Method and system for calibrating and verifying imaging parameters of scanning electron microscope and electronic equipment

Abstract

The invention discloses a scanning electron microscope imaging parameter calibration verification method and system and electronic equipment, and relates to the technical field of scanning electron microscopes. The method comprises the following steps: arranging a grating sample at a preset initial position; controlling the scanning electron microscope to image the grating sample to obtain a first grating image; moving the grating sample to the imaging view center of the scanning electron microscope according to the first grating image, and imaging the grating sample to obtain a second grating image; calibrating imaging parameters of the scanning electron microscope according to the second grating image; controlling the scanning electron microscope to image the grating sample according to the calibrated imaging parameters to obtain a third grating image; and verifying the imaging parameters of the scanning electron microscope according to the third raster image, and storing the imaging parameters passing the verification.

Description

Technical Field

[0001] The present invention relates to the technical field of scanning electron microscopes, and in particular to a scanning electron microscope imaging parameter calibration verification method, system and electronic equipment. Background Art

[0002] During the operation of a scanning electron microscope, electrical rotation calibration and verification is a critical step, which is of great significance for ensuring image quality and measurement accuracy. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the first object of the present invention is to provide a scanning electron microscope imaging parameter calibration and verification method to achieve accurate calibration and verification of the scanning electron microscope.

[0004] A second objective of the present invention is to provide an electronic device.

[0005] The third object of the present invention is to provide a scanning electron microscope imaging parameter calibration and verification system.

[0006] To achieve the above-mentioned purpose, a first embodiment of the present invention proposes a method for calibrating and verifying imaging parameters of a scanning electron microscope, the method comprising: setting a grating sample at a preset initial position; controlling a scanning electron microscope to image the grating sample to obtain a first grating image; moving the grating sample to the center of the imaging field of view of the scanning electron microscope according to the first grating image, and imaging the grating sample to obtain a second grating image; calibrating the imaging parameters of the scanning electron microscope according to the second grating image; controlling the scanning electron microscope to image the grating sample according to the calibrated imaging parameters to obtain a third grating image; verifying the imaging parameters of the scanning electron microscope according to the third grating image, and saving the verified imaging parameters.

[0007] In addition, the SEM imaging parameter calibration verification method according to the embodiment of the present invention also has the following additional technical features:

[0008] In one embodiment of the present invention, the grating sample is a sample including a plurality of gratings, and the step of moving the grating sample to the center of the imaging field of view of the scanning electron microscope according to the first grating image comprises: determining a target grating from the plurality of gratings according to the first grating image; and moving the grating sample until the grating center of the target grating moves to the center of the imaging field of view.

[0009] In one embodiment of the present invention, determining a target grating from a plurality of gratings according to the first grating image includes: binarizing the first grating image to obtain a binary grating image; identifying gratings in the binary grating image; if the number of gratings in the binary grating image is not within a preset range, adjusting the magnification of the scanning electron microscope, and returning to the step of controlling the scanning electron microscope to image the grating sample to obtain a first grating image, until the number of gratings in the binary grating image is within the preset range; and determining the target grating according to the binary grating image.

[0010] In one embodiment of the present invention, the binarization processing of the first grating image to obtain the binarized grating image includes: converting the first grating image into a grayscale image and obtaining the grayscale value of each pixel in the grayscale image; constructing a grayscale histogram according to the grayscale value and obtaining a grayscale threshold according to the grayscale histogram; binarizing the grayscale image according to the grayscale threshold to obtain the binarized grating image.

[0011] In one embodiment of the present invention, the identifying and obtaining the grating in the binary grating image includes: performing a morphological opening operation on the binary grating image to obtain a denoised binary image; performing a pixel value inversion operation on the denoised binary image to obtain a first inverted binary image; for each pixel in the first inverted binary image, obtaining the closest distance between the pixel and a pixel with a pixel value of 0 in the first inverted binary image, and setting the pixel value of the pixel with the closest distance less than a preset distance threshold to 0 to obtain a second inverted binary image; and identifying the grating in the binary grating image according to the second inverted binary image.

[0012] In one embodiment of the present invention, determining the target grating according to the binary grating image includes: determining the grating closest to the center of the imaging field of view in the binary grating image as the target grating.

[0013] In one embodiment of the present invention, the moving of the grating sample until the grating center of the target grating moves to the center of the imaging field of view includes: moving the grating sample in a first preset direction by a first preset distance, and controlling the scanning electron microscope to image the grating sample to obtain a fourth grating image; obtaining a pixel movement distance of the grating sample on the image according to the fourth grating image and the first grating image; and moving the grating center to the center of the imaging field of view according to the pixel movement distance, the first preset distance and the actual pixel distance, wherein the actual pixel distance is the pixel distance between the grating center and the center of the imaging field of view in the fourth grating image.

[0014] In one embodiment of the present invention, calibrating the imaging parameters of the scanning electron microscope according to the second grating image includes: moving the grating sample in a second preset direction by a second preset distance, controlling the scanning electron microscope to image the grating sample, and obtaining a fifth grating image, wherein the second preset distance is less than half of the first grating size of the grating in the second grating image; moving the grating sample in the second preset direction by a third preset distance, controlling the scanning electron microscope to image the grating sample, and obtaining a sixth grating image; obtaining the electrical rotation angle of the scanning electron microscope according to the second grating image, the fifth grating image, the sixth grating image and the first grating size; and calibrating the imaging parameters of the scanning electron microscope according to the electrical rotation angle.

[0015] In one embodiment of the present invention, the calibrating the imaging parameters of the scanning electron microscope according to the electrical rotation angle includes: determining the maximum magnification according to the second grating image, and adjusting the magnification of the scanning electron microscope to the maximum magnification; controlling the scanning electron microscope to image the grating sample to obtain a seventh grating image; obtaining a second grating size of the grating according to the seventh grating image; obtaining the focusing current of the scanning electron microscope, and calibrating the imaging parameters of the scanning electron microscope according to the second grating size, the focusing current and the electrical rotation angle.

[0016] In one embodiment of the present invention, the obtaining of the electrical rotation angle of the scanning electron microscope according to the second grating image, the fifth grating image, the sixth grating image and the first grating size includes: obtaining a first pixel point set in the second grating image, a second pixel point set in the fifth grating image and a third pixel point set in the sixth grating image of a preset area on the grating sample; obtaining a first pixel distance set between the first pixel point set and corresponding pixels in the second pixel point set, and obtaining a second pixel distance set between the first pixel point set and corresponding pixels in the third pixel point set; determining a target pixel distance in the first pixel distance set according to the first grating size, and obtaining a reference angle according to the target pixel distance; selecting at least one pixel distance from the second pixel distance set according to the first grating size to obtain a selected angle corresponding to the pixel distance; and determining the electrical rotation angle according to the reference angle and the selected angle.

[0017] To achieve the above-mentioned purpose, the second aspect of the present invention proposes an electronic device, including a memory, a processor and a computer program stored in the memory and running on the processor. When the computer program is executed by the processor, the above-mentioned scanning electron microscope imaging parameter calibration and verification method is implemented.

[0018] To achieve the above-mentioned purpose, a third aspect of the present invention provides a scanning electron microscope imaging parameter calibration and verification system, including the above-mentioned electronic device.

[0019] According to the scanning electron microscope imaging parameter calibration and verification method, system and electronic device of the embodiment of the present invention, a grating sample is set at a preset initial position; the scanning electron microscope is controlled to image the grating sample to obtain a first grating image; the grating sample is moved to the center of the imaging field of view of the scanning electron microscope according to the first grating image, and the grating sample is imaged to obtain a second grating image; the imaging parameters of the scanning electron microscope are calibrated according to the second grating image; the scanning electron microscope is controlled to image the grating sample according to the calibrated imaging parameters to obtain a third grating image; the imaging parameters of the scanning electron microscope are verified according to the third grating image, and the verified imaging parameters are saved. In this way, the imaging parameters of the scanning electron microscope can be calibrated and verified. Moreover, before calibration and verification, the grating sample is first moved to the center of the imaging field of view of the scanning electron microscope to ensure the accuracy of subsequent calibration and verification operations.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flow chart of a scanning electron microscope imaging parameter calibration verification method according to an embodiment of the present invention;

[0022] Figure 2 is a binarized raster image of an example of the present invention;

[0023] Figure 3 is a first inverted binary image of an example of the present invention;

[0024] Figure 4 is a second inverted binary image of an example of the present invention;

[0025] Figure 5 It is a result schematic diagram of a scanning electron microscope imaging parameter calibration verification method according to an example of the present invention;

[0026] Figure 6 It is a flow chart of a scanning electron microscope imaging parameter calibration verification method according to an example of the present invention;

[0027] Figure 7 is a structural block diagram of an electronic device according to an embodiment of the present invention;

[0028] Figure 8 It is a structural block diagram of a scanning electron microscope imaging parameter calibration and verification system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following describes a scanning electron microscope imaging parameter calibration verification method, system and electronic device according to an embodiment of the present invention with reference to the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described with reference to the accompanying drawings are exemplary and should not be construed as limiting the present invention.

[0030] Figure 1 The invention discloses a scanning electron microscope imaging parameter calibration verification method according to an embodiment of the present invention.

[0031] like Figure 1 As shown, the scanning electron microscope imaging parameter calibration verification method includes:

[0032] S11, setting the grating sample at a preset initial position.

[0033] Specifically, in order to calibrate and verify the imaging parameters of the scanning electron microscope, a grating sample is set, and the scanning electron microscope is set to scan and image the grating sample, so as to calibrate and verify the imaging parameters according to the imaging results.

[0034] In order to realize scanning and imaging of the grating sample by the scanning electron microscope, it is necessary to first obtain a preset initial position before imaging the grating sample.

[0035] The preset initial position is the initial grating sample position, which may be a fixed position or a position generated based on the historical position during the last calibration verification.

[0036] After obtaining the above preset initial position, it is also necessary to obtain the working conditions for calibration and verification, which include the high voltage for calibration or verification, the beam position for calibration or verification, the working distance for calibration or verification, the magnification of the first calibration or verification under the high voltage, and the height of the grating sample. The above working distance refers to the distance from the grating sample to the objective lens.

[0037] S12, controlling the scanning electron microscope to image the grating sample to obtain a first grating image.

[0038] S13, moving the grating sample to the center of the imaging field of the scanning electron microscope according to the first grating image, and imaging the grating sample to obtain a second grating image.

[0039] Specifically, after obtaining the first grating image, the position of the grating sample in the field of view of the scanning electron microscope can be obtained through the first grating image, and then the grating sample can be moved to the center of the imaging field of view of the scanning electron microscope, thereby ensuring the accuracy of subsequent calibration and verification operations.

[0040] After the grating sample is moved to the center of the imaging field of the scanning electron microscope, the scanning electron microscope can be controlled to image the grating sample again to obtain a second grating image.

[0041] S14, calibrating the imaging parameters of the scanning electron microscope according to the second grating image.

[0042] Specifically, after the second grating image is obtained, the imaging parameters of the scanning electron microscope can be calibrated based on the image to obtain calibrated imaging parameters.

[0043] S15, controlling the scanning electron microscope to image the grating sample according to the calibrated imaging parameters to obtain a third grating image.

[0044] Specifically, after the imaging parameters of the scanning electron microscope are calibrated, the scanning electron microscope can be controlled to image the grating sample again according to the calibrated imaging parameters to obtain a third grating image.

[0045] S16, verifying the imaging parameters of the scanning electron microscope according to the third grating image, and saving the verified imaging parameters.

[0046] Specifically, after the third grating image is obtained, the current imaging parameters of the scanning electron microscope can be verified based on the third grating image. If the current imaging parameters of the scanning electron microscope pass the verification, the verified parameters are saved.

[0047] Thus, the scanning electron microscope can be calibrated and verified. Moreover, before calibration and verification, the grating sample is first moved to the center of the imaging field of view of the scanning electron microscope to ensure the accuracy of subsequent calibration and verification operations.

[0048] In some embodiments of the present invention, for the above working conditions, the working conditions during calibration and the working conditions during verification may be set to be unequal. For example, the user may set the working conditions during calibration and verification as shown in Table 1 below.

[0049] Table 1

[0050] V(KV) CURRENT WD Mag State 30 1 45,35,20,12,11,10,9,8,7,6,5 120 0 30 1 45,35,20,12,11,10,9,8,7,6,5 180 1 30 5 45,35,20,12,11,10,9,8,7,6,5 120 0 30 5 45,35,20,12,11,10,9,8,7,6,5 180 1 20 5 45,35,20,12,11,10,9,8,7,6,5，4,3,2 120 0 20 5 45,35,20,12,11,10,9,8,7,6,5，4,3,2 180 1 20 1 45,35,20,12,11,10,9,8,7,6,5，4,3,2 120 0 20 1 45,35,20,12,11,10,9,8,7,6,5，4,3,2 180 1

[0051] Among them, the above V is the high voltage value, the unit is KV, CURRENT is the beam gear, WD is the above working distance, the unit is millimeter, State is 1 means that the data in the corresponding row is the working condition during verification, and State is 0 means that the data in the corresponding row is the working condition during calibration. Mag is the magnification of the scanning electron microscope. The magnification Mag during the first calibration or verification is set by the user, that is, the Mag in Table 1 above is the magnification of the first calibration or verification.

[0052] In some embodiments of the present invention, the grating sample is a sample including a plurality of gratings.

[0053] It should be noted that, since the grating sample includes multiple gratings, for example, the grating sample includes multiple gratings, and the multiple gratings are divided into 2um, 20um, 200um and 2000um, therefore, when setting the first magnification, the magnification at this time can be set to include a 200um grating within the field of view of the scanning electron microscope, and not more than gratings exceeding 2000um and the above-mentioned entire grating sample.

[0054] At this time, the above-mentioned moving the grating sample to the center of the imaging field of view of the scanning electron microscope according to the first grating image includes: determining the target grating from multiple gratings according to the first grating image; and moving the grating sample until the grating center of the target grating moves to the center of the imaging field of view.

[0055] In some embodiments of the present invention, a target grating is determined from a plurality of gratings according to a first grating image, including: binarizing the first grating image to obtain a binary grating image; identifying gratings in the binary grating image; if the number of gratings in the binary grating image is not within a preset range, adjusting the magnification of a scanning electron microscope, and returning to the step of controlling the scanning electron microscope to image the grating sample to obtain the first grating image, until the number of gratings in the binary grating image is within a preset range; and determining the target grating according to the binary grating image.

[0056] Specifically, in order to determine the target grating from multiple gratings of the grating sample so as to move the center of the target grating to the center of the imaging field of the scanning electron microscope, it is set to first binarize the first grating image to obtain a binary grating image so as to identify the grating in the binary grating image.

[0057] Moreover, after the gratings in the binary grating image are identified, the number of the identified gratings can be counted to obtain the number of gratings in the binary grating image, so as to adjust the magnification of the scanning electron microscope according to the number of gratings.

[0058] For example, when the number of gratings is less than 8, the image is iteratively enlarged, and when the number of gratings is greater than 16, the image is iteratively reduced. If the number of gratings is between 8 and 16, the magnification is appropriate.

[0059] At this time, if the number of gratings is less than 8, the magnification is reduced and the image is enlarged so that the number of gratings in the binary grating image is between 8 and 16.

[0060] If the number of rasters is greater than 16, increase the magnification and reduce the image so that the number of rasters in the binary raster image is between 8 and 16.

[0061] If the number of gratings is between 8 and 16, it means that the magnification is appropriate.

[0062] For example, the magnification factor can be adaptively adjusted according to the number of elements in the detected grating center point coordinate set. When the number of elements is less than 8, the image is iteratively enlarged. If the number is greater than 16, the image is iteratively reduced. If the number is between 8 and 16, the magnification factor is appropriate.

[0063] After adjusting the magnification to a suitable magnification, the target grating can be determined, thereby moving the grating sample to the center of the imaging field of view.

[0064] In some embodiments of the present invention, a first grating image is binarized to obtain a binary grating image, including: converting the first grating image into a grayscale image, and obtaining the grayscale value of each pixel in the grayscale image; constructing a grayscale histogram according to the grayscale value, and obtaining a grayscale threshold according to the grayscale histogram; binarizing the grayscale image according to the grayscale threshold to obtain a binary grating image.

[0065] Specifically, since the pixel value range of the grayscale image is 0-255, the first raster image is first converted into a grayscale image, Gaussian noise reduction is performed, and the grayscale histogram is expanded to 256 elements, and all elements are initialized to 0, and each pixel of the grayscale image is traversed. For each pixel, its grayscale value is used as an index, and the corresponding element in the grayscale histogram is added by 1. In this way, after traversing all pixels, the value of each element in the grayscale histogram represents the number of times the corresponding grayscale value appears in the image. In other words, for the grayscale histogram, its horizontal coordinate is 0-255, a total of 256 pixel values, and the vertical coordinate is the number of times the pixel value corresponding to the horizontal coordinate appears in the grayscale image. In this way, the construction of a grayscale histogram can be achieved.

[0066] Furthermore, the minimum grayscale value and the maximum grayscale value in the grayscale image are obtained according to the grayscale histogram. If the difference between the minimum grayscale value and the maximum grayscale value is less than a preset grayscale difference threshold, the average of the minimum grayscale value and the maximum grayscale value is used as the grayscale threshold.

[0067] If the difference between the minimum grayscale value and the maximum grayscale value is greater than or equal to the preset grayscale difference threshold, the grayscale threshold is obtained according to the following method:

[0068] First, the threshold Threshold=(MaxValue+MinValue) / 2 is calculated, wherein MinValue is the minimum grayscale value and MaxValue is the maximum grayscale value.

[0069] Furthermore, the grayscale histogram from the minimum value to the threshold Threshold is traversed, and the grayscale value average MeanValueOne of all pixels corresponding to this part is calculated. Then the grayscale histogram from the threshold Threshold to the maximum value is traversed, and the grayscale value average MeanValueTwo of all pixels corresponding to this part is calculated. Threshold is updated to (MeanValueOne+MeanValueTwo) / 2. Iteration is stopped until Threshold no longer changes or the number of iterations is greater than the preset number (such as 1000 times), the optimal threshold Threshold is obtained, and the final Threshold is used as the grayscale threshold.

[0070] After obtaining the grayscale threshold, the image can be subjected to adaptive threshold binarization processing using the grayscale threshold to obtain a binary grating image.

[0071] In some embodiments of the present invention, identifying a grating in a binary grating image includes: performing a morphological opening operation on the binary grating image to obtain a denoised binary image; performing a pixel value inversion operation on the denoised binary image to obtain a first inverted binary image; for each pixel in the first inverted binary image, obtaining the closest distance between the pixel and a pixel with a pixel value of 0 in the first inverted binary image, and setting the pixel value of the pixel whose closest distance is less than a preset distance threshold to 0 to obtain a second inverted binary image; and identifying the grating in the binary grating image according to the second inverted binary image.

[0072] Specifically, a morphological opening operation is first performed on the binary raster image, that is, an operation of first erosion and then dilation, to remove noise and smooth the image, thereby obtaining a denoised binary image.

[0073] After obtaining the denoised binary image, it is necessary to perform a pixel value inversion operation on the denoised binary image to obtain a first inverted binary image. Specifically, the pixel value of each pixel in the denoised binary image can be set to be subtracted from 255. At this time, the pixel value of a pixel with a pixel value of 0 becomes 255 after being subtracted from 255, and the pixel value of a pixel with a pixel value of 255 becomes 0 after being subtracted from 255.

[0074] After obtaining the first inverted binary image, the closest distance between each pixel in the first inverted binary image and the pixel with a pixel value of 0 in the first inverted binary image can be obtained, and the pixel value of the pixel whose closest distance is less than the preset distance threshold is set to 0, thereby obtaining the second inverted binary image. For example, the distance between each pixel and the nearest pixel with a pixel value of 0 can be calculated, and the maximum distance disMax can be found, and the preset distance threshold TD=disMax×0.35 can be set, and all pixels whose distance is less than the threshold TD can be set to 0.

[0075] Furthermore, after obtaining the second inverted binary image, the pixel values ​​of the second inverted binary image may be normalized and mapped to a range of 0 to 255, and a grating may be obtained according to the normalized image recognition.

[0076] The following is an explanation with reference to a specific example.

[0077] In this example, the above binarized raster image can be seen in Figure 2 It can be seen that in this example, the grating in the grating sample is a rectangular grating. Figure 2 In the figure, the white part is the grating area and the black part is the non-grating area. Figure 2 The image shown in the figure is inverted to obtain Figure 3 The image shown in Figure 3 In the figure, the portion inside the box pointed by arrow 1 is an example of a grating, and the portion inside the box pointed by arrow 2 is an example of a non-grating area.

[0078] exist Figure 3 In the first inverted binary image shown in FIG. 1 , the black part is the grating and the white part is the non-grating area. At this time, for each pixel in the first inverted binary image, the closest distance between the pixel and the black pixel in the first inverted binary image is obtained, and the pixels whose closest distance is less than the preset distance threshold are converted into black pixels, and the following is obtained: Figure 4 The second inverted binarized image is shown.

[0079] It can be seen that the method of obtaining the second inverted binary image according to the first inverted binary image can remove the black imaging inside the grating in the binary grating image, thereby preventing the black imaging inside the grating in the binary grating image from affecting the grating recognition.

[0080] Specifically, when the scanning electron microscope is imaging the grating sample, not only the pixel values ​​corresponding to the part with grating and the part without grating in the grating sample are different in the first grating image, but also the pixel values ​​corresponding to two different gratings in the first grating image may be different. Therefore, in order to avoid the influence of the different pixel values ​​corresponding to two different gratings in the first grating image on the grating recognition, the first grating image is set to be binarized. Figure 2 As shown in the example, even for a grating, different parts inside it may have different corresponding pixel values ​​in the binary grating image. Therefore, the above method of obtaining the second inverted binary image is adopted to remove the black imaging inside the grating in the binary grating image, so as to avoid the black imaging inside the grating in the binary grating image affecting the grating recognition. Thus, accurate grating recognition can be achieved.

[0081] Next, continue to combine Figure 2 The example shown is used for illustration.

[0082] Specifically, when obtaining Figure 4 After the second inverted binary image is shown, the image contour corresponding to the white part in the second inverted binary image in the binary raster image is found, the edge contour is removed, and the contour is approximated as a quadrilateral convex hull. The obtained contour can be seen in Figure 5 The example indicated by the arrow in the middle. Find the set of all contour center points, and find the vertex coordinates based on the longest distance between the center point and the contour edge to determine the direction of the rectangle.

[0083] Further, three contours are selected from the contours found, and the three contours meet the following conditions: connecting the center points of the three contours can form an isosceles triangle. Find all isosceles triangles that can be obtained by this method, accumulate and average the sizes of the isosceles triangles, and obtain the average pixel size of the grating based on the calculated average value, and connect the vertices of multiple isosceles triangles to obtain the pixel coordinates of the center point of the grating based on the intersection of the connecting lines.

[0084] In some embodiments of the present invention, determining the target grating according to the binary grating image includes: determining the grating closest to the center of the imaging field of view in the binary grating image as the target grating.

[0085] In some embodiments of the present invention, the grating sample is moved until the grating center of the target grating moves to the center of the imaging field of view, including: moving the grating sample in a first preset direction by a first preset distance, and controlling a scanning electron microscope to image the grating sample to obtain a fourth grating image; obtaining a pixel movement distance of the grating sample on the image according to the fourth grating image and the first grating image; and moving the grating center to the center of the imaging field of view according to the pixel movement distance, the first preset distance and the actual pixel distance, wherein the actual pixel distance is the pixel distance between the grating center and the center of the imaging field of view in the fourth grating image.

[0086] The following is an explanation with an example.

[0087] Specifically, since the horizontal and vertical directions of the grating are not necessarily consistent with the X and Y directions when the scanning electron microscope translation stage is shifted, in order to accurately move the grating center of the target grating to the center of the imaging field of view, the center point set vec_center of the grating before the grating sample is moved in the first preset direction by the first preset distance can be first obtained.

[0088] Furthermore, by moving the translation stage in the X direction (i.e., the first preset direction) by a distance x m (i.e., the first preset distance mentioned above), obtain the current grating center point set xvec_center, and calculate the horizontal moving pixel distance of the image as x according to the point coordinates of vec_center and xvec_center d , the vertical distance of moving pixels is y d , let the conversion ratio from unit pixel to actual distance be F d , when the stage moves a unit distance along the X direction, the actual distance c1 moved in the horizontal direction and the actual distance d1 moved in the vertical direction are:

[0089] c1=F d *x d / x m ,

[0090] d1=F d *y d / x m ,

[0091] Similarly, when the grating moves a unit distance along the Y direction, it moves an actual distance c2 in the horizontal direction and an actual distance d2 in the vertical direction.

[0092] Assuming that the original coordinates of a pixel point before moving are A (c, d), and the coordinates after moving (i.e., the center of the imaging field of the scanning electron microscope) are B (e, f), the values ​​of the increase x' and y' in the X-axis and Y-axis directions can be calculated using matrix calculation:

[0093] c+c1*x′+c2*y′=e,

[0094] d+d1*x′+d2*y′=f,

[0095] Convert the above formula into a matrix:

[0096]

[0097] To find this matrix, let the coefficient matrix be:

[0098]

[0099] Right now:

[0100]

[0101] Its inverse matrix is:

[0102]

[0103] Solve according to the determinant:

[0104] det(A)=c1*d2-c2*d1,

[0105] Substituting into:

[0106]

[0107] In some embodiments of the present invention, the imaging parameters of the scanning electron microscope are calibrated according to the second grating image, including: moving the grating sample in a second preset direction by a second preset distance, controlling the scanning electron microscope to image the grating sample, and obtaining a fifth grating image, wherein the second preset distance is less than half of the first grating size of the grating in the second grating image; moving the grating sample in the second preset direction by a third preset distance, controlling the scanning electron microscope to image the grating sample, and obtaining a sixth grating image; obtaining the electrical rotation angle of the scanning electron microscope according to the second grating image, the fifth grating image, the sixth grating image and the first grating size; and calibrating the imaging parameters of the scanning electron microscope according to the electrical rotation angle.

[0108] The above-mentioned calibration of the imaging parameters of the scanning electron microscope according to the electrical rotation angle includes: determining the maximum magnification according to the second grating image, and adjusting the magnification of the scanning electron microscope to the maximum magnification; controlling the scanning electron microscope to image the grating sample to obtain the seventh grating image; obtaining the second grating size of the grating according to the seventh grating image; obtaining the focusing current of the scanning electron microscope, and calibrating the imaging parameters of the scanning electron microscope according to the second grating size, the focusing current and the electrical rotation angle. The above-mentioned confirmation of the maximum magnification according to the second grating image can be the maximum magnification under the premise of satisfying the detection according to the second grating image. Therefore, by obtaining the second grating size, the influence of image distortion on the accuracy can be reduced and the detection accuracy can be improved.

[0109] The method of obtaining the electrical rotation angle of the scanning electron microscope according to the second grating image, the fifth grating image, the sixth grating image and the first grating size includes: obtaining a first pixel point set in the second grating image, a second pixel point set in the fifth grating image and a third pixel point set in the sixth grating image of a preset area on the grating sample; obtaining a first pixel distance set between the first pixel point set and corresponding pixels in the second pixel point set, and obtaining a second pixel distance set between the first pixel point set and corresponding pixels in the third pixel point set; determining a target pixel distance in the first pixel distance set according to the first grating size, and obtaining a reference angle according to the target pixel distance; selecting at least one pixel distance from the second pixel distance set according to the first grating size, and obtaining a selected angle corresponding to the pixel distance; and determining the electrical rotation angle according to the reference angle and the selected angle.

[0110] The following is a specific example. In this example, the raster style can be found in Figure 2 The preset area is a black rectangular area selected from the binarized image after the second grating image is binarized. The black rectangular area can be seen in Figure 2 The non-grating area in is referred to as the black rectangular area at the current position hereinafter.

[0111] Specifically, the black rectangle area coordinate set vec1_center of the current position is obtained, that is, the first pixel point set is the set of all pixel points corresponding to the selected black rectangle in the second raster image, and the current raster average size S is obtained. t (ie the first grating size mentioned above).

[0112] Move a fixed distance x1 (the second preset distance) in the X direction to obtain the black rectangular area coordinate set vec1_center1 at the current position, that is, the pixel coordinates of each pixel point in the second pixel point set in the image, that is, the second pixel point set is the set of all pixel points corresponding to the selected black rectangle in the fifth raster image.

[0113] After obtaining the second pixel point set, move a fixed distance x2 (the third preset distance) in the X direction to obtain the black rectangular area coordinate set vec1_center2 at the current position, that is, the pixel coordinates of each pixel point in the third pixel point set in the image, that is, the third pixel point set is the set of all pixel points corresponding to the selected black rectangle in the sixth raster image.

[0114] Furthermore, by using the coordinate sets vec1_center and vec1_center1, the distance between the point of vec1_center and the point of vec1_center1 is calculated, and the distance is less than S t The matching point is calculated, and the angle between the two points is obtained to obtain the reference angle angle1.

[0115] It should be noted that, when there are more than one pair of matching points, any one pair can be selected as the matching points for finally obtaining the reference angle.

[0116] After obtaining angle1, use angle1 as the angle limit and size S t As a distance limit, calculate the distance D and angle angle between the point in vec1_center and the point in vec1_center2, where:

[0117] 2S t <D<4S t ,

[0118] |angle-angle1|<5,

[0119] Iteratively search for the minimum value of |angle-angle1| as the final matching result to obtain the electrical rotation angle angle.

[0120] After obtaining the electrical rotation angle angle and the second grating size obtained at the maximum magnification, the imaging parameters of the scanning electron microscope can be calibrated based on the electrical rotation angle, the second grating size and the focusing current.

[0121] In some embodiments of the present invention, since switching high voltage, beam current and moving the Z axis may cause image offset, a parameter transfer method is used to solve this problem.

[0122] above Figure 3 For example, when the working distance is 5 or other working conditions under high pressure, the field of view may be small, resulting in the failure of the grating detection method when the grating center position is moved to the image center, that is, there are no three complete black rectangular areas. Therefore, the movement of the grating center position to the image center in the previous working condition can be recorded in real time, and appropriate compensation can be made for the working condition to make the grating center offset from the center point smaller.

[0123] Under the same high pressure, the amplification factor of the last calibration or verification will be used as a reference for the next calibration or verification.

[0124] Under different high voltage and beam current conditions, the coordinates of moving the grating center position to the image center during the first calibration will be recorded and updated in real time, and will be passed to the first calibration or verification of the next high voltage and beam current to provide a position reference.

[0125] In some embodiments of the present invention, when verifying the imaging parameters according to the third grating image, the adopted method may refer to the method for calibrating the imaging parameters according to the second grating image.

[0126] Combine the following Figure 6 The specific example shown is used for explanation.

[0127] Specifically, this example includes the following steps:

[0128] Move the grating sample to the initial position, lock MR to 1, and lock the rotation angle to 0.

[0129] The initial position is a preset initial position, that is, a preset initial position of the grating sample when the calibration is performed for the first time. The above MR is a magnification correction factor.

[0130] Get the parameters Param required for calibration and verification from the configuration file.

[0131] Switch the high voltage or beam gear according to Param.

[0132] If switching is required, switch the high voltage or beam gear.

[0133] The sample stage moves to the coordinate of point O. If point O does not exist, it does not move.

[0134] Specifically, if this is the first calibration, the sample stage will not be moved because there is no parameter information about the center of the scanning electron microscope imaging field of view. If this is not the first calibration, parameter information about the center of the scanning electron microscope imaging field of view is available, so the sample stage can be moved based on the parameter information.

[0135] That is to say, if the current calibration is the first time, the preset initial position is the initial position; if the current calibration is not the first time, the preset initial position is the position obtained based on the known center of the scanning electron microscope imaging field of view.

[0136] Set the initial magnification according to the Param parameter.

[0137] The Param is the working condition of the scanning electron microscope, which is an externally input and modifiable parameter of the auxiliary algorithm imaging.

[0138] When the initial magnification has been set or does not need to be switched, move the Z axis to the specified WD height.

[0139] Perform automatic degaussing, automatic brightness, automatic focus, automatic astigmatism, etc. to adjust the image to be clear.

[0140] Adaptively adjust the magnification Mag according to the algorithm detection.

[0141] The adaptive adjustment of the magnification factor is to adjust the number of gratings in the binary grating image to within a preset range.

[0142] It should be noted that, in the adaptive adjustment of the magnification, under the same voltage, when calibrating or verifying for different working distances, only one magnification needs to be set, and the magnifications of the remaining working distances can be determined based on the magnification of the previous working distance calibration.

[0143] The center position of the grating is moved to the center of the image according to the algorithm calculation, and the coordinate moved to the center position during the first calibration under high pressure is marked as O.

[0144] The center of the image is the center of the imaging field of the scanning electron microscope.

[0145] The electrical rotation angle of the detection grating is calculated according to the algorithm.

[0146] The magnification is adjusted adaptively, and the average size of the grating is obtained according to the algorithm detection.

[0147] Get the focusing current under this condition.

[0148] The grating size, focusing current and electrical rotation angle under this working condition are counted.

[0149] Determine whether all working conditions under this high voltage have been calibrated or verified. If not, pass the magnification Mag under this working condition, return to the above step of moving the Z axis to the specified WD height, if it has been completed, determine whether the calibration or verification has been completed, if the calibration has been completed, write the parameter set into the software, unlock, return to the above step of moving the sample stage to the coordinate of point O, start verification, if the verification has been completed, return to the above step of judging the switching of high voltage or beam gear according to Param, and start calibrating the next high voltage.

[0150] The grating size under the above working condition is the above second grating size, that is, the average grating size obtained by the above algorithm detection.

[0151] Among them, after obtaining the second grating size, focusing current, and electric rotation angle of all preset calibration distances under high voltage, the scanning electron microscope imaging can be verified based on the calibration parameters, and the grating size, electric rotation angle, and working distance for clear imaging of the scanning electron microscope at different verification distances under the high voltage can be verified. For example, the electric rotation function of the scanning electron microscope can be calibrated or verified based on the electric rotation angle, the grating scanning size of the scanning electron microscope can be calibrated and verified based on the second grating size, and the working distance can be calibrated or verified based on the focusing current.

[0152] The above calibration distance is the working distance during calibration, and the above verification distance is the working distance during verification.

[0153] The reason why the above-mentioned magnification Mag under the working condition is set is that under the same voltage, when calibrating or verifying for different working distances, only one magnification needs to be set, and the magnifications of the remaining working distances will be determined according to the magnification of the previous working distance calibration.

[0154] In summary, the scanning electron microscope imaging parameter calibration and verification method of the embodiment of the present invention sets the grating sample at a preset initial position; controls the scanning electron microscope to image the grating sample to obtain a first grating image; moves the grating sample to the center of the imaging field of view of the scanning electron microscope according to the first grating image, and images the grating sample to obtain a second grating image; calibrates the imaging parameters of the scanning electron microscope according to the second grating image; controls the scanning electron microscope to image the grating sample according to the calibrated imaging parameters to obtain a third grating image; verifies the imaging parameters of the scanning electron microscope according to the third grating image, and saves the verified imaging parameters. In this way, the imaging parameters of the scanning electron microscope can be calibrated and verified. Moreover, before calibration and verification, the grating sample is first moved to the center of the imaging field of the scanning electron microscope to ensure the accuracy of subsequent calibration and verification operations.

[0155] Furthermore, the present invention provides an electronic device.

[0156] Figure 7 It is a structural block diagram of an electronic device according to an embodiment of the present invention.

[0157] like Figure 7 As shown, the electronic device 500 includes: a processor 501 and a memory 503. The processor 501 and the memory 503 are connected, such as through a bus 502. Optionally, the electronic device 500 may also include a transceiver 504. It should be noted that in actual applications, the transceiver 504 is not limited to one, and the structure of the electronic device 500 does not constitute a limitation on the embodiments of the present invention.

[0158] Processor 501 may be a CPU (Central Processing Unit), a general purpose processor, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. It may implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of the present invention. Processor 501 may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc.

[0159] The bus 502 may include a path to transmit information between the above components. The bus 502 may be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus. The bus 502 may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 7 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0160] The memory 503 is used to store a computer program corresponding to the scanning electron microscope imaging parameter calibration verification method of the above embodiment of the present invention, and the computer program is controlled and executed by the processor 501. The processor 501 is used to execute the computer program stored in the memory 503 to implement the content shown in the above method embodiment.

[0161] in, Figure 7 The electronic device 500 shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present invention.

[0162] The electronic device of the embodiment of the present invention can calibrate and verify the scanning electron microscope by implementing the scanning electron microscope imaging parameter calibration and verification method of the above embodiment.

[0163] Furthermore, the present invention proposes a scanning electron microscope imaging parameter calibration and verification system.

[0164] Figure 8 It is a structural block diagram of a scanning electron microscope imaging parameter calibration and verification system according to an embodiment of the present invention.

[0165] like Figure 8 As shown, the SEM imaging parameter calibration and verification system 10 includes the electronic device 500 mentioned above.

[0166] The scanning electron microscope imaging parameter calibration and verification system of the embodiment of the present invention can realize calibration and verification of the scanning electron microscope through the electronic equipment of the above embodiment.

[0167] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0168] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiment, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0169] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0170] In the description of this specification, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as a limitation on the present invention.

[0171] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0172] In the description of this specification, unless otherwise specified, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0173] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0174] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A scanning electron microscope imaging parameter calibration verification method, characterized in that: The method comprises: Setting the grating sample at a preset initial position; Controlling a scanning electron microscope to image the grating sample to obtain a first grating image; According to the first grating image, the grating sample is moved to the center of the imaging field of the scanning electron microscope, and the grating sample is imaged to obtain a second grating image; calibrating imaging parameters of the scanning electron microscope according to the second grating image; Controlling the scanning electron microscope to image the grating sample according to the calibrated imaging parameters to obtain a third grating image; The imaging parameters of the scanning electron microscope are verified according to the third grating image, and the verified imaging parameters are saved.

2. The scanning electron microscope imaging parameter calibration verification method according to claim 1, characterized in that: The grating sample is a sample including a plurality of gratings, and the step of moving the grating sample to the center of the imaging field of view of the scanning electron microscope according to the first grating image comprises: determining a target grating from a plurality of the gratings according to the first grating image; The grating sample is moved until the grating center of the target grating moves to the center of the imaging field of view.

3. The scanning electron microscope imaging parameter calibration verification method according to claim 2, characterized in that: Determining a target grating from a plurality of gratings according to the first grating image comprises: Performing binarization processing on the first grating image to obtain a binarized grating image; Identify a grating in the binary grating image; If the number of gratings in the binary grating image is not within the preset range, adjusting the magnification of the scanning electron microscope, and returning to the step of controlling the scanning electron microscope to image the grating sample to obtain a first grating image, until the number of gratings in the binary grating image is within the preset range; The target raster is determined according to the binary raster image.

4. The scanning electron microscope imaging parameter calibration verification method according to claim 3, characterized in that: The binarization process is performed on the first grating image to obtain a binarized grating image, comprising: Converting the first raster image into a grayscale image, and obtaining the grayscale value of each pixel in the grayscale image; Constructing a grayscale histogram according to the grayscale value, and obtaining a grayscale threshold according to the grayscale histogram; The grayscale image is binarized according to the grayscale threshold to obtain the binarized grating image.

5. The scanning electron microscope imaging parameter calibration verification method according to claim 4, characterized in that: The step of identifying and obtaining a grating in the binary grating image comprises: Performing a morphological opening operation on the binary raster image to obtain a denoised binary image; Performing a pixel value inversion operation on the denoised binary image to obtain a first inverted binary image; For each pixel in the first inverted binary image, the shortest distance between the pixel and a pixel whose pixel value is 0 in the first inverted binary image is obtained, and the pixel value of the pixel whose shortest distance is less than a preset distance threshold is set to 0, so as to obtain a second inverted binary image; A raster in the binarized raster image is identified based on the second inverse binarized image.

6. The scanning electron microscope imaging parameter calibration verification method according to claim 3, characterized in that: The step of determining the target grating according to the binary grating image comprises: The grating closest to the center of the imaging field of view in the binary grating image is determined as the target grating.

7. The scanning electron microscope imaging parameter calibration verification method according to claim 2, characterized in that: The step of moving the grating sample until the grating center of the target grating moves to the center of the imaging field of view comprises: Move the grating sample in a first preset direction by a first preset distance, and control the scanning electron microscope to image the grating sample to obtain a fourth grating image; Obtaining a pixel movement distance of the grating sample on the image according to the fourth grating image and the first grating image; The grating center is moved to the center of the imaging field of view according to the pixel movement distance, the first preset distance and the actual pixel distance, wherein the actual pixel distance is the pixel distance between the grating center and the center of the imaging field of view in the fourth grating image.

8. The scanning electron microscope imaging parameter calibration verification method according to claim 2, characterized in that: The step of calibrating the imaging parameters of the scanning electron microscope according to the second grating image comprises: Move the grating sample in a second preset direction by a second preset distance, control the scanning electron microscope to image the grating sample, and obtain a fifth grating image, wherein the second preset distance is less than half of the first grating size of the grating in the second grating image; Move the grating sample in the second preset direction by a third preset distance, and control the scanning electron microscope to image the grating sample to obtain a sixth grating image; Obtaining the electrical rotation angle of the scanning electron microscope according to the second grating image, the fifth grating image, the sixth grating image and the first grating size; The imaging parameters of the scanning electron microscope are calibrated according to the electrical rotation angle.

9. The scanning electron microscope imaging parameter calibration verification method according to claim 8, characterized in that: The step of calibrating the imaging parameters of the scanning electron microscope according to the electrical rotation angle comprises: determining a maximum magnification according to the second grating image, and adjusting the magnification of the scanning electron microscope to the maximum magnification; Controlling the scanning electron microscope to image the grating sample to obtain a seventh grating image; Obtaining a second grating size of the grating according to the seventh grating image; The focusing current of the scanning electron microscope is obtained, and the imaging parameters of the scanning electron microscope are calibrated according to the second grating size, the focusing current and the electrical rotation angle.

10. The scanning electron microscope imaging parameter calibration verification method according to claim 8, characterized in that: The step of obtaining the electrical rotation angle of the scanning electron microscope according to the second grating image, the fifth grating image, the sixth grating image and the first grating size comprises: Obtaining a first pixel point set of a preset area on the grating sample in the second grating image, a second pixel point set in the fifth grating image, and a third pixel point set in the sixth grating image; Obtaining a first pixel distance set between the first pixel point set and corresponding pixel points in the second pixel point set, and obtaining a second pixel distance set between the first pixel point set and corresponding pixel points in the third pixel point set; Determine a target pixel distance in the first pixel distance set according to the first grating size, and obtain a reference angle according to the target pixel distance; Selecting at least one pixel distance from the second pixel distance set according to the first grating size to obtain a selected angle corresponding to the pixel distance; The electrical rotation angle is determined according to the reference angle and the candidate angle.

11. An electronic device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and running on the processor. When the computer program is executed by the processor, the scanning electron microscope imaging parameter calibration verification method according to any one of claims 1 to 10 is implemented.

12. A scanning electron microscope imaging parameter calibration verification system, characterized in that: Comprising the electronic device according to claim 11.

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