattern within the inspection region / Total area of the inspection region × 100

[0025] Figure 2 is a schematic diagram showing an example of a plurality of inspection regions. There are pattern and non-pattern regions within the inspection regions A1, A2, and A3. The pattern is made of metal, and the non-pattern region is made of an insulating material. The shape and area of the pattern generally vary according to each inspection region. Therefore, the pattern density of each inspection region also varies. In Figure 2 three inspection regions A1, A2, and A3 are shown, but more inspection regions are provided within the pattern surface of one workpiece W.

[0026] The processing system 5 divides the plurality of pattern densities of the plurality of inspection regions into a plurality of density groups based on this value. In the present embodiment, a plurality of thresholds are used to classify the plurality of pattern densities. For example, the processing system 5 divides the plurality of pattern densities into a first density group less than the first threshold, a second density group between the first threshold and the second threshold (the first threshold < the second threshold), and a third density group greater than the second threshold. The plurality of thresholds can be a plurality of discrete values within the range of 0% to 100%, or continuous values of 0% to 100%.

[0027] Figure 3 is a chart showing an example of a plurality of inspection regions and the pattern densities of these inspection regions. In Figure 3 the vertical axis represents the pattern density (%), and the horizontal axis represents the number of the inspection region. In the example of Figure 3 according to the first threshold T1 and the second threshold T2 (T1 < T2), the plurality of pattern densities are divided into three density groups DG1, DG2, and DG3.

[0028] Next, the processing system 5 issues an instruction to the scanning electron microscope 1 to generate respective images of the plurality of inspection regions through the scanning electron microscope 1. The plurality of images of the plurality of inspection regions are stored in the storage device 5a of the processing system 5. The processing system 5 performs pattern matching between the pattern on each image and the corresponding CAD pattern. The CAD pattern is a virtual pattern generated by the processing system 5 based on pattern design information included in the design data of the pattern formed on the pattern surface of the workpiece W. The pattern matching is performed based on the die-to-database method.

[0029] The processing system 5 calculates a plurality of image offsets corresponding to the plurality of inspection areas, respectively, based on the pattern matching result. The image offset is represented by a vector of deviations between the pattern on the image and the corresponding CAD pattern. That is, the image offset is represented by the square root of the sum of the squares of the offset in the X direction as the X component of the vector and the offset in the Y direction as the Y component of the vector. Depending on the shape of the pattern, the image offset may also be represented by the offset in the X direction or the offset in the Y direction.

[0030] Figure 4 : is a graph showing an example of a plurality of inspection areas and image shift amounts corresponding to the inspection areas. Figure 4 In FIG. 5 , the vertical axis represents the image offset and the horizontal axis represents the number of the inspection area. The processing system 5 may also calculate a moving average of the image offset along the arrangement direction of the inspection area. In one embodiment, the image offset may be a moving average of the image offset.

[0031] Figure 5 Yes Figure 3 The pattern density diagram shown and Figure 4 The graphs of image offsets shown are superimposed on the graphs. Figure 5 In the figure, the right vertical axis represents the image offset, the left vertical axis represents the pattern density, and the horizontal axis represents the number of the inspection area. Figure 5 In the example shown, the processing system 5 divides the plurality of inspection areas into a plurality of area groups AG1, AG2, AG3 corresponding to the plurality of density groups DG1, DG2, DG3. Figure 5 In the example shown, inspection areas A1, A5, and A6 belonging to density group DG1 are classified into area group AG1, inspection areas A2, A7, and A8 belonging to density group DG2 are classified into area group AG2, and inspection areas A3, A4, A9, and A10 belonging to density group DG3 are classified into area group AG3.

[0032] The processing system 5 calculates a plurality of correction amounts corresponding to the plurality of region groups, respectively, based on the image shift amounts corresponding to the inspection regions belonging to the respective region groups. Figure 5In the example shown, the processing system 5 calculates the correction amount C1 corresponding to the area group AG1 based on the image shift amounts corresponding to the inspection areas A1, A5, and A6 belonging to the area group AG1. The image shift amount may also be a moving average along the arrangement direction of the inspection areas. The correction amount C1 is the value obtained by adding 3σ to the average value Av1 of the image shift amounts corresponding to the inspection areas A1, A5, and A6 (i.e., C1=Av1+3σ). The symbol σ represents the standard deviation.

[0033] Similarly, the processing system 5 calculates the correction amount C2 corresponding to the area group AG2 (i.e., C2=Av2+3σ) based on the image offset corresponding to the inspection areas A2, A7, and A8 belonging to the area group AG2, and calculates the correction amount C3 corresponding to the area group AG3 (i.e., C3=Av3+3σ) based on the image offset corresponding to the inspection areas A3, A4, A9, and A10 belonging to the area group AG3.

[0034] As described above, the correction amounts C1, C2, and C3 are determined for the area groups AG1, AG2, and AG3, respectively. Figure 5 It can be seen that the plurality of area groups AG1, AG2, AG3 correspond to the plurality of density groups DG1, DG2, DG3. Therefore, the correction amounts C1, C2, C3 correspond to the density groups DG1, DG2, DG3, respectively. The processing system 5 generates correlation data indicating the correlation between the plurality of density groups DG1, DG2, DG3 and the plurality of correction amounts C1, C2, C3, and stores the correlation data in the storage device 5a. The correlation data may be a table indicating the correlation between the plurality of density groups and the plurality of correction amounts, or may be a relational expression.

[0035] Next, an embodiment of performing pattern matching using the correction amounts C1, C2, and C3 obtained as described above will be described. The processing system 5 calculates the pattern density of the target inspection area on the inspection object workpiece based on the design data of the pattern in the target inspection area. The design data of the pattern in the target inspection area is stored in advance in the storage device 5a of the processing system 5.

[0036] The inspection object workpiece is a workpiece having a pattern surface with the same structure as the pattern surface of the above-mentioned workpiece W used to generate the correlation data representing the correlation between the plurality of density groups DG1, DG2, DG3 and the plurality of correction amounts C1, C2, C3. For example, if the pattern surface of the workpiece W used to generate the correlation data has a gate structure, the pattern surface of the inspection object workpiece also has a gate structure. The workpiece W and the inspection object workpiece have the same surface structure and the same surface material. In this specification, "same" means not only completely the same, but also substantially the same according to technical common sense.

[0037] The processing system 5 selects a density group to which the pattern density of the target inspection area belongs from the plurality of density groups DG1, DG2, and DG3. In addition, the processing system 5 corrects the matching search distance using a correction amount corresponding to the selected density group. For example, when the density group DG2 is selected as the density group to which the pattern density of the target inspection area belongs, the processing system 5 corrects the matching search distance using a correction amount C2 corresponding to the density group DG2.

[0038] The matching exploration distance is the distance (or range) from the edge of the CAD pattern generated based on the design data of the pattern in the target inspection area, and the edge of the pattern on the image is searched within the matching exploration distance. According to this embodiment, the matching exploration distance is corrected according to the pattern density of the target inspection area. Since the pattern density affects the charge amount, in other words, the matching exploration distance is corrected according to the charge amount of the target inspection area.

[0039] In one embodiment, the processing system 5 corrects the matching exploration distance by adding the correction amount corresponding to the selected density group to the reference exploration distance. As an example of the reference exploration distance, a value of half the maximum spacing of the pattern in the target inspection area can be cited. The value of half the maximum spacing of the pattern is the minimum distance (range) at which pattern matching can be successfully performed. In one example, if the selected density group is DG2, the correction amount is C2, and the maximum spacing of the pattern in the target inspection area is set to PT, then the corrected matching exploration distance is expressed as PT / 2+C2.

[0040] The processing system 5 generates an image of the target inspection area through the scanning electron microscope 1, acquires the image of the target inspection area from the scanning electron microscope 1, and performs pattern matching of the pattern on the image of the target inspection area with the corresponding CAD pattern using the corrected matching exploration distance. Since the processing system 5 explores the edge on the image within the corrected matching exploration distance, pattern matching can be performed accurately and with a minimum exploration time.

[0041] Figure 6 This is a flowchart for explaining one embodiment of calculating the correction amount of the matching search distance. In step 101 , the processing system 5 sets a plurality of inspection areas in the pattern surface of the workpiece W. The number of inspection areas is not particularly limited, but 100 or more inspection areas may be set. In step 102 , the processing system 5 calculates the pattern density of each of the plurality of inspection areas set in step 101 based on the design data of the pattern on the workpiece W. In step 103, the processing system 5 divides the plurality of pattern densities calculated in step 102 into a plurality of density groups according to their values. Specifically, the processing system 5 divides the plurality of pattern densities into a plurality of density groups using a plurality of thresholds.

[0042] In step 104 , the processing system 5 issues a command to the scanning electron microscope 1 , so that the scanning electron microscope 1 generates images of each of the plurality of inspection regions set in step 101 . In step 105, the processing system 5 performs pattern matching between the patterns on each image of the plurality of inspection regions and the corresponding CAD patterns. The pattern matching can be performed according to a known method. In step 106 , the processing system 5 calculates a plurality of image shift amounts corresponding to the plurality of inspection regions, respectively, based on the result of the pattern matching.

[0043] In step 107, the processing system 5 divides the plurality of inspection areas into a plurality of area groups corresponding to the plurality of density groups set in step 103 (see Figure 5 ). In step 108, the processing system 5 calculates a plurality of correction amounts corresponding to the plurality of area groups, respectively, based on the image shift amounts corresponding to the inspection areas belonging to each area group. More specifically, the processing system 5 calculates the average value and 3σ of the image shift amounts in each area group, and calculates the correction amount as the sum of the average value and 3σ for each area group. The image shift amount may also be a moving average value of the image shift amounts along the arrangement direction of the inspection areas. In step 109 , the processing system 5 generates correlation data indicating the correlation between the plurality of density groups and the plurality of correction amounts, and stores the data in the storage device 5 a .

[0044] Figure 7 This is a flowchart for explaining one embodiment of executing pattern matching using a correction amount of a matching search distance. In step 201 , the processing system 5 calculates the pattern density of the target inspection area on the inspection target workpiece having a pattern surface having the same structure as the pattern surface of the workpiece W based on the design data of the pattern in the target inspection area. In step 202 , the processing system 5 selects a density group to which the pattern density of the target inspection area belongs from among the plurality of density groups determined in step 103 .

[0045] In step 203, the processing system 5 corrects the matching search distance using the correction amount corresponding to the density group selected in step 202. The correction amount corresponding to the selected density group is uniquely determined based on the correlation data generated in step 109 described above. In step 204 , the processing system 5 sends an instruction to the scanning electron microscope 1 , so that the scanning electron microscope 1 generates an image of the target inspection area. In step 205 , the processing system 5 acquires an image of the target inspection area from the scanning electron microscope 1 , and uses the matching search distance corrected in step 203 to perform pattern matching between the pattern on the image of the target inspection area and the corresponding CAD pattern.

[0046] Below, refer to Figure 8 and Fig. 9 Another embodiment of pattern matching is described. In this embodiment, the processing system 5 modifies Figure 1 The position of the workpiece stage 31 shown in the figure is used instead of the correction matching search distance to reduce the image offset of the target inspection area itself. The structure and operation of this embodiment not specifically described are similar to those of the reference Figures 1 to 7 The above-described embodiments are the same, and thus repeated descriptions thereof will be omitted.

[0047] Figure 8 This is a flowchart for explaining one embodiment of calculating the correction amount of the position of the work stage 31 . Figure 8 Steps 301 to 305 and Figure 6 Steps 101 to 105 are the same, so their repeated description is omitted. In step 306, the processing system 5 calculates a plurality of X-direction image offsets and a plurality of Y-direction image offsets corresponding to the plurality of inspection areas, respectively, based on the pattern matching result in step 305. The X-direction image offset is the image offset in the X direction, and the Y-direction image offset is the image offset in the Y direction perpendicular to the X direction. In step 307, the processing system 5 divides the plurality of inspection areas into a plurality of area groups corresponding to the plurality of density groups set in step 303 (see Figure 5 ).

[0048] In step 308, the processing system 5 calculates a plurality of X-direction correction amounts corresponding to the plurality of region groups, based on the X-direction image shift amounts corresponding to the inspection regions belonging to each region group. More specifically, the processing system 5 calculates the average value and 3σ of the X-direction image shift amounts in each region group, calculates the X-direction correction amount as the sum of the average value and 3σ of the X-direction image shift amounts for each region group, and thereby determines the plurality of X-direction correction amounts corresponding to the plurality of region groups. The X-direction image shift amount may also be a moving average value of the X-direction image shift amounts along the arrangement direction of the inspection regions.

[0049] In step 309, the processing system 5 calculates a plurality of Y-direction correction amounts corresponding to the plurality of region groups, based on the Y-direction image shift amounts corresponding to the inspection regions belonging to each region group. More specifically, the processing system 5 calculates the average value and 3σ of the Y-direction image shift amounts in each region group, calculates the Y-direction correction amount as the sum of the average value and 3σ of the Y-direction image shift amounts for each region group, and thereby determines the plurality of Y-direction correction amounts corresponding to the plurality of region groups. The Y-direction image shift amount may also be a moving average value of the Y-direction image shift amounts along the arrangement direction of the inspection regions.

[0050] The above step 308 may be performed after the above step 309 or simultaneously with the above step 309 . In step 310, the processing system 5 generates X-direction correlation data indicating the correlation between the plurality of density groups and the plurality of X-direction correction amounts, generates Y-direction correlation data indicating the correlation between the plurality of density groups and the plurality of Y-direction correction amounts, and stores the X-direction correlation data and the Y-direction correlation data in the storage device 5a.

[0051] Fig. 9 This is a flowchart for explaining an embodiment of executing pattern matching using the X-direction correction amount and the Y-direction correction amount of the work stage 31 . In step 401 , the processing system 5 calculates the pattern density of the target inspection area on the inspection target workpiece having a pattern surface having the same structure as the pattern surface of the workpiece W based on the design data of the pattern in the target inspection area. In step 402 , the processing system 5 selects a density group to which the pattern density of the target inspection area belongs from among the plurality of density groups determined in step 303 .

[0052] In step 403, the processing system 5 determines the X-direction correction amount and the Y-direction correction amount corresponding to the density group selected in step 402. The X-direction correction amount is uniquely determined based on the X-direction correlation data, and the Y-direction correction amount is uniquely determined based on the Y-direction correlation data. In step 404, the processing system 5 issues a command to the scanning electron microscope 1 to move the work stage 31 of the scanning electron microscope 1 supporting the inspection target workpiece in the X direction by the determined X direction correction amount and in the Y direction by the determined Y direction correction amount, thereby correcting the position of the work stage 31. Sometimes, one of the X direction correction amount or the Y direction correction amount is 0.

[0053] In step 405 , the processing system 5 issues a command to the scanning electron microscope 1 , so that the scanning electron microscope 1 generates an image of the target inspection area of ​​the inspection object workpiece on the workpiece stage 31 after the position of the inspection object workpiece is corrected. In step 406 , the processing system 5 performs pattern matching of the pattern on the image of the target inspection area with the corresponding CAD pattern. According to this embodiment, since the position of the workpiece stage 31 is corrected according to the pattern density, the image shift of the target inspection area itself is reduced. As a result, the accuracy of pattern matching is improved, and pattern matching is performed with a minimum search time.

[0054] Reference Figure 6 and Figure 7 Flowcharts illustrating the implementation of the method and reference Figure 8 and Fig. 9 The embodiments described in the flowcharts of can also be combined. That is, both the matching search distance and the position of the workpiece stage 31 can be corrected according to the pattern density of the target inspection area.

[0055] The above-mentioned embodiments are recorded for the purpose of enabling a person with common knowledge in the technical field to which the present invention belongs to implement the present invention. Those skilled in the art can certainly make various modifications to the above-mentioned embodiments, and the technical idea of ​​the present invention can also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is interpreted as the widest scope of the technical idea defined by the claims. Possibility of Industrial Application

[0056] The present invention can be used as a technology for reducing the influence of image deviation caused by charging of the workpiece surface on pattern matching. Explanation of symbols

[0057] 1 Scanning electron microscopy 5. Processing System 15Electron Gun 16 Focusing lens 17 X Deflector 18 Y deflector 20 objective lens 26 electronic detector 28 Image acquisition device 31 workpiece table 35 stage moving device.

Claims

1. A pattern matching method, characterized in that: Set multiple inspection areas within the pattern surface of the workpiece. calculating the pattern density of each of the plurality of inspection areas according to the design data of the pattern of the workpiece, The pattern density is divided into a plurality of density groups according to the value, generating respective images of the plurality of inspection regions by means of a scanning electron microscope, performing pattern matching of the pattern on the image with a corresponding CAD pattern, According to the pattern matching result, a plurality of image offsets corresponding to the plurality of inspection areas are calculated, dividing the plurality of inspection areas into a plurality of area groups corresponding to the plurality of density groups, calculating a plurality of correction amounts corresponding to the plurality of region groups, respectively, based on the image shift amounts corresponding to the inspection regions belonging to the respective region groups; Correlation data indicating a correlation between the plurality of density groups and the plurality of correction amounts is generated.

2. The pattern matching method according to claim 1, characterized in that: It also includes the following steps: The pattern density of a target inspection area on an inspection target workpiece is calculated based on design data of a pattern in the target inspection area, the inspection target workpiece having a pattern surface having the same structure as the pattern surface of the workpiece, selecting a density group to which the pattern density of the target inspection area belongs from among the plurality of density groups, Correcting the matching exploration distance using a correction amount corresponding to the selected density group, generating an image of the target inspection area by a scanning electron microscope, Using the corrected matching search distance, pattern matching of the pattern on the image of the target inspection area and the corresponding CAD pattern is performed.

3. The pattern matching method according to claim 2, characterized in that: The step of correcting the matching search distance is a step of correcting the matching search distance by adding a correction amount corresponding to the selected density group to the reference search distance.

4. The pattern matching method according to claim 1, characterized in that: The step of calculating the plurality of correction amounts corresponding to the plurality of region groups, respectively, is the following step: Calculate the average value and 3σ of the image shift amount corresponding to the inspection area belonging to each area group, By calculating the correction amount as the sum of the average value and the 3σ for each region group, a plurality of correction amounts corresponding to the plurality of region groups, respectively, are determined.

5. A pattern matching method, characterized in that: Set multiple inspection areas within the pattern surface of the workpiece. calculating the pattern density of each of the plurality of inspection areas according to the design data of the pattern of the workpiece, The pattern density is divided into a plurality of density groups according to the value, generating respective images of the plurality of inspection regions by means of a scanning electron microscope, performing pattern matching of the pattern on the image with a corresponding CAD pattern, According to the pattern matching result, a plurality of X-direction image offsets and a plurality of Y-direction image offsets corresponding to the plurality of inspection areas are calculated, dividing the plurality of inspection areas into a plurality of area groups corresponding to the plurality of density groups, calculating a plurality of X-direction correction amounts corresponding to the plurality of region groups, respectively, based on the X-direction image shift amounts corresponding to the inspection regions belonging to each region group; calculating a plurality of Y-direction correction amounts corresponding to the plurality of region groups, respectively, based on the Y-direction image shift amounts corresponding to the inspection regions belonging to each region group; generating X-direction correlation data indicating correlation between the plurality of density groups and the plurality of X-direction correction amounts, Y-direction correlation data indicating a correlation between the plurality of density groups and the plurality of Y-direction correction amounts is generated.

6. The pattern matching method according to claim 5, characterized in that: It also includes the following steps: The pattern density of a target inspection area on an inspection target workpiece is calculated based on design data of a pattern in the target inspection area, the inspection target workpiece having a pattern surface having the same structure as the pattern surface of the workpiece, selecting a density group to which the pattern density of the target inspection area belongs from among the plurality of density groups, determining an X-direction correction amount and a Y-direction correction amount corresponding to the selected density group, The work stage of the scanning electron microscope supporting the inspection target workpiece is moved in the X direction by the determined X direction correction amount and in the Y direction by the determined Y direction correction amount, thereby correcting the position of the work stage. generating, by the scanning electron microscope, an image of the target inspection area of ​​the inspection object workpiece on the workpiece stage whose position is corrected; Pattern matching of the pattern on the image of the target inspection area with the corresponding CAD pattern is performed.

7. The pattern matching method according to claim 5, characterized in that: The step of calculating the plurality of X-direction correction amounts corresponding to the plurality of region groups, respectively, is the following step: Calculate the average value and 3σ of the X-direction image deviation corresponding to the inspection area belonging to each area group, By calculating an X-direction correction amount that is a sum of an average value of the X-direction image shift amount and 3σ for each region group, a plurality of X-direction correction amounts corresponding to the plurality of region groups, respectively, are determined.

8. The pattern matching method according to claim 5, characterized in that: The step of calculating the plurality of Y-direction correction amounts respectively corresponding to the plurality of region groups is the following step: Calculate the average value and 3σ of the Y-direction image shift corresponding to the inspection area belonging to each area group, By calculating the Y-direction correction amount as the sum of the average value of the Y-direction image shift amount and 3σ for each region group, a plurality of Y-direction correction amounts corresponding to the plurality of region groups, respectively, are determined.

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