Pattern position measurement method

Abstract

This invention provides a pattern position measurement method that can shorten the measurement time. [Solution] The method comprises the steps of: shifting a group of patterns, which are obtained by dividing a plurality of patterns formed on a substrate to be measured, at a reference position within the measurement field of view, sequentially measuring the position of each pattern at the reference position, and calculating the amount of deviation of the measured position of each pattern from the reference position; arranging a group of patterns at one of a plurality of design positions, which are part of a plurality of design positions within the measurement field of view and correspond to a group of patterns, and sequentially shifting the group of patterns to the other group of design positions, while repeatedly simultaneously measuring the position of each pattern in the group, and calculating the amount of deviation of the measured position of each pattern from the plurality of design positions; and calculating a first difference between the amount of deviation of the measured position of each pattern from the reference position and the amount of deviation of the measured position of each pattern from the plurality of design positions.

Description

Technical Field

[0001] The present invention relates to a pattern position measurement method.

Background Art

[0002] In recent years, with the high integration of LSIs, the circuit line width of semiconductor devices has been further miniaturized. In order to manufacture an exposure mask (also referred to as a reticle) used for forming a fine circuit pattern, an electron beam (EB: Electron beam) lithography technique having excellent resolution is used.

[0003] With the recent miniaturization of patterns, higher drawing accuracy has been required for electron beam lithography apparatuses. For this reason, the number of evaluation items (i.e., the number of measurement points) in the performance evaluation of the lithography apparatus has increased, and the measurement time required for performance evaluation has become very long. Since it is inevitable that the number of evaluation items will further increase as the accuracy increases, shortening the measurement time for each evaluation item is desired.

[0004] In performance evaluation, a pattern to be evaluated is drawn on a substrate, and the position of the drawn pattern is measured with a measuring device to evaluate the performance of the conditions when the pattern is drawn. Conventionally, a plurality of patterns drawn on the substrate under the conditions to be evaluated are sequentially arranged at the center of the measurement field of the measuring device, and the position of each pattern is measured at the center of the measurement field. However, when many patterns are drawn on one substrate, if the patterns are measured one by one with the measuring device, the measurement time becomes significantly long. For this reason, shortening the time by simultaneously measuring patterns at multiple points within the same field has been studied. However, when measuring multiple points simultaneously, a lens distortion error of the measuring device occurs. It becomes difficult to measure the accurate pattern position due to such distortion error.

[0005] Here, Patent Document 1 discloses a technique for correcting the pattern measurement position using the measured lens distortion error after measuring the lens distortion error. According to the technique described in Patent Document 1, it is possible to accurately measure the pattern position because the lens distortion error can be corrected. However, the technique described in Patent Document 1 is time-consuming to measure the lens distortion error, making it difficult to shorten the measurement time for the pattern position. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-215269 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide a pattern position measurement method that can shorten the measurement time. [Means for solving the problem]

[0008] A pattern position measurement method according to one aspect of the present invention comprises the steps of sequentially measuring the position of each pattern at a reference position while shifting a group of patterns, which are obtained by dividing a plurality of patterns formed on a substrate to be measured, at a reference position within a measurement field of view, and calculating the amount of deviation of the measured position of each pattern from the reference position. The method further comprises the steps of arranging a group of patterns at one of a plurality of design positions, which are part of a plurality of design positions within a measurement field of view and correspond to a group of patterns, and repeatedly simultaneously measuring the position of each pattern in the group while sequentially shifting the group of patterns to another group of design positions, and calculating the amount of deviation of the measured position of each pattern from the plurality of design positions. The method further comprises the steps of calculating a first difference between the amount of deviation of the measured position of each pattern from the reference position and the amount of deviation of the measured position of each pattern from the plurality of design positions.

[0009] In the pattern position measurement method described above, a group of patterns may be a row of adjacent patterns.

[0010] The pattern position measurement method described above may further include the steps of: simultaneously measuring the positions of multiple patterns while multiple patterns formed on a substrate to be measured are arranged within the measurement field of view, calculating the amount of deviation of the measured positions of the multiple patterns from the design positions of the multiple patterns, and calculating a second difference which is the difference between the amount of deviation of the measured positions of the multiple patterns and the first difference.

[0011] In the pattern position measurement method described above, multiple patterns are formed on the substrate to be measured by etching using a resist pattern drawn with a charged particle beam as a mask, and the drawing conditions for forming the multiple patterns may differ for each of them.

[0012] In the pattern position measurement method described above, the drawing conditions may be the focus or dose amount of the charged particle beam. [Effects of the Invention]

[0013] According to the present invention, the measurement time can be shortened. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows an example configuration of a position measuring device that can be used in the pattern position measuring method according to this embodiment. [Figure 2] This flowchart shows the pattern position measurement method according to this embodiment. [Figure 3] This figure shows the pattern position measurement method according to this embodiment, including the step of simultaneous measurement of multiple points and the step of calculating the first positional displacement amount A. [Figure 4] This figure shows the sequential measurement process for a single point within the field of view (FOV) in the pattern position measurement method according to this embodiment. [Figure 5]In the pattern position measurement method according to this embodiment, it is a diagram showing a simultaneous measurement process for a row at a plurality of points within the FOV. [Figure 6] It is a diagram showing a pattern position measurement method according to a comparative example. [Figure 7] In the pattern position measurement method according to this embodiment, it is a diagram showing a data correction process. [Figure 8] It is a diagram showing a configuration example of a drawing device according to this embodiment. [Figure 9] It is a diagram showing an operation example of a drawing device according to this embodiment. [Figure 10] It is a diagram showing a pattern position measurement method according to a first modification example of this embodiment. [Figure 11] It is a diagram showing a pattern position measurement method according to a second modification example of this embodiment. [Figure 12] It is a diagram showing a pattern position measurement method according to a third modification example of this embodiment. [Figure 13] It is a flowchart showing a pattern position measurement method according to a fourth modification example of this embodiment. [Figure 14] It is a diagram showing a pattern position measurement method according to a fourth modification example of this embodiment. [Figure 15] It is a diagram showing a pattern position measurement method according to a fifth modification example of this embodiment.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments do not limit the present invention. In the drawings referred to in the embodiments, the same parts or parts having the same or similar functions are denoted by the same reference numerals or similar reference numerals, and the repeated description thereof will be omitted.

[0016] Figure 1 shows an example configuration of a position measuring device 300 that can be used in the pattern position measuring method according to this embodiment. As shown in Figure 1, the position measuring device 300 includes an XY stage 302, a control computer unit 310, a memory 312, an external interface (I / F) circuit 314, a lighting device 320, a camera 331, a drive circuit 332, and a storage device 340 such as a magnetic disk drive.

[0017] The control computer unit 310, memory 312, external I / F circuit 314, lighting device 320, camera 331, drive circuit 332, and storage device 340 are connected to each other via a bus (not shown). A sample 400 (i.e., the substrate to be measured) with a pattern drawn on it is placed on the XY stage 302. The sample 400 includes exposure masks and silicon wafers for manufacturing semiconductor devices, on which multiple patterns are formed. The sample 400 further includes a substrate on which multiple evaluation patterns are formed for evaluating various drawing conditions. The sample 400 also includes a substrate on which multiple patterns have been drawn using an electron beam and then developed; in other words, a substrate on which resist patterns constituting multiple patterns have been formed. The sample 400 also includes a substrate on which a film such as a light-shielding film in the underlying layer has been etched using such resist patterns as a mask, thereby forming multiple film patterns such as light-shielding films constituting multiple patterns. In other words, multiple patterns are formed on the sample 400 by etching using the resist patterns drawn using an electron beam as a mask. The XY stage 302 is controlled by the drive circuit 332 to be movable in the horizontal X and Y directions. The camera 331 is equipped with a lens 304 and a photodetector array 306, which form an imaging optical system for capturing the image.

[0018] The control computer unit 310 comprises a measuring unit 50, a first positional displacement amount calculation unit 51, a second positional displacement amount calculation unit 52, a third positional displacement amount calculation unit 53, a fourth positional displacement amount calculation unit 54, a correction unit 56, and a control unit 58. The measuring unit 50, the first positional displacement amount calculation unit 51, the second positional displacement amount calculation unit 52, the third positional displacement amount calculation unit 53, the fourth positional displacement amount calculation unit 54, the correction unit 56, and the control unit 58 may be composed of software (i.e., programs), hardware such as electronic circuits, or a combination thereof. Data input into the control computer unit 310 and the results calculated by the control computer unit 310 are stored in the memory 312 each time. If at least one of the measurement unit 50, positional displacement calculation units 51-54, correction unit 56, and control unit 58 is configured as software, a computer such as a CPU or GPU is provided to execute the software and realize the functions of the corresponding components 50-54, 56, and 58. Note that the positional displacement calculation units 51-54 and the correction unit 56 of the control computer unit 310 do not necessarily need to be located within the position measuring device 300; calculation processing may be performed outside the position measuring device 300.

[0019] Next, a pattern position measurement method using the position measuring device 300 will be described. Note that the pattern position measurement method described below may be implemented using a configuration other than that shown in Figure 1.

[0020] Figure 2 is a flowchart showing the pattern position measurement method according to this embodiment. As shown in Figure 2, first, the measurement unit 50 performs simultaneous measurement of multiple points (step S1). Simultaneous measurement of multiple points means that, with multiple patterns to be measured formed on the sample 400 (i.e., the substrate to be measured) arranged within the measurement field of view (FOV), the positions of each of the multiple patterns arranged within the measurement field of view are measured simultaneously.

[0021] Figure 3 shows the process of simultaneous measurement of multiple points and the calculation of the first positional displacement A in the pattern position measurement method according to this embodiment. In simultaneous measurement of multiple points, first, the sample 400 is placed on the XY stage 302. After the sample 400 is placed on the XY stage 302, the drive circuit 332 moves the XY stage 302 so that the multiple patterns 62 to be measured are located within the field of view 60 of the camera 331 (i.e., within the measurement field of view), as shown in Figure 3. In the example shown in Figure 3, a total of 49 rectangular patterns 62 are arranged in 7 rows × 7 columns (i.e., 7 in the x direction and 7 in the y direction) as the multiple patterns 62 to be measured. In the example shown in Figure 3, the size of each pattern 62 is the same, and the pitch in the x direction and the pitch in the y direction are uniform. Note that the x direction and y direction in Figure 3 are directions defined in the coordinate system of the camera 331. The x direction in Figure 3 corresponds to the X direction of the XY stage 302. The y-direction in Figure 3 corresponds to the Y-direction of the XY stage 302. The drawing conditions for the multiple patterns 62 are different from each other. By measuring the positions of the multiple patterns 62 with different drawing conditions, the measured positions can be used to evaluate the drawing conditions. Details of the drawing conditions will be described later.

[0022] After multiple patterns 62 are positioned within the field of view 60, the illumination device 320 illuminates the pattern-forming surface of the sample 400. With the pattern-forming surface illuminated, the camera 331 images the multiple patterns 62 arranged within the field of view 60. The camera 331 outputs the image data (e.g., waveform data) of the captured field of view 60 to the measurement unit 50.

[0023] The measuring unit 50 simultaneously measures the positions of multiple patterns 62 using image data within the field of view 60 input from the camera 331. The measuring unit 50 identifies each position of a pattern 62, for example, using a representative position of the pattern. Suitable representative positions include, for example, the center of the pattern's area, its centroid, and any of the corner positions (up, down, left, or right).

[0024] After simultaneous measurement of multiple points is performed, as shown in Figure 2, the first positional displacement amount calculation unit 51 calculates the first positional displacement amount A (step S2). The first positional displacement amount A is the amount of displacement of the measurement positions of multiple patterns 62 measured by simultaneous measurement of multiple points from multiple design positions within a preset field of view 60. The multiple design positions are design positions corresponding to each of the multiple patterns 62. The multiple design positions may be multiple positions set within the field of view 60 to correspond to the design positions of the multiple patterns 62. For example, the multiple design positions may be multiple positions set at equal intervals in the x and y directions within the field of view 60. In calculating the first positional displacement amount A, the first positional displacement amount calculation unit 51 acquires the multiple design positions within the field of view 60. The first positional displacement amount calculation unit 51 may acquire the information of the multiple design positions stored in the memory 312, for example. After acquiring multiple design positions, the first positional displacement calculation unit 51 calculates the first positional displacement A for each pattern 62 by calculating the amount of displacement of the measurement position of each pattern 62 from the corresponding design position among the acquired multiple design positions. In the example shown in Figure 3, the multiple design positions within the field of view 60 are shown as the center points (i.e., intersections) of the cross marks. Also in the example shown in Figure 3, the measurement positions of each pattern 62 are shown as grid points of a mesh-like line. The amount of displacement of the corresponding grid point from the center point of each cross mark corresponds to the first positional displacement A for each pattern 62. After calculating the first positional displacement A, as shown in Figure 2, the first positional displacement calculation unit 51 creates map-type data (hereinafter also called the first positional displacement A map) to which the first positional displacement A is associated for each design position, and records the created first positional displacement A map in the storage device 340. Furthermore, the data format of the first positional displacement amount calculation unit 51 is not limited, as long as it records the first positional displacement amount A of each pattern 62 in the storage device 340 in a readable format.

[0025] Here, when the camera 331 captures images of multiple patterns 62 placed within the field of view 60, distortion occurs in the captured images due to the lens 304. Therefore, the first positional displacement A includes a lens distortion error that depends on the design position within the field of view 60. In this embodiment, in order to correct the lens distortion error, the lens distortion error is first measured. Hereinafter, the lens distortion error will also be referred to as the distortion amount.

[0026] To measure the amount of distortion, as shown in Figure 2, the measurement unit 50 first performs a sequential measurement in a row at one point within the FOV (step S3). A sequential measurement in a row at one point within the FOV means sequentially measuring the position of each pattern at a reference position (i.e., one point) within the field of view 60, while shifting each pattern in a row of adjacent pattern groups, which are obtained by dividing multiple patterns formed on the sample 400, at the reference position. The reference position is, for example, the center position of the field of view 60. The reference position can also be a position other than the center position of the field of view 60. A row of adjacent pattern groups (hereinafter also referred to as a row of pattern groups) is, for example, a group of patterns from among multiple patterns 62 that have been measured simultaneously at multiple points. If the pitch (i.e., period) is the same as that of the patterns 62 that have been measured simultaneously at multiple points, the row of pattern groups may be dedicated patterns formed separately from the patterns 62 for the purpose of calculating the amount of distortion.

[0027] Figure 4 shows the sequential measurement process for a single row at one point within the field of view (FOV) in the pattern position measurement method according to this embodiment. In sequential measurement, first, the measurement unit 50 selects a row of patterns 63 to be used for sequential measurement from among the patterns formed on the sample 400. In the example shown in Figure 4, of the 7 rows x 7 columns of patterns 62, the seven patterns 62 in the central fourth column, including the pattern 62 positioned at the center of the field of view 60 as the reference position P, are selected as the row of patterns 63. In the example shown in Figure 4, the reference position P corresponds to the central design position among multiple design positions within the field of view 60 indicated by a rectangular dashed line. When the seven patterns 62 in the fourth column are selected as the row of patterns 63, sequential measurement can be performed by moving the row of patterns 63 only in the y direction by moving the XY stage 302. However, a group of patterns 62 other than the seven patterns 62 in the fourth column may also be selected as the row of patterns 63.

[0028] After a row of pattern groups 63 is selected, the drive circuit 332 moves the XY stage 302 so that the first pattern 62 to be measured from the row of pattern groups 63 is located at the reference position P (step S31). In the example shown in Figure 4, the first pattern 62 to be measured is the pattern 62 located at the y-end of the row of pattern groups 63. When the first pattern 62 to be measured is located at the reference position P, the illumination device 320 illuminates the pattern-forming surface of the sample 400. The camera 331 also sets an ROI (region of interest) at the reference position P and images multiple patterns 62 arranged within the field of view 60. In the example shown in Figure 4, the blacked-out patterns 62 represent the patterns 62 for which an ROI has been set (the same applies hereafter). In Figure 4, the illustration of patterns 62 other than the row of pattern groups 63 is omitted. The camera 331 outputs the image data of the captured images within the field of view 60 to the measurement unit 50. The measurement unit 50 measures the position of the first pattern 62 to be measured, which is located at the reference position P where the ROI is set, based on the image data input from the camera 331. In other words, the measurement unit 50 performs the first position measurement of a row of pattern group 63 at the reference position P, which is a single point within the field of view 60.

[0029] After the position of the first pattern 62 to be measured is determined, the drive circuit 332 moves the XY stage 302 so that the second pattern 62 to be measured from the row of pattern group 63 is located at the reference position P (step S32). In the example shown in Figure 4, the second pattern 62 to be measured is the second pattern 62 from the y-direction end of the row of pattern group 63. When the second pattern 62 to be measured is located at the reference position P, the illumination device 320 illuminates the pattern-forming surface of the sample 400. The camera 331 also maintains an ROI at the reference position P and images the multiple patterns 62 arranged within the field of view 60. The camera 331 outputs image data of the captured images within the field of view 60 to the measurement unit 50. Based on the image data input from the camera 331, the measurement unit 50 measures the position of the second pattern 62 to be measured, which is located at the reference position P where the ROI is set. In other words, the measuring unit 50 performs a second position measurement of the row of pattern group 63 at the reference position P.

[0030] Subsequently, the drive circuit 332 moves the XY stage 302 to position the row of patterns 63 one pattern 62 at a time at the reference position P (step S33). The measurement unit 50 measures the position of each pattern 62 positioned sequentially at the reference position P based on the image data of the captured image in the field of view 60 input from the camera 331. The measurement unit 50 repeats the measurement of the position of each pattern 62 of the row of patterns 63 at the reference position P until the seventh (i.e., last) pattern 62, which is located at the end of the row of patterns 63 in the -y direction (step S34). In this way, sequential measurement of each row is performed.

[0031] After a row-by-row sequential measurement is performed, the second positional displacement amount calculation unit 52 calculates the second positional displacement amount B, as shown in Figure 2 (step S4). The second positional displacement amount B is the amount of displacement of the measurement position of each pattern 62 in a row of pattern group 63 from the reference position P. That is, the second positional displacement amount B is the amount of displacement of the measurement position due to the row-by-row sequential measurement from the reference position P. The second positional displacement amount calculation unit 52 obtains the measurement position from the measurement unit 50 due to the row-by-row sequential measurement. After obtaining the measurement position due to the row-by-row sequential measurement, the second positional displacement amount calculation unit 52 calculates the second positional displacement amount B by calculating the difference in the measurement position due to the row-by-row sequential measurement from the reference position P. In the example shown in Figure 4, the second positional displacement amount B is represented as the amount of displacement of the corresponding grid point from the center point of a row of cross marks. The second positional displacement amount calculation unit 52 records the calculated second positional displacement amount B in the storage device 340.

[0032] When the reference position P is at the center of the field of view 60, the second positional displacement B is the displacement of the measurement position at the position with the minimum distortion. That is, when the reference position P is at the center of the field of view 60, the second positional displacement B is the displacement that depends on the drawing conditions of each pattern 62 in the row of pattern group 63. By subtracting this displacement that depends on the drawing conditions of each pattern 62 from the displacement of the measurement positions of the row of pattern group 63 at multiple points within the field of view 60, the amount of distortion can be calculated.

[0033] After the second positional displacement amount B is calculated, as shown in Figure 2, the measurement unit 50 performs a single-row simultaneous measurement at multiple points within the FOV (step S5). A single-row simultaneous measurement at multiple points within the FOV means placing a single-row pattern group 63 at one of the adjacent design position groups in a row, which are part of multiple design positions within the field of view 60 and correspond to one of the adjacent design position groups in a row that form a single-row pattern group 63, and then sequentially shifting the single-row pattern group 63 to other adjacent design position groups in a row, while repeatedly performing simultaneous measurements of the position of each pattern 62 in the single-row pattern group 63.

[0034] Figure 5 shows the process of simultaneous measurement of a single row at multiple points within the FOV in the pattern position measurement method according to this embodiment. In simultaneous measurement of a single row, first, the measurement unit 50 selects a group of adjacent design positions in a row (hereinafter also referred to as a single row of design positions) to be used for the first simultaneous measurement of a single row from among a plurality of design positions within the field of view 60. In the example shown in Figure 5, the group of design positions in the first column counting in the x direction is selected from among the 7 rows x 7 columns of design positions.

[0035] After the first row of design position groups is selected, the drive circuit 332 moves the XY stage 302 to simultaneously move a row of pattern groups 63 to the selected first row of design position groups (step S51). Once the row of pattern groups 63 is moved to the first row of design position groups, the illumination device 320 illuminates the pattern-forming surface of the sample 400. The camera 331 sets an ROI in the first row of design position groups and images multiple patterns 62 placed within the field of view 60. The camera 331 outputs image data of the captured images within the field of view 60 to the measurement unit 50. Based on the image data input from the camera 331, the measurement unit 50 simultaneously measures the position of each pattern 62 in the row of pattern groups 63 placed in the first row of design position groups where the ROI has been set. That is, the measurement unit 50 performs the first simultaneous measurement of a row at multiple points within the field of view 60 in the first row of design position groups.

[0036] After the first simultaneous measurement of a single row is performed, the measurement unit 50 selects a group of design positions in a row from among multiple design positions within the field of view 60 to be used for the second simultaneous measurement of a single row. In other words, the measurement unit 50 changes the selection of the group of design positions in a row. In the example shown in Figure 5, the group of design positions in the second column in the x-direction is selected from among the 7 rows x 7 columns of design positions.

[0037] After the second row of design positions is selected, the drive circuit 332 moves the XY stage 302 to simultaneously move a row of patterns 63 to the selected second row of design positions (step S52). Once the row of patterns 63 is moved to the second row of design positions, the illumination device 320 illuminates the pattern-forming surface of the sample 400. The camera 331 also moves the ROI to the second row of design positions and images multiple patterns 62 arranged within the field of view 60. The camera 331 outputs image data of the captured images within the field of view 60 to the measurement unit 50. Based on the image data input from the camera 331, the measurement unit 50 simultaneously measures the position of each pattern 62 in the row of patterns 63 arranged in the second row of design positions where the ROI is set. In other words, the measurement unit 50 performs a second simultaneous measurement of a row in the second row of design positions.

[0038] Subsequently, the measurement unit 50 changes the selection of a row of design position groups one row at a time in the x-direction. Each time the selection is changed, the drive circuit 332 moves the XY stage 302 and simultaneously moves a row of pattern groups 63 to the newly selected row of design position groups (step S53). Each time a row of pattern groups 63 is moved to a newly selected row of design position groups, the measurement unit 50 simultaneously measures the position of each pattern 62 in the row of pattern groups 63 based on the image data of the captured image in the field of view 60 input from the camera 331. The measurement unit 50 repeats the simultaneous measurement of each pattern position in a row of pattern groups 63 up to the seventh row of design position groups located at the end in the x-direction (step S54). In this way, simultaneous measurement of a row is performed.

[0039] After the simultaneous measurement of a single row is performed, the third positional displacement amount calculation unit 53 calculates the third positional displacement amount C, as shown in Figure 2 (step S6). The third positional displacement amount C is the amount of displacement of the measurement position of each pattern 62 of the row of pattern group 63 from multiple design positions within the field of view 60. In other words, the third positional displacement amount C is the amount of displacement of the measurement position due to the simultaneous measurement of a single row from multiple design positions within the field of view 60. The third positional displacement amount calculation unit 53 obtains the measurement position from the measurement unit 50 due to the simultaneous measurement of a single row. After obtaining the measurement position due to the simultaneous measurement of a single row, the third positional displacement amount calculation unit 53 calculates the third positional displacement amount C by calculating the difference between the measurement positions due to the simultaneous measurement of a single row from multiple design positions within the field of view 60. In the example shown in Figure 5, the third positional displacement amount C is represented as the amount of displacement of the corresponding grid point from the center point of the cross mark.

[0040] After calculating the third positional displacement amount C, as shown in Figure 2, the third positional displacement amount calculation unit 53 creates a map-format data (hereinafter also referred to as the third positional displacement amount C map) to which the third positional displacement amount C is associated for each design position, and records the created third positional displacement amount C map in the storage device 340. The data format of the third positional displacement amount calculation unit 53 is not limited as long as it records the third positional displacement amount C for each pattern 62 in a readable format in the storage device 340.

[0041] Here, the third positional displacement C is the sum of the displacement amount dependent on the drawing conditions of pattern 62 and the distortion amount, which is the displacement amount dependent on the design position. The second positional displacement B mentioned above is the displacement amount dependent on the drawing conditions of pattern 62. Therefore, to find the distortion amount, we just need to calculate the difference (C - B) between the second positional displacement B and the third positional displacement C.

[0042] After the third positional misalignment amount C is calculated, the fourth positional misalignment amount calculation unit 54 calculates the distortion amount (i.e., the fourth positional misalignment amount) D, as shown in Figures 2 and 5 (step S7). The distortion amount D is the difference (i.e., the first difference) between the amount of misalignment of the measurement position of each pattern 62 in a row of pattern groups 63 from the reference position P and the amount of misalignment of the measurement position of each pattern 62 in a row of pattern groups 63 from multiple design positions. In other words, the distortion amount D is the difference (C - B) between the second positional misalignment amount B and the third positional misalignment amount C. The fourth positional misalignment amount calculation unit 54 reads the second positional misalignment amount B and the third positional misalignment amount C map from the storage device 340. The fourth positional misalignment amount calculation unit 54 calculates the distortion amount D based on the read second positional misalignment amount B and the third positional misalignment amount C map.

[0043] After calculating the distortion amount D, as shown in Figure 2, the fourth positional displacement calculation unit 54 creates a map-format data (hereinafter also called the distortion amount D map) in which the distortion amount D is associated with each design position, and records the created distortion amount D map in the storage device 340. Note that the data format of the fourth positional displacement calculation unit 54 is not limited as long as it records the distortion amount D in the storage device 340 in a readable format.

[0044] Figure 6 shows a pattern position measurement method according to a comparative example. In the comparative example, one pattern 62 to be measured is sequentially moved to multiple design positions within the field of view 60, and the position of the pattern 62 is measured each time (steps S501 to S504). Then, the amount of distortion is calculated by calculating the amount of deviation of the measurement position relative to the design position for each design position (step S505). In the comparative example, the number of times the XY stage 302 is moved to move the pattern 62 (i.e., the number of measurements) is 49. In contrast, in the examples shown in Figures 4 and 5, the number of times the XY stage 302 is moved is 14 in total, consisting of 7 times for sequential measurement of one row and 7 times for simultaneous measurement of one row. Therefore, according to this embodiment, the number of times the XY stage 302 is moved can be reduced compared to the comparative example. When the number of patterns 62 in the field of view 60 is N in the x direction and N in the y direction, the number of times the XY stage 302 is moved can be reduced to 2 / N compared to the comparative example. By reducing the number of times the XY stage 302 is moved, the measurement time can be shortened.

[0045] Figure 7 shows the data correction process in the pattern position measurement method according to this embodiment. After the distortion amount D is calculated, the correction unit 56 performs data correction (step S8) as shown in Figures 2 and 7. In data correction, the correction unit 56 calculates the positional misalignment difference amount E (i.e., the second difference), which is the difference between the first positional misalignment amount A and the distortion amount D, based on the first positional misalignment amount A map and the distortion amount D map recorded in the storage device 340. After calculating the positional misalignment difference amount E, the correction unit 56 creates map-format data (hereinafter also called the positional misalignment difference amount E map) to which the positional misalignment difference amount E is associated for each design position, and records the created positional misalignment difference amount E map in the storage device 340. By calculating the positional misalignment difference amount E, the distortion error included in the first positional misalignment amount A can be corrected. By using the positional misalignment difference amount E with the distortion error corrected, the drawing conditions can be appropriately evaluated.

[0046] To evaluate different drawing conditions, the drawing conditions for forming the multiple patterns 62 described above are all different. Before explaining specific examples of drawing conditions, we will first describe the drawing device that draws the multiple patterns 62.

[0047] The following description explains the configuration of a lithography system using an electron beam as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam; it may also be a beam using charged particles such as an ion beam. Furthermore, the following description explains a multi-charged particle beam lithography system as an example of a lithography system, but a lithography system using a single beam may also be used.

[0048] Figure 8 shows an example of the configuration of a lithography apparatus according to this embodiment. In the example shown in Figure 8, the lithography apparatus 1 comprises a lithography unit 2 and a control unit 3. The lithography apparatus 1 is an example of a multi-charged particle beam lithography apparatus. The lithography unit 2 comprises an electron tube 4 and a lithography chamber 6. Inside the electron tube 4, an electron source 41 and, in order along the optical path of the electron beam 200 irradiated from the electron source 41, an illumination lens 42, an aperture member 43, a blanking plate 44, a reduction lens 45, a first deflector 46, a limiting aperture member 47, an objective lens 48, and a second deflector 49 are arranged.

[0049] The aperture member 43 has a matrix of openings 43A arranged in a vertical (Y direction) a row × a horizontal (X direction) b row (a, b ≥ 2) at a predetermined arrangement pitch. Each opening 43A is formed as a rectangle with the same dimensions and shape in a plan view. The shape of the openings 43A is not limited to rectangles; for example, it may be circular. In such an aperture member 43, an electron beam 200 is irradiated from the electron source 41 onto the entire opening 43A, and a portion of the electron beam 200 passes through each of the multiple openings 43A, thereby forming a multibeam. Although Figure 1 shows a multibeam with five beams 20a to 20e, an actual multibeam has multiple beam rows.

[0050] The blanking plate 44 has through holes formed in it to match the positions of each opening 43A of the aperture member 43. Each of these through holes is fitted with a pair of electrodes, or blankers. The multi-beam passing through each through hole is deflected by the voltage applied to the corresponding blanker. In this way, multiple blankers perform blanking deflection of the beam corresponding to each blanker from among the multi-beams that have passed through the multiple openings 43A of the aperture member.

[0051] An XY stage 61, which is movable in at least the XY direction, is placed inside the drawing chamber 6. A sample 29 (substrate) to be drawn, on which resist has been applied, is placed on the XY stage 61. The sample 29 includes exposure masks and silicon wafers for manufacturing semiconductor devices. The masks include mask blanks. The sample 29 includes the sample 400 shown in Figure 1, which is the substrate to be measured.

[0052] The first deflector 46 and the second deflector 49 are composed of multiple electrodes, such as 4 poles or 8 poles. Although Figure 8 shows only one DAC (Digital to Analog Converter) amplifier 34, 35 corresponding to the first deflector 46 and the second deflector 49, in reality, at least one DAC amplifier is connected to each electrode.

[0053] The control unit 3 comprises a control computer 31, a deflection control unit 32, a blanking amplifier 33, deflection amplifiers (DAC amplifiers) 34 and 35, a memory 37, and a storage device 38 such as a magnetic disk drive. The control computer 31, the deflection control unit 32, the memory 37, and the storage device 38 are connected to each other via a bus (not shown). The deflection control unit 32, the blanking amplifier 33, and the DAC amplifiers 34 and 35 are also connected to each other via a bus (not shown).

[0054] The blanking amplifier 33 is connected to the blanking plate 44. The DAC amplifier 34 is connected to the first deflector 46. The DAC amplifier 35 is connected to the second deflector 49. Digital control signals independent of the deflection control unit 32 are output to the blanking amplifier 33 and the DAC amplifiers 34 and 35.

[0055] The blanking amplifier 33 and DAC amplifiers 34 and 35, which receive digital signals, convert their respective digital signals into analog voltage signals, amplify them, and output them as deflection voltages to each deflector. In this way, each deflector receives a deflection voltage from the DAC amplifier connected to it. The electron beam is deflected by these deflection voltages.

[0056] As described above, the drawing device 1 is equipped with a first deflector 46 and a second deflector 49, each with 4 or 8 poles, surrounding the electron beam. Each is arranged in pairs (2 pairs in the case of 4 poles, and 4 pairs in the case of 8 poles) on either side of the electron beam. DAC amplifiers 34 and 35 are connected to each of the first and second deflectors 46 and 49, respectively. However, Figure 8 only shows one DAC amplifier each connected to the first and second deflectors 46 and 49, and the other DAC amplifiers are omitted from the illustration.

[0057] The memory device 38 receives and stores drawing data from an external source.

[0058] Next, the drawing operation of the drawing device 1 will be described. The electron beam 200 emitted from the electron source 41 illuminates the entire aperture member 43 almost vertically through the illumination lens 42. The electron beam 200 illuminates the region containing the multiple openings 43A provided in the aperture member 43.

[0059] Each portion of the electron beam 200 irradiated at the positions of the multiple apertures 43A passes through each of the multiple apertures 43A. This forms a multibeam including, for example, multiple rectangular electron beams 20a to 20e. The electron beams 20a to 20e pass through the corresponding blankers of the blanking plate 44. The blankers perform blanking deflection, which deflects the multibeams individually.

[0060] The multibeam, having passed through the blanking plate 44, is reduced by the reduction lens 45 and then proceeds toward the central hole formed in the limiting aperture member 47. Here, the multibeam, deflected by the blanking plate 44, is moved away from the central hole in the limiting aperture member 47 and is shielded by the limiting aperture member 47.

[0061] Meanwhile, the multi-beams that are not deflected by the blanking plate 44 pass through the hole in the center of the limiting aperture member 47. By turning the blanking plate 44 ON or OFF, blanking control is performed, and the ON / OFF status of the multi-beams is controlled.

[0062] In this way, the limiting aperture member 47 shields each beam that has been deflected by multiple blankers so that the multibeam is in the OFF state. Then, the multibeam that has passed through the limiting aperture member 47, formed from the time the multibeam is turned ON until it is turned OFF, forms the beam for one shot.

[0063] The multi-beams that have passed through the limiting aperture member 47 are focused by the objective lens 48 to form a pattern image with the desired reduction ratio. Furthermore, the second deflector 49 deflects each beam (the entire multi-beam) that has passed through the limiting aperture member 47 in the same direction, and irradiates each beam to its respective irradiation position on the sample 29.

[0064] Figure 9 shows an example of operation of the drawing apparatus 1 according to this embodiment. In Figure 9, the drawing area 291 of the sample 29 is virtually divided into multiple stripe areas 292 in a strip-like shape, for example, in the Y direction, by the beam array width.

[0065] In the drawing device 1, the drawing process is carried out for each stripe region 292. The XY stage 61 moves continuously, for example, in the -X direction, and the drawing of the first stripe region 292 is carried out in the X direction. After the drawing of the first stripe region 292 is completed, the drawing of the second stripe region 292 is carried out in the same way, or in the opposite direction. Thereafter, the drawing of the third and subsequent stripe regions 292 is carried out in the same way. When the XY stage 61 is moving continuously, the beam irradiation position is controlled by the second deflector 49 to follow the movement of the XY stage 61. Ideally, the multi-beams irradiated at one time will be aligned with a beam pitch obtained by multiplying the array pitch of the multiple openings 43A of the aperture member 43 by the desired reduction ratio described above.

[0066] In such a lithography device, the performance of the multibeam is evaluated. For example, in order to evaluate the dependence on focus and dose, the lithography device 1 draws multiple patterns 62 by setting different focus and dose amounts.

[0067] By measuring the positions of multiple patterns 62 drawn under these different drawing conditions using the pattern position measurement method described above, each drawing condition can be quickly and appropriately evaluated based on the measured position.

[0068] As described above, in this embodiment, a group of patterns 63, which are obtained by dividing a plurality of patterns 62 formed on the substrate 400 to be measured, are shifted at a reference position P within the measurement field of view 60, and the position of each pattern 62 is sequentially measured at the reference position P. Then, the amount of deviation B of the measurement position of each pattern 62 from the reference position P is calculated. In addition, a group of patterns 63 is placed at one of a plurality of design positions that are part of a plurality of design positions within the measurement field of view 60 and correspond to a group of patterns 63, and the simultaneous measurement of the position of each pattern 62 of the group of patterns 63 is repeated while sequentially shifting the group of patterns 63 to the other group of design positions. Then, the amount of deviation C of the measurement position of each pattern 62 from the plurality of design positions is calculated. Furthermore, the amount of distortion D is calculated by calculating the first difference between the amount of deviation B of the measurement position of each pattern 62 from the reference position and the amount of deviation C of the measurement position of each pattern 62 from the plurality of design positions.

[0069] This allows for a reduction in the measurement time of the distortion amount D, thus shortening the measurement time of the pattern position while maintaining high measurement accuracy.

[0070] Furthermore, in this embodiment, a group of patterns 63 is a row of adjacent patterns.

[0071] This allows for rapid measurement of the pattern position for calculating the distortion amount D, thereby effectively reducing the measurement time for the distortion amount D.

[0072] Furthermore, in this embodiment, with multiple patterns 62 formed on the substrate 400 to be measured arranged within the measurement field of view 60, the positions of the multiple patterns 62 are measured simultaneously, and the amount of deviation A of the measured positions of the multiple patterns 62 from the multiple design positions is calculated. In addition, the difference E (i.e., second difference) between the amount of deviation A of the measured positions of the multiple patterns 62 and the amount of distortion D is calculated.

[0073] This allows for proper evaluation of drawing conditions by using the measurement results of the pattern position with the distortion amount D corrected.

[0074] (modified version) Furthermore, various modifications shown below can be applied to this embodiment.

[0075] Figure 10 shows a pattern position measurement method according to a first modification of this embodiment. For example, as shown in Figure 10, the row of pattern groups 63 used in the sequential row measurement and simultaneous row measurement described above may have a pitch change between patterns 62 along the y-direction. Even in the case of Figure 10, if the multiple patterns 62 within the field of view 60 have the same pitch change along the y-direction as the row of pattern groups 63, the distortion amount D can be appropriately calculated using the row of pattern groups 63.

[0076] Figure 11 shows a pattern position measurement method according to a second modification of this embodiment. As shown in Figure 11, the size of the pattern 62 in a row of patterns 63 may change along the y-direction. Even in the case of Figure 11, if the multiple patterns 62 within the field of view 60 have the same size change along the y-direction as the row of patterns 63, the distortion amount D can be appropriately calculated using the row of patterns 63.

[0077] Figure 12 shows a pattern position measurement method according to a third modification of this embodiment. As shown in Figure 12, each pattern 62 in a row of pattern group 63 may be circular in shape. Even in the case of Figure 12, by defining the representative position of pattern 62 (for example, the center point) as the position of pattern 62, the amount of distortion D can be appropriately calculated using the row of pattern group 63.

[0078] Figure 13 is a flowchart illustrating a pattern position measurement method according to a fourth modification of this embodiment. Figure 14 is a diagram illustrating a pattern position measurement method according to a fourth modification of this embodiment. Figures 2, 4, and 5 describe an example in which a group of adjacent patterns used to measure the pattern position for calculating the distortion amount D is a row of pattern groups 63.

[0079] In contrast, in the examples shown in Figures 13 and 14, a group of patterns consists of four adjacent rectangular (i.e., block-shaped) pattern groups 63 in both the x and y directions. Accordingly, in the examples shown in Figures 13 and 14, instead of sequential measurement in a row as in Figure 2, sequential measurement of a group at one point within the FOV is performed (step S30). Sequential measurement of a group at one point within the FOV means sequentially measuring the position of each pattern 62 at a reference position P within the field of view 60, while shifting the four adjacent pattern groups 63 (steps S301-304 in Figure 14). Also, in the examples shown in Figures 13 and 14, instead of simultaneous measurement in a row as in Figure 2, simultaneous measurement of a group at multiple points within the FOV is performed (step S50). Simultaneous measurement of a group at multiple points within the FOV means placing the four pattern groups 63 at one of the four sets of four design position groups, which are part of multiple design positions within the field of view 60 and correspond to the four pattern groups 63, and then sequentially shifting the four pattern groups 63 to the other sets of four design position groups, while repeatedly performing simultaneous measurement of the position of each pattern 62 of the four pattern groups 63 (steps S501-503 in Figure 14). Note that sequential measurement of a group and simultaneous measurement of a group are not limited to being applied to four pattern groups 63, but may also be applied to pattern groups 63 of various grouped forms (shape of the entire pattern group, number of patterns, pitch, size, etc.).

[0080] As shown in the examples in Figures 13 and 14, the amount of distortion D can be quickly calculated by sequential measurement of a group and simultaneous measurement of a group. Furthermore, the degree of freedom in selecting a group of patterns 63 used to measure the pattern positions for calculating the amount of distortion D can be improved.

[0081] Figure 15 shows a pattern position measurement method according to a fifth modification of this embodiment. Figures 4 and 5 describe examples of sequential measurement and simultaneous measurement of a row using a row of pattern groups 63 along the y direction. In contrast, the example shown in Figure 15 uses a row of pattern groups 63 along the x direction to perform sequential measurement (steps S31-34) and simultaneous measurement (steps S51-54) of a row. The sequential measurement and simultaneous measurement of a row shown in Figure 15 are basically the same as those in Figures 4 and 5, except that the direction of movement of the XY stage 302 is orthogonal.

[0082] The embodiments described above are presented as examples and are not intended to limit the scope of the invention. The embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, the embodiments described above use a device that performs measurements by light irradiation, but a charged particle beam such as an electron beam may also be used. In that case, the measurement can be performed by scanning the measurement field with the electron beam or the like. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0083] 60 field of view 62 patterns 63 A set of patterns in a row

Claims

1. The process involves shifting a group of divided patterns formed on a substrate to be measured at a reference position within the measurement field of view, sequentially measuring the position of each pattern at the reference position, and calculating the amount of deviation of the measurement position of each pattern from the reference position. A step of placing the group of patterns at one of the multiple design positions which are part of the multiple design positions within the measurement field and correspond to the group of patterns, and then sequentially shifting the group of patterns to the other design positions of the group, while repeatedly and simultaneously measuring the position of each pattern in the group, and calculating the amount of deviation of the measurement position of each pattern from the multiple design positions, A step of calculating a first difference between the amount of deviation of the measurement position of each pattern from the reference position and the amount of deviation of the measurement position of each pattern from the plurality of design positions, A pattern position measurement method comprising the following:

2. The pattern position measurement method according to claim 1, wherein the group of patterns is a row of adjacent patterns.

3. The process involves simultaneously measuring the positions of multiple patterns formed on the substrate to be measured, with the multiple patterns arranged within the measurement field of view, and calculating the amount of deviation of the measurement positions of the multiple patterns from the multiple design positions. A step of calculating a second difference, which is the difference between the amount of deviation of the measurement positions of the multiple patterns and the first difference, The pattern position measurement method according to claim 1, further comprising the following:

4. The aforementioned multiple patterns are formed on the substrate to be measured by etching using a resist pattern drawn with a charged particle beam as a mask. The pattern position measurement method according to claim 3, wherein the drawing conditions for forming the plurality of patterns are each different.

5. The pattern position measurement method according to claim 4, wherein the drawing condition is the focus or dose amount of the charged particle beam.

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