Pattern measuring method and pattern measuring device

Abstract

To provide a pattern measuring method and device which acquire information on a pattern from design data, and correctly measure a distance between the patterns on an image, on the basis of the information.SOLUTION: A pattern measuring method: connects an extension line 105 having a predetermined length to an end part of a first CAD edge 101a of a first CAD pattern 101; determines a second CAD pattern 102 which has a second CAD edge 102a which exists within a predetermined search range in a normal direction from the extension line 105; acquires first pattern information including the number of a layer which the first CAD pattern 101 belongs to, and second pattern information including the number of the layer which the second CAD pattern 102 belongs to from design data; detects a first actual edge and a second actual edge on an image by using an edge detection parameter; and measures a distance L in the normal direction of the first actual edge and the second actual edge.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technique for measuring the distance between patterns formed on a workpiece such as a wafer, a mask, a panel, or a substrate, and more particularly to a technique for measuring the distance between patterns on an image generated by an image generating device such as a scanning electron microscope. [Background technology]

[0002] Workpieces such as wafers, masks, panels, and substrates have multi-layer surface structures in which multiple patterns are formed on multiple layers. To inspect the patterns formed on the workpiece, images of the patterns are generated using a scanning electron microscope, and the distances between the patterns on the images are measured.

[0003] Recently, the accelerating voltage of the electron beam in a scanning electron microscope has been increased to generate images of not only the top layer but also the layers below it. Images generated under these high accelerating voltage conditions show multiple overlapping patterns in multiple layers, as shown in Figure 10. In image 500 shown in Figure 10, pattern 501 is in a first layer, pattern 502 is in a second layer below the first layer, and pattern 503 is in a third layer below the second layer.

[0004] Pattern 501 in the first layer is made of a material that is opaque to the electron beam, and pattern 502 in the second layer is made of a material that is transparent to the electron beam. Therefore, part of pattern 503 in the third layer is hidden by pattern 501 and cannot be seen, but another part of pattern 503 can be seen through pattern 502.

[0005] When measuring the distance between patterns on image 500, several ROIs (regions of interest) are set on image 500. In Fig. 10, ROI1 is set to measure the length of the portion of pattern 501 that protrudes from pattern 503. ROI2 is set to measure the distance between pattern 501 and pattern 502. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-243993 Summary of the Invention [Problem to be solved by the invention]

[0007] In ROI1, the distance between edge 501a of pattern 501 and edge 503a of pattern 503 is measured. Therefore, before measuring the distance, edges 501a and 503a on image 500 are first detected based on changes in brightness within image 500. Because pattern 501 is made of a non-transparent material, edge 503a of pattern 503 does not appear on image 500 in the area where pattern 501 and pattern 503 overlap. Therefore, as shown in FIG. 10, edge 503a of pattern 503 outside pattern 501 is detected.

[0008] 11 is a diagram showing an example of a method for measuring the distance between edges 501a and 503a on an image 500. The position of intersection P501 between the brightness profile BP501 of edge 501a and the edge threshold value represents the position of edge 501a. The position of intersection P503 between the brightness profile BP503 of edge 503a and the edge threshold value represents the position of edge 503a. The distance L between edges 501a and 503a can be found from the positions of intersection P501 and P503.

[0009] However, the position of the edge 503a of the pattern 503 is easily affected by the brightness of the adjacent pattern 501 within the ROI1. For example, FIG. 12 is a diagram showing an example in which the pattern 501 within the ROI1 is thicker than the example in FIG. 11. In this example, the brightness profile BP503 of the edge 503a changes due to the influence of the brightness of the pattern 501. The position of the intersection P503 between the brightness profile BP503 of the edge 503a and the edge threshold also changes due to the change in the brightness profile BP503. As a result, the distance L between the edge 501a and the edge 503a is not measured correctly.

[0010] In ROI2 shown in Fig. 10, the distance between edge 501b of pattern 501 and edge 502a of pattern 502 is measured. Therefore, before the distance measurement, edges 501b and 502a on image 500 are first detected based on changes in brightness within image 500. Specifically, as shown in Fig. 13, a brightness profile is created across ROI2, and a position P1 of edge 501b and a position P2 of edge 502a, which are the intersections between the edge detection threshold and the brightness profile, are determined.

[0011] On image 500, it is impossible to distinguish that patterns 501 and 502 belong to different layers, so the same edge detection threshold is used. However, the edge detection threshold suitable for the first layer to which pattern 501 belongs is usually different from the edge detection threshold suitable for the second layer to which pattern 502 belongs. For this reason, if the same edge detection threshold is used, the position P1 of edge 501b or the position P2 of edge 502a may not be detected correctly. As a result, there is a risk that the distance between edge 501b and edge 502a may not be measured correctly.

[0012] Therefore, the present invention provides a technique that can acquire pattern information from design data and, based on that information, correctly measure the distance between patterns on an image. [Means for solving the problem]

[0013] In one aspect, a pattern measurement method is provided for measuring the distance between multiple patterns on an image, the pattern measurement method including: connecting an extension line of a predetermined length to an end of a first CAD edge of a first CAD pattern; determining a second CAD pattern having a second CAD edge that exists within a predetermined search range in a normal direction from the extension line; obtaining first pattern information including a layer number to which the first CAD pattern belongs and second pattern information including a layer number to which the second CAD pattern belongs from design data; detecting a first actual edge and a second actual edge on the image corresponding to the first CAD edge and the second CAD edge using edge detection parameters; and measuring the distance between the first actual edge and the second actual edge in the normal direction.

[0014] In one embodiment, the layer to which the second CAD pattern belongs is different from the layer to which the first CAD pattern belongs. In one embodiment, the second CAD pattern belongs to the same layer as the first CAD pattern. In one embodiment, the edge detection parameters include a first edge detection parameter predetermined for a layer to which the first CAD pattern belongs, and a second edge detection parameter predetermined for a layer to which the second CAD pattern belongs. In one embodiment, the edge detection parameters include a peak search range and a bottom search range of an intensity profile of the actual pattern, and an edge detection threshold on the intensity profile. In one embodiment, the pattern measurement method further includes assigning orientation information to a plurality of CAD edges constituting each of the first CAD pattern and the second CAD pattern according to a predetermined rule, and assigning an attribute of one of line, space, or pitch to a pair of the first actual edge and the second actual edge based on the orientation of the first CAD edge and the orientation of the second CAD edge indicated in the orientation information. In one aspect, when the orientation of the first CAD edge is a first orientation and the orientation of the second CAD edge is a second orientation opposite to the first orientation, a line attribute is assigned to the pair of the first actual edge and the second actual edge; when the orientation of the first CAD edge is the second orientation and the orientation of the second CAD edge is the first orientation, a space attribute is assigned to the pair of the first actual edge and the second actual edge; and when the orientations of the first CAD edge and the second CAD edge are both the first orientation or the second orientation, a pitch attribute is assigned to the pair of the first actual edge and the second actual edge. In one embodiment, the layer to which the second CAD pattern belongs is below the layer to which the first CAD pattern belongs, and the pattern measurement method further includes designating each of the first CAD pattern and the second CAD pattern as either a transparent pattern or a non-transparent pattern.

[0015] In one aspect, a pattern measuring device for measuring the distance between multiple patterns on an image is provided, comprising: a storage device storing a program and design data; and an arithmetic unit that performs calculations in accordance with instructions included in the program, wherein the program is configured to cause the arithmetic unit to perform the following operations: connect an extension line of a predetermined length to an end of a first CAD edge of a first CAD pattern; determine a second CAD pattern having a second CAD edge that exists within a predetermined search range in a normal direction from the extension line; obtain from the design data first pattern information including a layer number to which the first CAD pattern belongs, and second pattern information including a layer number to which the second CAD pattern belongs; detect first and second real edges on the image corresponding to the first and second CAD edges using edge detection parameters; and measure the distance between the first and second real edges in the normal direction.

[0016] In one embodiment, the layer to which the second CAD pattern belongs is different from the layer to which the first CAD pattern belongs. In one embodiment, the second CAD pattern belongs to the same layer as the first CAD pattern. In one embodiment, the edge detection parameters include a first edge detection parameter predetermined for a layer to which the first CAD pattern belongs, and a second edge detection parameter predetermined for a layer to which the second CAD pattern belongs. In one embodiment, the edge detection parameters include a peak search range and a bottom search range of an intensity profile of the actual pattern, and an edge detection threshold on the intensity profile. In one embodiment, the program is configured to cause the arithmetic device to perform an operation of assigning orientation information to a plurality of CAD edges constituting each of the first CAD pattern and the second CAD pattern according to a predetermined rule, and assigning one of the attributes of line, space, or pitch to a pair of the first actual edge and the second actual edge based on the orientation of the first CAD edge and the orientation of the second CAD edge indicated in the orientation information. In one aspect, the program is configured to cause the arithmetic device to perform the following operations: when the orientation of the first CAD edge is a first orientation and the orientation of the second CAD edge is a second orientation opposite to the first orientation, assign a line attribute to the pair of the first actual edge and the second actual edge; when the orientation of the first CAD edge is the second orientation and the orientation of the second CAD edge is the first orientation, assign a space attribute to the pair of the first actual edge and the second actual edge; and when the orientation of the first CAD edge and the orientation of the second CAD edge are both the first orientation or the second orientation, assign a pitch attribute to the pair of the first actual edge and the second actual edge. In one embodiment, the layer to which the second CAD pattern belongs is below the layer to which the first CAD pattern belongs, and the program is configured to cause the computing device to perform an operation of designating each of the first CAD pattern and the second CAD pattern as either a transparent pattern or a non-transparent pattern. [Effects of the Invention]

[0017] According to the present invention, information (such as the relative position between edges, layers, etc.) of the first and second CAD patterns corresponding to the actual pattern to be measured can be obtained from the design data. Based on this information, the distance between the patterns can be accurately measured. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of an image generating device. [Figure 2] FIG. 2 is a schematic diagram showing an example of a CAD pattern included in design data. [Figure 3] 10 is a schematic diagram showing an example of an image in which a first real pattern and a second real pattern corresponding to a first CAD pattern and a second CAD pattern appear. FIG. [Figure 4] 10A to 10C are diagrams illustrating an embodiment of a step of detecting a first actual edge. [Figure 5] FIG. 10 is a schematic diagram showing an example of an image in which a third real pattern exists between a first real pattern and a second real pattern; [Figure 6] FIG. 10 is a schematic diagram showing an example in which a plurality of CAD patterns belonging to the same layer are arranged alternately. [Figure 7] 10A and 10B are schematic diagrams illustrating an operation of adding orientation information to a plurality of CAD edges that form each of the first CAD pattern and the second CAD pattern. [Figure 8] FIG. 10 is a diagram illustrating attributes of lines, spaces, and pitches. [Figure 9] FIG. 10 is a schematic diagram showing an example of an image of an actual pattern formed in three layers. [Figure 10] FIG. 1 is a schematic diagram showing an example of an image in which multiple patterns in multiple layers appear overlapping one another. [Figure 11] FIG. 1 is a diagram showing an example of a conventional method for measuring the distance between two edges on an image. [Figure 12] FIG. 10 is a diagram showing an example in which the distance between two edges changes due to a change in the shape of a pattern. [Figure 13] FIG. 11 is a diagram showing an example of a luminance profile within ROI2 shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram showing one embodiment of an image generation apparatus. The image generation apparatus includes a scanning electron microscope 1 that generates an image of a workpiece W, and a pattern measurement apparatus 5 that measures the distance between patterns on the image generated by the scanning electron microscope 1. Examples of workpieces W include wafers, masks, panels, and substrates used in the manufacture of semiconductor devices.

[0020] The pattern measurement device 5 is composed of at least one computer. The pattern measurement device 5 includes a storage device 5a in which a program is stored, and an arithmetic device 5b that executes calculations according to instructions included in the program. The storage device 5a includes a main storage device such as RAM, and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the arithmetic device 5b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the pattern measurement device 5 is not limited to these examples.

[0021] The pattern measurement device 5 may be an edge server connected to the scanning electron microscope 1 via a communication line, or may be a cloud server connected to the scanning electron microscope 1 via a communication network such as the Internet or a local network, or may be a fog computing device (gateway, fog server, router, etc.) installed in a network connected to the scanning electron microscope 1. The pattern measurement device 5 may also be a combination of multiple servers. For example, the pattern measurement device 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 network.

[0022] The scanning electron microscope 1 has an electron gun 15 that emits an electron beam, a focusing lens 16 that focuses the electron beam emitted from the electron gun 15, an X deflector 17 that deflects the electron beam in the X direction, a Y deflector 18 that deflects the electron beam in the Y direction, an objective lens 20 that focuses the electron beam on a workpiece W, which is an example of a specimen, and a stage 31 that supports the workpiece W. The configuration of the electron gun 15 is not particularly limited. For example, a field emitter electron gun or a semiconductor photocathode electron gun can be used as the electron gun 15.

[0023] The electron beam emitted from the electron gun 15 is focused by a focusing lens 16, and then deflected by an X deflector 17 and a Y deflector 18 while being focused by an objective lens 20, and is then 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 backscattered electrons are emitted from the workpiece W. The electrons emitted from the workpiece W are detected by an electron detector 26. An electron detection signal from the electron detector 26 is input to an image acquisition device 28 and converted into an image. In this way, the scanning electron microscope 1 generates an image of the surface of the workpiece W. The image acquisition device 28 is connected to a pattern measurement device 5, and the image of the workpiece W is sent to the pattern measurement device 5.

[0024] The following describes a method for measuring the distance between patterns on an image generated by a scanning electron microscope 1. In the following description, the patterns on the workpiece W are formed based on design data (also referred to as CAD data). CAD is an abbreviation for computer-aided design.

[0025] Design data for the pattern formed on the workpiece W is stored in advance in the storage device 5a. The design data includes pattern information such as the coordinates of the vertices of the pattern formed on the workpiece W, the position, shape, and size of the pattern, and the number of the layer to which the pattern belongs. The operation control unit 5 is capable of reading the design data for the pattern from the storage device 5a.

[0026] The CAD pattern included in the design data described below is a virtual pattern defined by the pattern information included in the design data, and has a polygonal shape. In the following description, the pattern that is actually formed on the workpiece W and appears in the image may be referred to as the real pattern.

[0027] 2 is a schematic diagram showing an example of CAD patterns included in design data. A first CAD pattern 101 belongs to a first layer, and a second CAD pattern 102 belongs to a second layer. The first layer and the second layer are different layers, and the second layer exists below the first layer. The second layer may also exist above the first layer.

[0028] The pattern measuring device 5 connects an extension line 105 of a predetermined length to an end of the first CAD edge 101a of the first CAD pattern 101. The longitudinal direction of the extension line 105 coincides with the longitudinal direction of the first CAD edge 101a. The length of the extension line 105 is not particularly limited, but the length of the extension line 105 may be equal to or shorter than the length of the first CAD edge 101a, or may be equal to or longer than the length of the first CAD edge 101a.

[0029] The pattern measuring device 5 determines a predetermined search range S centered on the extension line 105. The search direction of the search range S is normal to the extension line 105 and the first CAD edge 101a (i.e., perpendicular to the extension line 105 and the first CAD edge 101a). The pattern measuring device 5 searches the search range S in the normal direction from the extension line 105, and determines the second CAD pattern 102 having the second CAD edge 102a that exists within the search range S.

[0030] The pattern measuring device 5 acquires, from the design data, first pattern information including the layer number to which the first CAD pattern 101 belongs and second pattern information including the layer number to which the second CAD pattern 102 belongs. The first pattern information includes the coordinates of the vertices of the first CAD pattern 101, the position, shape, and size of the first CAD pattern 101, and the layer number to which the first CAD pattern 101 belongs. The second pattern information includes the coordinates of the vertices of the second CAD pattern 102, the position, shape, and size of the second CAD pattern 102, and the layer number to which the second CAD pattern 102 belongs.

[0031] 3 is a schematic diagram showing an example of an image 200 in which a first actual pattern 201 and a second actual pattern 202 appear, which correspond to the first CAD pattern 101 and the second CAD pattern 102. The scanning electron microscope 1 generates the image 200 of the first actual pattern 201 and the second actual pattern 202, which correspond to the first CAD pattern 101 and the second CAD pattern 102, and the pattern measuring device 5 acquires the image 200 from the scanning electron microscope 1.

[0032] The pattern measuring device 5 detects the first actual edge 201a and the second actual edge 202a on the image 200 corresponding to the first CAD edge 101a and the second CAD edge 102a using the edge detection parameters, and measures the distance L between the first actual edge 201a and the second actual edge 202a in the normal direction. This normal direction is a direction perpendicular to the extension line 105 (and the first CAD edge 101a) shown in FIG. 2.

[0033] According to this embodiment, even if the first actual edge 201a and the second actual edge 202a are not opposite each other, the pattern measuring device 5 can measure the distance L in the normal direction between the first actual edge 201a and the second actual edge 202a based on pattern information (relative positions between edges, layer numbers, etc.) regarding the first CAD pattern 101 and the second CAD pattern 102, as described with reference to Figure 2.

[0034] Next, an embodiment will be described in which the first actual edge 201a and the second actual edge 202a on the image 200 are detected using edge detection parameters. Since the first actual edge 201a and the second actual edge 202a are detected according to the same edge detection method (algorithm), the detection of the first actual edge 201a will be described below.

[0035] The edge detection parameters include a peak search range and a bottom search range of the intensity profile of the first real pattern 201, and an edge detection threshold on the intensity profile. In this embodiment, the edge detection parameters further include the number of multiple intensity profiles of the first real pattern 201 used to create the intensity profile of the first real pattern 201. The intensity profile of the first real pattern 201 in this embodiment is an average of the multiple intensity profiles.

[0036] FIG. 4 is a diagram illustrating one embodiment of a process for detecting the first actual edge 201a of the first actual pattern 201. The pattern measuring device 5 creates a plurality of luminance profiles 300 on a plurality of edge search lines SR1 to SR5, including an edge search line SR3 perpendicular to the first actual edge 201a. The edge search line SR3 is located at the center of the plurality of edge search lines SR1 to SR5. The plurality of luminance profiles 300 represent the distribution of luminance values ​​of pixels on the plurality of search lines SR1 to SR5 perpendicular to the first actual edge 201a. The pattern measuring device 5 integrates the plurality of luminance profiles 300 and divides the obtained integrated profile by the number of the plurality of luminance profiles 300 to create an average luminance profile. This average luminance profile is the luminance profile on the edge search line SR3.

[0037] The number of intensity profiles 300 used to create the average intensity profile is one of the edge detection parameters. In FIG. 4, five intensity profiles 300 are used. However, the number of intensity profiles 300 is not limited to this embodiment. In one embodiment, the number of intensity profiles 300, which is one of the edge detection parameters, may be one. In this case, the intensity profile on the edge search line SR3 is used as is, and an average intensity profile is not created.

[0038] Next, the pattern measuring device 5 determines a peak search range RA1 and a bottom search range RA2 of the brightness profile on the edge search line SR3. The peak search range RA1 defines the range for searching for a peak point P on the brightness profile, and the bottom search range RA2 defines the range for searching for a bottom point B on the brightness profile.

[0039] As shown in FIG. 4, the peak search range RA1 is determined based on the position C of the first CAD edge 101a of the first CAD pattern 101. Specifically, the peak search range RA1 is a range of a predetermined width centered on the position C of the first CAD edge 101a. The pattern measuring device 5 determines a peak point P, which is the point on the luminance profile with the highest luminance value within the peak search range RA1. The bottom search range RA2 is a range of a predetermined width with the position of the peak point P as its lower limit. The pattern measuring device 5 determines a bottom point B, which is the point on the luminance profile with the lowest luminance value within the bottom search range RA2.

[0040] The pattern measuring device 5 reads out from the storage device 5a a predetermined edge detection threshold value for the first layer to which the first CAD pattern 101 belongs, and determines the position of the first actual edge 201a on the edge search line SR3 using the edge detection threshold value. That is, as shown in FIG. 4, the pattern measuring device 5 determines the position of the intersection E between the brightness profile and the edge detection threshold value, and sets the position of the intersection E as the position of the first actual edge 201a on the edge search line SR3. The pattern measuring device 5 determines the overall position of the first actual edge 201a by repeating the same operation while changing the positions of the edge search lines SR1 to SR5 on the first actual edge 201a. The pattern measuring device 5 similarly detects the second actual edge 202a of the second actual pattern 202 shown in FIG. 3.

[0041] 2, the pattern measurement device 5 acquires information about the layers to which the first real pattern 201 and the second real pattern 202 belong, and is therefore able to use an optimum edge detection threshold value that is predetermined for each layer. Specifically, a first edge detection threshold value is used to detect the first real edge 201a that belongs to the first layer, and a second edge detection threshold value is used to detect the second real edge 202a that belongs to the second layer. Therefore, the pattern measurement device 5 can accurately detect the first real edge 201a and the second real edge 202a, and as a result, can accurately measure the distance L between the first real edge 201a and the second real edge 202a.

[0042] 5 is a schematic diagram showing an example of an image in which a third real pattern 203 exists between a first real pattern 201 and a second real pattern 202. The third real pattern 203 is a pattern that is not a measurement target. The third real pattern 203 is, for example, a pattern of a third layer that exists below a second layer. The existence of such a third real pattern 203 can become noise in edge detection of the first real pattern 201 and the second real pattern 202.

[0043] 5, the luminance profile BP1 on the search line SR11 includes not only the luminance of the first real pattern 201 but also the luminance of the third real pattern 203. The luminance profile BP2 on the search line SR12 also includes not only the luminance of the second real pattern 202 but also the luminance of the third real pattern 203. The luminance of the third real pattern 203 included in the luminance profiles BP1 and BP2 may hinder accurate detection of the edges of the first real pattern 201 and the second real pattern 202.

[0044] Therefore, the pattern measuring device 5 limits the search ranges for the edges 201a and 202a of the first actual pattern 201 and the second actual pattern 202 based on the pattern information of the corresponding first CAD pattern 101 and the pattern information of the corresponding second CAD pattern 102. Specifically, the pattern measuring device 5 limits the lengths of each of the search lines SR1 to SR5 described with reference to FIG.

[0045] The pattern measuring device 5 acquires position information of the third CAD pattern corresponding to the third real pattern 203 during the pattern search operation described with reference to FIG. 2. The pattern measuring device 5 limits the search range for the edge 201a of the first real pattern 201 based on the position information of the first CAD pattern 101 and the position information of the third CAD pattern. Similarly, the pattern measuring device 5 limits the edge search range for the edge 202a of the second real pattern 202 based on the position information of the second CAD pattern 102 and the position information of the third CAD pattern. As a result, the intensity profiles BP1 and BP2 do not include the intensity of the third real pattern 203. Therefore, the pattern measuring device 5 can accurately detect the edges 201a and 202a of the first real pattern 201 and the second real pattern 202.

[0046] In the embodiment described with reference to FIGS. 2 to 5, the first CAD pattern 101 (first actual pattern 201) and the second CAD pattern 102 (second actual pattern 202) belong to different layers. However, in one embodiment, the first CAD pattern 101 (first actual pattern 201) and the second CAD pattern 102 (second actual pattern 202) may belong to the same layer. For example, in FIG. 6, multiple CAD patterns 301 and 302 belonging to the same layer are arranged alternately. Even in this case, the pattern measurement device 5 can determine the CAD edges 301a and 302a to be measured according to the pattern search operation described with reference to FIG. 2 and accurately measure the distance between the corresponding actual edges on the image.

[0047] Typically, a large number of measurement points for the distance between patterns are set on a single workpiece. Therefore, to facilitate management of the distance measurement results, in the embodiment described below, the pattern measurement device 5 classifies the set of actual edges to be measured as either line, space, or pitch according to their attributes, and outputs the attribute (line, space, or pitch) along with the distance measurement value. This embodiment will be described in detail below.

[0048] As shown in FIG. 7 , the pattern measurement device 5 assigns orientation information to the CAD edges constituting each of the first CAD pattern 101 and the second CAD pattern 102. The orientation information is assigned to the CAD edges according to a predetermined rule. In one embodiment, the predetermined rule is to assign a clockwise or counterclockwise orientation. For example, as shown by the arrows in FIG. 7 , the pattern measurement device 5 assigns a clockwise orientation to the CAD edges constituting each of the first CAD pattern 101 and the second CAD pattern 102. In one embodiment, the predetermined rule is to assign a clockwise or counterclockwise orientation depending on the type of CAD pattern. For example, the CAD edges of a CAD island pattern are assigned a clockwise orientation, and the CAD edges of a CAD hole pattern are assigned a counterclockwise orientation.

[0049] The pattern measuring device 5 determines an attribute of line, space, or pitch based on the combination of the orientations of the two CAD edges to be measured for distance, and assigns the attribute to a pair of two actual edges corresponding to the two CAD edges.

[0050] 8 is a diagram illustrating the attributes of line, space, and pitch. A line attribute is used when the orientations of two CAD edges, the distance of which is to be measured, are opposite. That is, when the orientation of a CAD edge of a first CAD pattern 101 is a first orientation and the orientation of a CAD edge of a second CAD pattern 102 is a second orientation opposite to the first orientation, the pattern measuring device 5 assigns a line attribute to a pair of two actual edges corresponding to these two CAD edges.

[0051] A space is an attribute when the orientations of two CAD edges, which are the object of distance measurement, are opposite to each other and are opposite to the attribute of a line. That is, when the orientation of the CAD edge of the first CAD pattern 101 is a second orientation and the orientation of the CAD edge of the second CAD pattern 102 is a first orientation, the pattern measuring device 5 assigns a space attribute to the pair of two actual edges corresponding to these two CAD edges.

[0052] The pitch is an attribute when the orientations of two CAD edges, which are the object of distance measurement, are the same. That is, when the orientations of the CAD edges of the first CAD pattern 101 and the second CAD pattern 102 are both the first orientation or the second orientation, the pattern measuring device 5 assigns the attribute of pitch to a pair of two actual edges corresponding to these two CAD edges.

[0053] The pattern measurement device 5 associates the attributes of a pair of two actual edges to be measured with the measured value of the distance between these actual edges. The measured value of the distance between the actual edges is stored in the storage device 5a together with the associated attributes.

[0054] 9 is a schematic diagram showing an example of an image of real patterns formed in three layers. In the example shown in FIG. 9, a first real pattern 401, a second real pattern 402, and a third real pattern 403 appear in an image 400. The first real pattern 401 is located in the first layer, the second real pattern 402 is located in the second layer, and the third real pattern 403 is located in the third layer. The first real pattern 401 and the third real pattern 403 are non-transparent patterns made of a non-transparent material that does not allow the electron beam to pass through, and the second real pattern 402 is a transparent pattern made of a transparent material that allows the electron beam to pass through.

[0055] Whether a pattern transmits an electron beam or not is determined by the material that constitutes the pattern, the thickness of the pattern, and the acceleration voltage of the electron beam. For example, metals are difficult for electron beams to transmit, while polysilicon and insulating materials (such as SiO2) transmit electron beams. The pattern measurement device 5 designates multiple CAD patterns included in the design data as either transparent or non-transparent patterns based on factors such as the material that constitutes the pattern, the thickness of the pattern, and the acceleration voltage of the electron beam.

[0056] 9, the CAD patterns corresponding to the first actual pattern 401 and the third actual pattern 403 are designated as non-transparent patterns, and the CAD pattern corresponding to the second actual pattern 402 is designated as a transparent pattern. In another example, the first CAD pattern 101 shown in FIG. 3 is designated as a non-transparent pattern, and the second CAD pattern 102 is designated as a transparent pattern.

[0057] To measure the distance between real patterns, the real patterns must appear in the image. Whether or not the real patterns to be measured for distance appear in the image can be determined based on the position, area, and whether the CAD patterns on each layer are transparent or opaque.

[0058] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0059] 1. Scanning Electron Microscope 5. Operation control section 15 Electron Gun 16 focusing lens 17X deflector 18 Y deflector 20 Objective Lens 26 Electron Detector 31 Stages 101 First CAD pattern 101a 1st CAD edge 102 Second CAD pattern 102a 2nd CAD edge 105 Extension line 200 images 201 First real pattern 201a First real edge 202 Second Actual Pattern 202a Second real edge 301,302 CAD patterns 400 images 401 First real pattern 402 Second real pattern 403 Third Real Pattern SR1~SR5,SR11,SR12 Edge search lines RA1 Peak search range RA2 Bottom search range

Claims

1. A pattern measurement method for measuring distances between multiple patterns on an image, comprising: connecting an extension line of a predetermined length to an end of the first CAD edge of the first CAD pattern; determining a second CAD pattern having a second CAD edge that exists within a predetermined search range in a normal direction from the extension line; acquiring first pattern information including a layer number to which the first CAD pattern belongs and second pattern information including a layer number to which the second CAD pattern belongs from design data; detecting a first actual edge and a second actual edge on the image corresponding to the first CAD edge and the second CAD edge using edge detection parameters; a pattern measuring method for measuring a distance between the first actual edge and the second actual edge in the normal direction;

2. 2. The pattern measuring method according to claim 1, wherein a layer to which the second CAD pattern belongs is different from a layer to which the first CAD pattern belongs.

3. 2. The pattern measuring method according to claim 1, wherein the layer to which the second CAD pattern belongs is the same as the layer to which the first CAD pattern belongs.

4. 3. The pattern measuring method according to claim 2, wherein the edge detection parameters include a first edge detection parameter predetermined for a layer to which the first CAD pattern belongs, and a second edge detection parameter predetermined for a layer to which the second CAD pattern belongs.

5. The pattern measurement method according to claim 1 , wherein the edge detection parameters include a peak search range and a bottom search range of a luminance profile of the actual pattern, and an edge detection threshold on the luminance profile.

6. providing orientation information to a plurality of CAD edges constituting each of the first CAD pattern and the second CAD pattern in accordance with a predetermined rule; 2. The pattern measurement method according to claim 1, further comprising assigning an attribute of one of line, space, or pitch to the pair of the first actual edge and the second actual edge based on the orientation of the first CAD edge and the orientation of the second CAD edge indicated in the orientation information.

7. if the orientation of the first CAD edge is a first orientation and the orientation of the second CAD edge is a second orientation opposite to the first orientation, assigning a line attribute to the pair of the first actual edge and the second actual edge; when the orientation of the first CAD edge is the second orientation and the orientation of the second CAD edge is the first orientation, assigning a space attribute to the pair of the first actual edge and the second actual edge; 7. The pattern measurement method according to claim 6, wherein when the orientation of the first CAD edge and the orientation of the second CAD edge are both the first orientation or the second orientation, an attribute of pitch is assigned to the pair of the first actual edge and the second actual edge.

8. the layer to which the second CAD pattern belongs is below the layer to which the first CAD pattern belongs; 3. The pattern measuring method according to claim 2, further comprising specifying each of the first CAD pattern and the second CAD pattern as either a transparent pattern or a non-transparent pattern.

9. A pattern measurement device for measuring distances between a plurality of patterns on an image, a storage device storing programs and design data; a computing device that executes operations in accordance with instructions included in the program; The program connecting an extension line of a predetermined length to an end of the first CAD edge of the first CAD pattern; determining a second CAD pattern having a second CAD edge that exists within a predetermined search range in a normal direction from the extension line; acquiring first pattern information including a layer number to which the first CAD pattern belongs and second pattern information including a layer number to which a second CAD pattern belongs from the design data; detecting a first actual edge and a second actual edge on the image corresponding to the first CAD edge and the second CAD edge using edge detection parameters; a pattern measuring device configured to cause the arithmetic unit to perform an operation of measuring a distance between the first actual edge and the second actual edge in the normal direction;

10. 10. The pattern measuring device according to claim 9, wherein a layer to which the second CAD pattern belongs is different from a layer to which the first CAD pattern belongs.

11. 10. The pattern measuring device according to claim 9, wherein the layer to which the second CAD pattern belongs is the same as the layer to which the first CAD pattern belongs.

12. 11. The pattern measuring device according to claim 10, wherein the edge detection parameters include a first edge detection parameter predetermined for a layer to which the first CAD pattern belongs, and a second edge detection parameter predetermined for a layer to which the second CAD pattern belongs.

13. 10. The pattern measuring device according to claim 9, wherein the edge detection parameters include a peak search range and a bottom search range of a luminance profile of the actual pattern, and an edge detection threshold value on the luminance profile.

14. The program providing orientation information to a plurality of CAD edges constituting each of the first CAD pattern and the second CAD pattern in accordance with a predetermined rule; 10. The pattern measuring device according to claim 9, wherein the computing device is configured to perform an operation of assigning an attribute of one of line, space, or pitch to a pair of the first actual edge and the second actual edge based on the orientation of the first CAD edge and the orientation of the second CAD edge indicated in the orientation information.

15. The program if the orientation of the first CAD edge is a first orientation and the orientation of the second CAD edge is a second orientation opposite to the first orientation, assigning a line attribute to the pair of the first actual edge and the second actual edge; when the orientation of the first CAD edge is the second orientation and the orientation of the second CAD edge is the first orientation, assigning a space attribute to the pair of the first actual edge and the second actual edge; 15. The pattern measuring device according to claim 14, wherein, when both the orientation of the first CAD edge and the orientation of the second CAD edge are the first orientation or the second orientation, the calculation device is configured to perform an operation of assigning a pitch attribute to a pair of the first actual edge and the second actual edge.

16. the layer to which the second CAD pattern belongs is below the layer to which the first CAD pattern belongs; 11. The pattern measuring device according to claim 10, wherein the program is configured to cause the arithmetic unit to execute an operation of designating each of the first CAD pattern and the second CAD pattern as either a transparent pattern or a non-transparent pattern.

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