Scanning electron microscope imaging parameter calibration verification method, system and electronic device

Abstract

The application 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: setting 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 center of the imaging field of the scanning electron microscope according to the first grating image, imaging the grating sample, and obtaining 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, and obtaining 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.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of scanning electron microscopy, and in particular to a scanning electron microscope imaging parameter calibration and verification method and system, and an electronic device. BACKGROUND

[0002] In the operation process of a scanning electron microscope, electrical rotation calibration and verification is a key step, which is of great significance to ensure image quality and measurement accuracy. SUMMARY

[0003] The present application aims to at least partially solve one of the technical problems in the related art. To this end, a first object of the present application is to provide a scanning electron microscope imaging parameter calibration and verification method to accurately calibrate and verify a scanning electron microscope.

[0004] A second object of the present application is to provide an electronic device.

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

[0006] To achieve the above-mentioned objects, a scanning electron microscope imaging parameter calibration and verification method according to an embodiment of the present application is provided, which comprises: 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 scanning electron microscope imaging parameter calibration and verification method according to the embodiment of the present application also has the following technical features:

[0008] In an embodiment of the present application, the grating sample is a sample comprising a plurality of gratings, and 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 center of the target grating moves to the center of the imaging field of view.

[0009] In one embodiment of the present application, the determining the target grating from the plurality of gratings according to the first grating image comprises: performing a binarization process on the first grating image to obtain a binarized grating image; identifying the gratings in the binarized grating image; if the number of gratings in the binarized 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 binarized grating image is within the preset range; and determining the target grating according to the binarized grating image.

[0010] In one embodiment of the present application, the binarization process on the first grating image to obtain a binarized grating image comprises: 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 value according to the grayscale histogram; and performing a binarization process on the grayscale image according to the grayscale threshold value to obtain the binarized grating image.

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

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

[0013] In one embodiment of the present application, the moving the grating sample until the grating center of the target grating moves to the center of the imaging field of view comprises: 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 the 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 on the image 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 application, the calibration of the imaging parameters of the scanning electron microscope according to the second grating image comprises: moving the grating sample to a second preset direction by a second preset distance, controlling the scanning electron microscope to image the grating sample to 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; moving the grating sample to the second preset direction by a third preset distance, controlling 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; and calibrating the imaging parameters of the scanning electron microscope according to the electrical rotation angle.

[0015] In one embodiment of the present application, the calibration of the imaging parameters of the scanning electron microscope according to the electrical rotation angle comprises: 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 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.

[0016] In one embodiment of the present application, 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 comprises: obtaining a first set of pixel points of a preset area on the grating sample in the second grating image, a second set of pixel points of the preset area in the fifth grating image and a third set of pixel points of the preset area in the sixth grating image; obtaining a first set of pixel distances of corresponding pixel points in the first set of pixel points and the second set of pixel points, and obtaining a second set of pixel distances of corresponding pixel points in the first set of pixel points and the third set of pixel points; determining a target pixel distance in the first set of pixel distances 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 set of pixel distances according to the first grating size to obtain a candidate angle corresponding to the pixel distance; and determining the electrical rotation angle according to the reference angle and the candidate angle.

[0017] To achieve the above object, a second embodiment of the present application provides an electronic device, comprising a memory, a processor and a computer program stored in the memory and running on the processor, wherein the computer program is executed by the processor to implement the scanning electron microscope imaging parameter calibration verification method.

[0018] To achieve the above object, the third aspect of the present application provides a scanning electron microscope imaging parameter calibration and verification system, comprising the electronic device.

[0019] According to the scanning electron microscope imaging parameter calibration and verification method, system and electronic device, the 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 imaging parameters that pass the verification are saved. Thus, 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, so that the accuracy of subsequent calibration and verification operations can be ensured.

[0020] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a flowchart of the scanning electron microscope imaging parameter calibration and verification method of the embodiment of the present application;

[0022] Figure 2 is a binary grating image of one example of the present application;

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

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

[0025] Figure 5 is a result schematic diagram of the scanning electron microscope imaging parameter calibration and verification method of one example of the present application;

[0026] Figure 6 is a flowchart of the scanning electron microscope imaging parameter calibration and verification method of one example of the present application;

[0027] Figure 7 is a structural block diagram of the electronic device of the embodiment of the present application;

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

[0029] A scanning electron microscope imaging parameter calibration verification method, system and electronic device are described below with reference to the accompanying drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described with reference to the accompanying drawings are exemplary and should not be construed as limiting the present application.

[0030] Figure 1 The scanning electron microscope imaging parameter calibration verification method is an embodiment of the present application.

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

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

[0033] Specifically, in order to realize calibration and verification of the imaging parameters of the scanning electron microscope, the grating sample is set, and the scanning electron microscope is set to scan the grating sample 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, the preset initial position needs to be obtained first before imaging the grating sample.

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

[0036] After obtaining the preset initial position, the working conditions during calibration and verification are also needed, including the high voltage for calibration or verification, the beam current gear for calibration or verification, the working distance for calibration or verification, the magnification for the first calibration or verification under the high voltage, and the grating sample height. The 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 view 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. In this way, the accuracy of subsequent calibration and verification operations can be ensured.

[0040] After the grating sample is moved to the center of the imaging field of view of the scanning electron microscope, the scanning electron microscope is 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 are 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 calibration of the imaging parameters of the scanning electron microscope is completed, the scanning electron microscope is 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 are 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] In this way, the calibration and verification of the scanning electron microscope can be realized. Moreover, before the calibration and verification, the grating sample is first moved to the center of the imaging field of view of the scanning electron microscope, which can ensure the accuracy of subsequent calibration and verification operations.

[0048] In some embodiments of the present application, for the above working conditions, the working conditions when calibration is performed and the working conditions when verification is performed can be set to be not completely equal. For example, the user can set the working conditions when calibration and verification are performed as shown in Table 1.

[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] wherein V is a high voltage value, in KV, CURRENT is a beam current gear, WD is the working distance, in millimeters, and State is 1 if the data in the corresponding row is the working condition when verification is performed, and State is 0 if the data in the corresponding row is the working condition when calibration is performed. Mag is the magnification of the scanning electron microscope, and the magnification Mag when the calibration or verification is performed for the first time is set by the user, i.e., Mag in Table 1 above is the magnification when the calibration or verification is performed for the first time.

[0052] In some embodiments of the present application, 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, when the first magnification is set, the magnification at this time can be set to include a 200um grating in the field of view of the scanning electron microscope, and not more than 2000um gratings and the entire grating sample.

[0054] At this time, the above 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 a target grating from the multiple gratings according to the first grating image; and moving the grating sample until the center of the target grating moves to the center of the imaging field of view.

[0055] In some embodiments of the present application, the target grating is determined from the multiple gratings according to the first grating image, including: performing binaryzation processing on the first grating image to obtain a binaryzation grating image; identifying the gratings in the binaryzation grating image; if the number of gratings in the binaryzation 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 the first grating image until the number of gratings in the binaryzation grating image is within the preset range; and determining the target grating according to the binaryzation grating image.

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

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

[0058] For example, the number of gratings is less than 8, the image is enlarged iteratively, the number of gratings is greater than 16, the image is reduced iteratively, and 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 binaryzation grating image is between 8 and 16.

[0060] If the number of gratings is greater than 16, the magnification is increased and the image is reduced, so that the number of gratings in the binaryzation grating image is between 8 and 16.

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

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

[0063] After the magnification factor is adjusted to an appropriate magnification factor, the target grating can be determined, so that the grating sample can be moved to the center of the imaging field of view.

[0064] In some embodiments of the present application, the first grating image is subjected to binarization processing to obtain a binarized 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 values and obtaining a grayscale threshold value according to the grayscale histogram; and performing binarization processing on the grayscale image according to the grayscale threshold value to obtain the binarized grating image.

[0065] Specifically, since the pixel value range of the grayscale image is 0-255, the first grating image is first converted into a grayscale image, subjected to Gaussian noise reduction processing, and the grayscale histogram is expanded to 256 elements, and all elements are initialized to 0. Each pixel of the grayscale image is traversed. For each pixel, the corresponding element in the grayscale histogram is incremented by 1 using its grayscale value as an index. In this way, when all pixels are traversed, the value of each element in the grayscale histogram represents the number of times the corresponding grayscale value appears in the image. That is, for this grayscale histogram, the horizontal coordinate is 256 pixel values from 0 to 255, and the vertical coordinate is the number of times the pixel value corresponding to the horizontal coordinate appears in the grayscale image. Thus, the grayscale histogram can be constructed.

[0066] Further, the minimum grayscale value and the maximum grayscale value in the above grayscale histogram 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 taken as the grayscale threshold value.

[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 above grayscale threshold value is obtained according to the following method:

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

[0069] Further, the average value MeanValueOne of the gray values of all pixel points corresponding to the part from the minimum value to the threshold value Threshold in the gray scale histogram is calculated, the average value MeanValueTwo of the gray values of all pixel points corresponding to the part from the threshold value Threshold to the maximum value in the gray scale histogram is calculated, the threshold value Threshold is updated as Threshold = (MeanValueOne + MeanValueTwo) / 2, and the iteration is stopped until the threshold value Threshold does not change or the iteration number is greater than a preset number (such as 1000 times), the optimal threshold value Threshold is obtained, and the final threshold value Threshold obtained is taken as the gray threshold value.

[0070] After the gray threshold value is obtained, the image can be adaptively threshold binarized by using the gray threshold value to obtain a binarized raster image.

[0071] In some embodiments of the present application, the raster in the binarized raster image is identified, including: performing a morphological opening operation on the binarized raster image to obtain a denoised binarized image; performing a pixel value inversion operation on the denoised binarized image to obtain a first inverted binarized image; for each pixel in the first inverted binarized image, the nearest distance between the pixel and a pixel with a pixel value of 0 in the first inverted binarized image is obtained, and the pixel value of a pixel with a nearest distance less than a preset distance threshold is set to 0 to obtain a second inverted binarized image; and the raster in the binarized raster image is identified according to the second inverted binarized image.

[0072] Specifically, first, the morphological opening operation is performed on the binarized raster image, that is, the operation of first erosion and then dilation, to smooth the image and obtain the denoised binarized image.

[0073] After the denoised binarized image is obtained, the pixel value inversion operation is further performed on the denoised binarized image to obtain the first inverted binarized image, and specifically, the pixel value of each pixel in the denoised binarized image can be set to 255 minus, at this time, the pixel value of a pixel with a pixel value of 0 is 255 after being subtracted by 255, and the pixel value of a pixel with a pixel value of 255 is 0 after being subtracted by 255.

[0074] After obtaining the first inverted binarization image, the nearest distance between each pixel in the first inverted binarization image and a pixel with a pixel value of 0 in the first inverted binarization image is obtained, and the pixel value of a pixel with a nearest distance less than a preset distance threshold is set to 0 to obtain a second inverted binarization 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 is found, the preset distance threshold TD is set to disMax*0.35, and all pixels with a distance less than the threshold TD are set to 0.

[0075] Further, after obtaining the second inverted binarization image, the pixel values of the second inverted binarization image can be normalized to a range of 0-255, and a grating is identified according to the normalized image.

[0076] The following will be described in combination with a specific example.

[0077] In the example, the above-mentioned binarization grating image can refer to Figure 2 It can be seen that, in the example, the grating in the above-mentioned grating sample is a rectangular grating. Figure 2 In the example, the white part is a grating, and the black part is a non-grating area. Figure 2 The pixel value inversion operation on the image shown in Figure 3 can obtain the image shown in Figure 3 In the example, the part inside the box pointed by the arrow 1 is an example of a grating, and the part inside the box pointed by the arrow 2 is an example of a non-grating area.

[0078] In the first inverted binarization image shown in Figure 3 , the black part is a grating, and the white part is a non-grating area. At this time, for each pixel in the first inverted binarization image, the nearest distance between the pixel and a black pixel in the first inverted binarization image is obtained, and the pixel with a nearest distance less than a preset distance threshold is converted to a black pixel to obtain the second inverted binarization image shown in Figure 4 .

[0079] It can be seen that, by the above-mentioned method of obtaining the second inverted binarization image from the first inverted binarization image, the black imaging inside the grating in the above-mentioned binarization grating image can be removed, and the influence of the black imaging inside the grating in the above-mentioned binarization grating image on grating identification can be avoided.

[0080] Specifically, when the scanning electron microscope images the grating sample, not only the pixel values corresponding to the grating and non-grating parts in the first grating image are different, but also the pixel values corresponding to two different gratings in the first grating image can be different. Therefore, in order to avoid the influence of the pixel values corresponding to the two different gratings in the first grating image on grating identification, the first grating image is subjected to a binarization process. As shown in the example of Figure 2 , even for one grating, the pixel values corresponding to different parts inside the grating in the binarized grating image can be different. Therefore, the above method of obtaining the second inverted binarized image is adopted to remove the black imaging of the grating inside the above binarized grating image and avoid the influence of the black imaging of the grating inside the above binarized grating image on grating identification. Thus, accurate grating identification can be achieved.

[0081] The following will continue to be described in combination with the example shown in Figure 2 .

[0082] Specifically, after obtaining the second inverted binarized image as shown in Figure 4 , the image contour corresponding to the white part in the second inverted binarized image in the binarized grating image is found, the edge contour is removed, and the contour is approximated to a quadrilateral convex hull. The obtained contour can be seen in the example indicated by the arrow in Figure 5 . The set of all contour center points is calculated, and the vertex coordinates are calculated according to 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 found contours, which satisfy the following conditions: the center points of the three contours can form an isosceles triangle. All isosceles triangles obtained in this way are found, the size of the isosceles triangle is accumulated and averaged, and the average pixel size of the grating is obtained based on the calculated average value. The vertices of the multiple isosceles triangles are connected to each other, and the grating center point pixel coordinates can be obtained based on the intersection of the connecting lines.

[0084] In some embodiments of the present application, the target grating is determined according to the binarized grating image, including: determining the grating closest to the center of the imaging field of view in the binarized grating image as the target grating.

[0085] In some embodiments of the present application, moving the grating sample until the grating center of the target grating is moved to the center of the imaging field of view comprises: 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 an actual pixel distance, wherein the actual pixel distance is a pixel distance on the image between the grating center and the center of the imaging field of view in the fourth grating image.

[0086] The following will be described in conjunction with an example.

[0087] Specifically, since the horizontal and vertical directions of the grating are not necessarily consistent with the X and Y methods when the scanning electron microscope displacement table is displaced, 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 obtained first.

[0088] Further, by moving the displacement table in the X direction (i.e. the first preset direction) by a distance x m (i.e. the first preset distance), the current grating center point set xvec_center is obtained, and the horizontal movement pixel distance of the image is calculated as x d and the vertical movement pixel distance is calculated as y d , and the conversion ratio of a unit pixel to an actual distance is F d , then when the displacement table moves by a unit distance in the X direction, the horizontal actual distance c1 and the vertical actual distance d1 are:

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

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

[0091] Similarly, when moving by a unit distance in the Y direction, the horizontal actual distance c2 and the vertical actual distance d2 of the grating are obtained.

[0092] Suppose a pixel point has original coordinates A (c, d) before movement and coordinates B (e, f) after movement (i.e. the center of the imaging field of view of the scanning electron microscope), then the values of the X-axis and Y-axis direction increments x' and y' can be calculated using a matrix:

[0093] c + c1*x' + c2*y' = e,

[0094] d + d1*x' + d2*y' = f,

[0095] Convert the above formula to matrix:

[0096]

[0097] Solve the matrix, set the coefficient matrix:

[0098]

[0099] That is:

[0100]

[0101] Its inverse matrix is:

[0102]

[0103] According to the determinant:

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

[0105] Substitute it into:

[0106]

[0107] In some embodiments of the present application, the imaging parameters of the scanning electron microscope are calibrated according to the second grating image, including: moving the grating sample to a second preset direction by a second preset distance, controlling the scanning electron microscope to image the grating sample to 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; moving the grating sample to the second preset direction by a third preset distance, controlling 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; and calibrating the imaging parameters of the scanning electron microscope according to the electrical rotation angle.

[0108] The imaging parameter calibration 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 a focus current of the scanning electron microscope, and calibrating the imaging parameter of the scanning electron microscope according to the second grating size, the focus current and the electrical rotation angle. The above-mentioned determining the maximum magnification according to the second grating image can determine the maximum magnification that meets the detection premise according to the second grating image. Thus, 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 electrical rotation angle of the scanning electron microscope is obtained according to the second grating image, the fifth grating image, the sixth grating image and the first grating size, including: obtaining a first set of pixel points of a preset region on the grating sample in the second grating image, a second set of pixel points in the fifth grating image and a third set of pixel points in the sixth grating image; obtaining a first set of pixel distances of corresponding pixel points in the first set of pixel points and the second set of pixel points, and obtaining a second set of pixel distances of corresponding pixel points in the first set of pixel points and the third set of pixel points; determining a target pixel distance in the first set of pixel distances 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 set of pixel distances according to the first grating size to obtain a candidate angle corresponding to the pixel distance; and determining the electrical rotation angle according to the reference angle and the candidate angle.

[0110] The following will be described in conjunction with a specific example. In this example, the pattern of the grating can be seen from Figure 2 The preset region is a black rectangular region selected from the binarized image after binarizing the second grating image, which can be seen from the non-grating region in Figure 2 , which is referred to as the black rectangular region of the current position hereinafter.

[0111] Specifically, the set of coordinates of the black rectangular region of the current position vec1_center is obtained, that is, the first set of pixel points is the set of all pixel points corresponding to the selected black rectangular region in the second grating image, and the current grating average size S t (i.e. the first grating size) is obtained.

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

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

[0114] Further, by the coordinate sets vec1_center and vec1_center1, the distance between the point positions of vec1_center and vec1_center1 is calculated, and the point positions that are less than S t are the matching point positions, the angle between the two point positions is calculated to obtain the reference angle angle1.

[0115] It should be noted that when there is more than one matching point position, one pair is selected as the final matching point position used to obtain the reference angle.

[0116] After obtaining angle1, take angle1 as the angle limit, and take S t as the distance limit, calculate the distance D and the angle angle between the point positions in vec1_center and vec1_center2, wherein:

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

[0118] |angle-angle1|<5,

[0119] Iteratively find 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 application, due to the switching of high voltage, beam current and moving Z axis, image offset may occur, and the parameter transfer method is used to solve the problem.

[0122] The above Figure 3 For example, in other working conditions under high voltage with a working distance of 5 or more, the field of view may be small, resulting in that the grating center position is not moved to the image center, that is, there are not three complete black rectangular regions. Thus, the movement of the grating center position to the image center in the last working condition can be recorded in real time, and appropriate compensation is performed on the working condition, so that the grating center is offset from the center point.

[0123] Under the same high voltage, the magnification of the last calibration or verification is used as a reference for the next calibration or verification.

[0124] Under different high voltages and beam conditions, the coordinates of the grating center position moved to the image center during the first calibration are recorded and updated in real time, and are transmitted to the first calibration or verification of the next high voltage and beam, as a position reference.

[0125] In some embodiments of the present application, the method used for verifying the imaging parameters according to the third grating image can refer to the method for calibrating the imaging parameters according to the second grating image.

[0126] The above will be described below with reference to a specific example. Figure 6 As shown in the accompanying drawings.

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

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

[0129] The initial position is a pre-set initial position, that is, the pre-set initial position of the grating sample when the calibration is performed for the first time. The MR is a magnification correction coefficient.

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

[0131] Determine whether to switch the high voltage or beam position according to the Param.

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

[0133] Move the sample stage to the point O coordinate, and if the point O does not exist, do not move.

[0134] Specifically, if the calibration is performed for the first time, since there is no parameter information about the center of the scanning electron microscope imaging field, the sample stage is not moved. If the calibration is not performed for the first time, since there is parameter information about the center of the scanning electron microscope imaging field, the sample stage can be moved based on the parameter information.

[0135] That is, if the current is the first calibration, the above-mentioned pre-set initial position is the initial position, if the current is not the first calibration, the above-mentioned pre-set initial position is the position based on the known scanning electron microscope imaging field center.

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

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

[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 demagnetization, automatic brightness, automatic focusing, automatic astigmatism, and other adjustments to make the image clear.

[0140] Adjust the magnification Mag according to the algorithm.

[0141] Wherein, the adaptive adjustment magnification is the adjustment of the number of gratings in the binary grating image to a pre-set range.

[0142] It should be noted that in the adaptive adjustment 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 according to the magnification calibrated for the previous working distance.

[0143] Calculate the movement of the grating center position to the image center according to the algorithm, and mark the coordinates of the center position moved in the first calibration under high voltage as O.

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

[0145] Detect the grating electric rotation angle according to the algorithm.

[0146] Adjust the magnification according to the algorithm to obtain the average size of the grating.

[0147] Obtain the focusing current under the working condition.

[0148] Statistical grating size, focusing current, and electric rotation angle under the working condition.

[0149] It is judged whether calibration or verification of all working conditions under the high voltage is completed. If not, the magnification Mag under the working condition is passed, and the step of moving the Z axis to the specified WD height is returned. If it is completed, it is judged whether calibration or verification is completed. If calibration is completed, the parameter set is written into the software, the lock is released, the step of moving the sample table to the point O coordinate is returned, and verification is started. If verification is completed, the step of switching the high voltage or the beam position according to the Param is returned, and calibration of the next high voltage is started.

[0150] The grating size under the working condition is the second grating size, i.e., the average grating size detected according to the algorithm.

[0151] After the second grating size, the focusing current, and the electric rotation angle of all preset calibration distances under one high voltage are obtained, the scanning electron microscope imaging verification can be performed based on the calibration parameters, the grating size, the electric rotation angle, and the working distance of clear imaging of the scanning electron microscope under different verification distances of the high voltage are 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 calibration distance is the working distance during calibration, and the verification distance is the working distance during verification.

[0153] The magnification Mag under the working condition is passed because only one magnification needs to be set when calibration or verification is performed for different working distances under the same voltage, and the magnifications of the remaining working distances are 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 application 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 the scanning electron microscope according to the first grating image, 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 imaging parameters that pass the verification. Thus, 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, which can ensure the accuracy of subsequent calibration and verification operations.

[0155] Further, the present application provides an electronic device.

[0156] Figure 7 is a structural block diagram of an electronic device of an embodiment of the present application.

[0157] As shown in Figure 7 , the electronic device 500 includes a processor 501 and a memory 503. The processor 501 and the memory 503 are connected, for example, via a bus 502. Optionally, the electronic device 500 can further include a transceiver 504. It should be noted that the transceiver 504 is not limited to one in actual applications, and the structure of the electronic device 500 does not constitute a limitation on the embodiments of the present application.

[0158] The processor 501 can be a CPU (Central Processing Unit, central processor), a general-purpose processor, a DSP (Digital Signal Processor, digital signal processor), an ASIC (Application Specific Integrated Circuit, application specific integrated circuit), an FPGA (Field Programmable Gate Array, field programmable gate array) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. It can implement or execute various exemplary logical blocks, modules and circuits described in combination with the present disclosure. The processor 501 can also be a combination of computing functions, such as one or more microprocessor combinations, combinations of DSP and microprocessor, etc.

[0159] The bus 502 can include a path for transmitting information between the above-mentioned components. The bus 502 can be a PCI (Peripheral Component Interconnect, peripheral component interconnect) bus or an EISA (Extended Industry Standard Architecture, extended industry standard architecture) bus, etc. The bus 502 can 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 figure, but it 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-mentioned embodiments of the present application. 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 realize the content shown in the foregoing method embodiments.

[0161] Among them, Figure 7 The electronic device 500 shown is only an example and should not limit the function and use range of the embodiments of the present application.

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

[0163] Further, the present application provides a scanning electron microscope imaging parameter calibration and verification system.

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

[0165] As shown in Figure 8 , the scanning electron microscope imaging parameter calibration and verification system 10 comprises the electronic device 500 described above.

[0166] The scanning electron microscope imaging parameter calibration and verification system of the embodiment of the present application can realize calibration and verification of the scanning electron microscope through the electronic device 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 list of ordered steps for implementing the logic function, which can be embodied in any computer readable medium for use by or in connection with an instruction execution system, apparatus or device, such as a computer-based system, a system including a processor or other system that can fetch the instructions from the instruction execution system, apparatus or device and execute the instructions, or in conjunction with these instruction execution systems, apparatus or devices. For the purpose of this specification, the "computer readable medium" can be any device that can contain, store, communicate, propagate or transport programs for use by or in connection with an instruction execution system, apparatus or device, or in conjunction with these instruction execution systems, apparatus or devices. More specific examples (non-exhaustive list) of computer readable medium include the following: electrical connections having one or more wires (electronic devices), portable computer diskette (magnetic devices), random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM or flash memory), fiber optic devices, and portable compact disk read only memory (CD ROM). In addition, the computer readable medium can even be paper or other suitable medium on which the program can be printed, because the program can be electronically obtained, for example, by optical scanning of the paper or other medium, followed by editing, interpreting or otherwise processing, if necessary, in other suitable ways, to be electronically obtained and then stored in the computer memory.

[0168] It should be understood that aspects of the application can be implemented in hardware, software, firmware or combinations thereof. In the embodiments described above, various steps or methods can be implemented, in part, or in whole, in software, or firmware that is stored in memory and executed by a suitable instruction execution system. If implemented in hardware, and in another embodiment, the hardware can include any or a combination of the following technologies, which are all well known in the art: discrete logic circuitry having logic gates for implementing logic functions upon an application of data signals, application specific integrated circuits having appropriate combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), or the like.

[0169] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0170] In the description of the specification, the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and cannot be understood as limiting the present application.

[0171] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0172] In the description of the present application, unless otherwise specified and limited, the terms "mounting", "connection", "linking", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements or interaction relationship of two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0173] In the present application, unless otherwise specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be directly above or obliquely above the first feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be directly below or obliquely below the first feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0174] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for calibrating and verifying imaging parameters of a scanning electron microscope, characterized in that, The method includes: Set the grating sample at the 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 based on 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 based on 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 based on the third grating image, and the verified imaging parameters are saved. The grating sample is a sample comprising multiple 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 includes: The target grating is determined from the plurality of gratings based on the first grating image; Move the grating sample until the center of the target grating is moved to the center of the imaging field of view; The step of calibrating the imaging parameters of the scanning electron microscope based on the second grating image includes: The grating sample is moved a second preset distance in a second preset direction, and the scanning electron microscope is controlled to image the grating sample to 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; The grating sample is moved a third preset distance in the second preset direction, and the scanning electron microscope is controlled to image the grating sample to obtain a sixth grating image; The electrical rotation angle of the scanning electron microscope is obtained based on the second grating image, the fifth grating image, the sixth grating image, and the size of the first grating. The imaging parameters of the scanning electron microscope are calibrated according to the electrical rotation angle; The calibration of the imaging parameters of the scanning electron microscope based on the electrical rotation angle includes: The maximum magnification is determined based on the second grating image, and the magnification of the scanning electron microscope is adjusted to the maximum magnification. The scanning electron microscope is controlled to image the grating sample to obtain a seventh grating image; The second grating size of the grating is obtained based on 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 electric rotation angle. The step of obtaining the electrical rotation angle of the scanning electron microscope based on the second grating image, the fifth grating image, the sixth grating image, and the first grating size includes: The set of first pixels in the second grating image, the set of second pixels in the fifth grating image, and the set of third pixels in the sixth grating image of the preset region on the grating sample are obtained. Obtain the first pixel distance set between the first pixel set and the corresponding pixels in the second pixel set, and obtain the second pixel distance set between the first pixel set and the corresponding pixels in the third pixel set; The target pixel distance in the first pixel distance set is determined based on the first grating size, and the reference angle is obtained based on the target pixel distance; Based on the first grating size, at least one pixel distance is selected from the second pixel distance set to obtain the candidate angle corresponding to the pixel distance; The electric rotation angle is determined based on the reference angle and the selected angle.

2. The scanning electron microscope imaging parameter calibration and verification method according to claim 1, characterized in that, The step of determining the target grating from the plurality of gratings based on the first grating image includes: The first raster image is binarized to obtain a binarized raster image; The gratings in the binarized grating image are identified; If the number of gratings in the binarized grating image is not within the preset range, the magnification of the scanning electron microscope is adjusted, and the process returns 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 binarized grating image is within the preset range. The target grating is determined based on the binarized grating image.

3. The scanning electron microscope imaging parameter calibration and verification method according to claim 2, characterized in that, The step of binarizing the first raster image to obtain a binarized raster image includes: The first raster image is converted into a grayscale image, and the grayscale value of each pixel in the grayscale image is obtained; A grayscale histogram is constructed based on the grayscale values, and a grayscale threshold is obtained based on the grayscale histogram. The grayscale image is binarized according to the grayscale threshold to obtain the binarized raster image.

4. The scanning electron microscope imaging parameter calibration and verification method according to claim 3, characterized in that, The process of identifying the gratings in the binarized grating image includes: A morphological opening operation is performed on the binarized raster image to obtain a denoised binarized image; Perform a pixel value inversion operation on the denoised binarized image to obtain a first inverted binarized image; For each pixel in the first inverted binarized image, the nearest distance between the pixel and the pixel with a value of 0 in the first inverted binarized image is obtained, and the pixel value of the pixel whose nearest distance is less than a preset distance threshold is set to 0 to obtain the second inverted binarized image; Identify the grating in the binary grating image based on the second inverted binarized image.

5. The scanning electron microscope imaging parameter calibration and verification method according to claim 2, characterized in that, Determining the target grating based on the binarized grating image includes: The grating closest to the center of the imaging field of view in the binarized grating image is identified as the target grating.

6. The scanning electron microscope imaging parameter calibration and verification method according to claim 1, characterized in that, Moving the grating sample until the center of the target grating is moved to the center of the imaging field of view includes: The grating sample is moved a first preset distance in a first preset direction, and the scanning electron microscope is controlled to image the grating sample to obtain a fourth grating image; The pixel movement distance of the grating sample in the image is obtained based on the fourth grating image and the first grating image; The grating center is moved to the imaging field of view center 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 imaging field of view center in the fourth grating image.

7. An electronic device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the computer program is executed by the processor, it implements the scanning electron microscope imaging parameter calibration and verification method according to any one of claims 1-6.

8. A scanning electron microscope imaging parameter calibration and verification system, characterized in that, Includes the electronic device according to claim 7.

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