Method and system for extracting contour of wafer electron microscope scanning image

Abstract

The invention provides a wafer electron microscope scanning image contour extraction method and system, and belongs to the field of semiconductors. The wafer electron microscope scanning image contour extraction method comprises the following steps: obtaining an original scanning image of a wafer, and preprocessing the original scanning image to obtain a target image; and performing edge detection on the target image to obtain a binary image. And extracting a contour from the binary image, and screening and complementing the extracted contour to obtain a binary image contour. And carrying out screening processing on the binary image contour, outputting a wafer image contour, and superposing the wafer image contour into the original scanning image to carry out graphical display. According to the method, after the steps of reading the original wafer electron microscope scanning image, preprocessing the original wafer electron microscope scanning image and the like are carried out, the wafer image contour is output and overlaid into the original wafer electron microscope scanning image for graphical display, and binary image contour information of the wafer can be rapidly and accurately obtained.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method and system for extracting the contour of a wafer electron microscope scanning image. Background Art

[0002] As semiconductor process nodes continue to shrink, especially as 40nm and below process nodes gradually become mainstream products, fast and accurate scanning and positioning of wafer defects has become an indispensable part of the semiconductor process. Fast and accurate positioning of wafer defects can facilitate related semiconductor design and manufacturing departments to quickly and accurately verify the rationality of layout design and manufacturing processes, and facilitate early discovery and resolution of potential problems in design and manufacturing processes, thereby greatly improving the efficiency of semiconductor layout design and manufacturing.

[0003] How to quickly and accurately find the location of wafer defects from massive wafer electron microscope scanning images is a problem that plagues the semiconductor industry. By extracting the contours of wafer electron microscope scanning images, it is easier to find the location of wafer defects. Electron microscope scanning images are affected by the parameters of the shooting machine and the conditions of the wafer itself. The images captured often contain a lot of noise, and even the images are relatively blurred. It is usually difficult to extract the accurate contour of the pattern by directly performing grayscale threshold separation.

[0004] It should be noted that the information disclosed in the background technology section of the invention is only intended to deepen the understanding of the general background technology of the invention, and should not be regarded as an admission or suggestion in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for extracting the contour of a wafer electron microscope scanning image, so as to solve the problem of how to extract the accurate contour of a pattern.

[0006] In order to solve the above technical problems, the present invention provides a method for extracting the contour of a wafer electron microscope scanning image, comprising:

[0007] Obtaining an original scanning image of the wafer, and preprocessing the original scanning image to obtain a target image;

[0008] Perform edge detection on the target image to obtain a binary image;

[0009] Extracting contours from the binary image, and performing screening and completion processing on the extracted contours to obtain binary image contours;

[0010] The binary image contour is screened and processed, and a wafer image contour is output, and the wafer image contour is superimposed on the original scanned image for graphical display.

[0011] Preferably, the step of acquiring the original scanned image of the wafer and preprocessing the original scanned image to acquire the target image comprises:

[0012] Scan the wafer with an electron microscope scanner and read the original scanned image of the wafer;

[0013] Performing image conversion on the original scanned image to convert the three-channel wafer color image into a single-channel wafer grayscale image;

[0014] Filter the wafer grayscale image to remove high-frequency noise in the original scanned image and retain the effective low-frequency image information in the wafer;

[0015] An image morphological operation is performed on the wafer grayscale image after filtering to obtain the target image.

[0016] Preferably, performing edge detection on the target image to obtain a binary image comprises:

[0017] Perform grayscale gradient calculation on the wafer grayscale image to obtain the gradient amplitude and direction;

[0018] Next, non-maximum suppression is performed on the wafer grayscale image;

[0019] Afterwards, the wafer grayscale image is double-thresholded to suppress weak edges and retain strong edges;

[0020] A binary image of the wafer grayscale image is obtained.

[0021] Preferably, the grayscale gradient calculation of the wafer grayscale image to obtain the gradient amplitude and direction includes:

[0022] The edge detection operator returns Gx in the horizontal direction and Gy in the vertical direction. The magnitude G and direction (expressed as an angle value) of the gradient are:

[0023]

[0024] where atan2(·) represents the arctan function with two parameters, where the direction of the gradient is perpendicular to the edge of the wafer target image.

[0025] Preferably, the non-maximum suppression of the wafer grayscale image comprises:

[0026] Based on the gradient angle, traverse the pixels in the target image to determine whether the current pixel is the maximum value of the surrounding pixels with the same gradient direction;

[0027] If the pixel is the maximum value in the positive / negative gradient direction, the pixel is retained; if not, the pixel is suppressed.

[0028] Preferably, the method for setting a double threshold value for a wafer grayscale image is as follows:

[0029]

[0030] Among them, σ and V mean They represent the threshold and grayscale mean of the wafer grayscale image respectively, σ is 0.25, maxVal is the first threshold, minVal is the second threshold, and the first threshold is greater than the second threshold.

[0031] Preferably, the step of setting a double threshold value for the target graphic contour value to suppress weak edges and retain strong edges further comprises:

[0032] Based on the gradient value of the pixel, the attribute of the edge of the wafer grayscale image is judged, wherein the gradient value of the pixel is the gradient amplitude of the pixel, and the specific steps are as follows:

[0033] If the gradient value of the current edge pixel is greater than or equal to maxVal, the current edge pixel is marked as a strong edge;

[0034] If the gradient value of the current edge pixel is between maxVal and minVal, the current edge pixel is marked as a virtual edge;

[0035] If the gradient value of the current edge pixel is less than or equal to minVal, the current edge pixel is suppressed;

[0036] If the virtual edge is connected to the strong edge, the edge is identified as an edge. If the virtual edge is not connected to the strong edge, the edge is a weak edge and is suppressed.

[0037] Preferably, extracting the contour from the binary image, and screening and completing the extracted contour to obtain the binary image contour comprises:

[0038] Performing opening and closing operations on the binary image to extract the contour of the binary image;

[0039] Screening the extracted contours to remove unreasonable contours;

[0040] The discontinuous contours are completed to obtain the binary image contours.

[0041] Preferably, the screening process of the binary image contour and outputting the wafer image contour, and superimposing the wafer image contour onto the original scanned image for graphical display comprises:

[0042] The size of the outline in the binary image outline is extracted, and the outline of the set size is removed to output the wafer image outline, and the target outline image is superimposed on the original scanned image for graphical display.

[0043] Based on the same inventive concept, the present invention also provides a system for extracting the contour of a wafer electron microscope scanning image, comprising:

[0044] The wafer image reading and preprocessing module is used to obtain the original scanned image of the wafer, and preprocess the original scanned image to obtain the target image;

[0045] A wafer image edge detection module, used to perform edge detection on the target image to obtain a binary image;

[0046] A wafer image contour extraction module, used to extract contours from the binary image, and perform screening and completion processing on the extracted contours to obtain binary image contours;

[0047] The wafer image outline output module is used to filter and process the binary image outline, output the wafer image outline, and superimpose the wafer image outline on the original scanned image for graphical display.

[0048] Compared with the prior art, the method for extracting the contour of a wafer electron microscope scanning image of the present invention has the following advantages:

[0049] The invention provides a method for extracting the contour of a wafer electron microscope scanning image. The method first reads the original image of the wafer electron microscope scanning, pre-processes it, and obtains a relatively smooth target image. Then, edge detection is performed on the pre-processed target image to obtain a binary image of the original image. Then, the binary image is opened and closed again to extract the contour of the binary image, and then the obtained binary image contour is post-processed, such as filtering out unreasonable contours and intermittent contour completion, and finally the processed binary image contour is output and superimposed on the original wafer electron microscope scanning image for graphical display. The method has been measured on 100,000 wafer electron microscope scanning images, and can quickly and accurately obtain the binary image contour information with an accuracy rate of 98.3%, thereby providing conditions for subsequent wafer defect scanning and positioning, and has very good application prospects.

[0050] The system for extracting the contour of a wafer electron microscope scanning image provided by the present invention and the method for extracting the contour of a wafer electron microscope scanning image provided by the present invention belong to the same inventive concept. Therefore, the system for extracting the contour of a wafer electron microscope scanning image provided by the present invention has at least all the advantages of the method for extracting the contour of a wafer electron microscope scanning image provided by the present invention, and can quickly and accurately obtain its binary image contour information with an accuracy rate of 98.3%, thereby providing conditions for subsequent wafer defect scanning and positioning, and has very good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a flow chart of a method for extracting the contour of a wafer electron microscope scanning image in one embodiment of the present invention;

[0052] Figure 2-a It is an original scanned image obtained by scanning a metal layer by an electron microscope in one embodiment of the present invention;

[0053] Figure 2-b In one embodiment of the present invention, Figure 2-a The image obtained after the original scanned image in is converted and filtered;

[0054] Figure 2-c It is a binary image obtained by edge detection of the wafer grayscale image;

[0055] Figure 2-d In one embodiment of the present invention, Figure 2-c The binary image shown is an image from which contours are extracted;

[0056] Figure 2-e In one embodiment of the present invention, Figure 2-d Wafer image profile of the image output in;

[0057] Figure 2-f In one embodiment of the present invention, Figure 2-e The final effect is the wafer image outline superimposed on the original scan image. DETAILED DESCRIPTION

[0058] In order to make the purpose, advantages and features of the present invention clearer, the following is a further detailed description of the method and system for extracting the contour of the wafer electron microscope scanning image proposed by the present invention in combination with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It should be understood that the drawings in the specification do not necessarily show the specific structure of the present invention in proportion, and the illustrative features used to illustrate certain principles of the present invention in the drawings in the specification will also adopt a slightly simplified drawing method. The specific design features of the present invention disclosed herein include, for example, specific dimensions, directions, positions and shapes, which will be determined in part by the specific environment to be applied and used. And, in the embodiments described below, sometimes the same figure mark is used in common between different drawings to represent the same part or a part with the same function, and its repeated description is omitted. In this specification, similar numbers and letters are used to represent similar items, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0059] 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.

[0060] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 representations of the above terms do 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. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0061] The core idea of ​​the present invention is to provide a method for extracting the contour of a wafer electron microscope scanning image, which can quickly and accurately obtain the contour of the electron microscope scanning image.

[0062] In order to realize the above idea, the present invention provides a method for extracting the contour of a wafer electron microscope scanning image. Figure 1 ,as well as Figure 2-a to Figure 2-fA specific implementation of a method for extracting the contour of a wafer electron microscope scanning image disclosed herein includes the following steps S1 to S4.

[0063] Step S1: Acquire an original scanned image of a wafer, and preprocess the original scanned image to acquire a target image.

[0064] Specifically, refer to Figure 1 As shown, the wafer original scan image is obtained through the wafer image reading and preprocessing module, and the original scan image is preprocessed to obtain the target image including:

[0065] First, the wafer is scanned by an electron microscope scanner to read the original scanned image of the wafer. The wafer is scanned by an electron microscope scanner to obtain a scanned image. At the same time, the original scanned image of the wafer is read by the wafer image reading module. The format of the original scanned image can be bmp, jpg, tif, png, etc.

[0066] Next, the original scanned image is converted to convert the three-channel wafer color image into a single-channel wafer grayscale image. This functional module can convert the image color format of the original scanned image to be obtained as needed, and convert the three-channel wafer color image into a single-channel wafer grayscale image, thereby removing redundant color information and retaining the main feature information of the image, which can speed up the subsequent wafer image processing speed.

[0067] Then, the wafer grayscale image is filtered to remove the high-frequency noise in the original scanned image and retain the effective low-frequency image information in the wafer. This functional module filters the wafer grayscale image to filter out the invalid high-frequency noise information in the original scanned image and retain the effective low-frequency image information in the wafer. Gaussian low-pass filtering, mean filtering, and wavelet filtering can be used for image filtering. Since the edge of the image is easily disturbed by noise, in order to avoid detecting erroneous edge information, it is usually necessary to filter the image to remove noise. The filtered wafer image can smooth some non-edge areas of the wafer image with weaker texture, so that a more accurate edge of the wafer image can be obtained.

[0068] During the filtering process, the weighted average value of the pixels around the pixel point of the wafer grayscale image is calculated through the filter to obtain the final filtering result. The size of the filter is also variable. The size of the Gaussian kernel of the Gaussian filter plays an important role in the effect of wafer image edge detection. The larger the kernel of the filter, the less sensitive the edge information of the wafer grayscale image is to noise. Generally speaking, choosing a 5×5 Gaussian kernel can meet most situations.

[0069] Finally, the wafer grayscale image after filtering is subjected to image morphological operations to obtain the target image. This functional module performs image morphological operations on the filtered wafer grayscale image, such as expansion, contraction, opening, closing, etc., to remove burrs in the wafer grayscale image, fill tiny holes, etc., to obtain a smoother target image, in preparation for the next step of improving the edge detection accuracy of the wafer grayscale image.

[0070] Step S2: Perform edge detection on the target image to obtain a binary image.

[0071] Specifically, refer to Figure 1 As shown, the target image is edge detected by the wafer image edge detection module to obtain the binary image of the original scanned image. The function of this module is mainly to perform edge detection operations on the wafer grayscale image after color conversion, filtering and morphological processing in the wafer image reading and preprocessing module, find the real edge of the pattern in the wafer grayscale image, and prepare for the next step of extracting the pattern contour of the wafer grayscale image. Since the wafer grayscale image contains a lot of noise, it is difficult to obtain the effective edge information of the pattern in the wafer grayscale image even after filtering and using a simple threshold separation method. By performing edge detection on the wafer grayscale image, a more ideal edge binary image of the pattern in the wafer grayscale image can be obtained, which can provide conditions for the next processing module to extract the contour information of the wafer grayscale image.

[0072] There are many image edge detection operators that can be used for image edge detection, such as the Scharr operator, Sobel operator, and Laplacian operator. In essence, they all calculate the gradient of the image grayscale image and select the position with the largest gradient value change as the edge of the image. This method uses the Canny edge detection method to detect the edge of the wafer pattern on the wafer grayscale image. The advantage of the Canny edge detection method is that it can perform non-maximum suppression and determine strong edges and weak edges through dual threshold settings, filter out weak edges, and retain strong edges. The Canny edge detection method needs to determine the dual threshold range through trial and error based on the actual wafer grayscale image.

[0073] The Canny edge detection process of the wafer grayscale image is as follows:

[0074] ① Wafer grayscale image gradient calculation

[0075] The direction of the calculated gradient is perpendicular to the direction of the edge of the wafer grayscale image. The edge detection operator returns Gx in the horizontal direction and Gy in the vertical direction. The magnitude G and direction (expressed as an angle value) of the gradient are:

[0076]

[0077] Where atan2(·) represents the arctan function with two parameters.

[0078] The direction of the gradient is always perpendicular to the edge of the wafer grayscale image, and usually the nearest value is horizontal (left, right), vertical (upper, lower), diagonal (upper right, upper left, lower left, lower right), etc. 8 different directions. Therefore, when calculating the gradient, we will get two values: the amplitude and angle (representing the direction of the gradient) of the wafer grayscale image gradient.

[0079] ② Non-maximum suppression of wafer grayscale images

[0080] After obtaining the amplitude and direction of the wafer grayscale image gradient, traverse the pixel points in the image and remove all non-edge points. In the specific implementation, traverse the pixel points one by one to determine whether the current pixel point is the maximum value with the same gradient direction among the surrounding pixel points, and decide whether to suppress the point based on the judgment result. From the above description, it can be seen that this step is the process of edge refinement. For each wafer grayscale image pixel point:

[0081] (1) If the pixel is the local maximum in the positive / negative gradient direction, the pixel is retained;

[0082] (2) If the pixel is not a local maximum in the positive / negative gradient direction, the pixel is suppressed (i.e., returned to zero).

[0083] ③Dual threshold setting for wafer grayscale image

[0084] After completing the above steps, the strong edges in the wafer grayscale image are already in the currently acquired edge image. However, some virtual edges may also be in the edge image. These virtual edges may be generated by real images or by noise. For the latter, they must be eliminated. Set two thresholds, one of which is the first threshold maxVal, and the other threshold is the second threshold minVal, and the first threshold is greater than the second threshold. According to the relationship between the gradient value (referring to the gradient amplitude, the same below) of the edge pixel of the current wafer grayscale image and the two thresholds, the attributes of the edge of the wafer grayscale image are judged. The specific steps are:

[0085] (1) If the gradient value of the current edge pixel is greater than or equal to maxVal, the current edge pixel is marked as a strong edge.

[0086] (2) If the gradient value of the current edge pixel is between maxVal and minVal, the current edge pixel is marked as a virtual edge and needs to be retained.

[0087] (3) If the gradient value of the current edge pixel is less than or equal to minVal, the current edge pixel is suppressed.

[0088] In the above process, we get the virtual edge of the wafer grayscale image, which needs to be further processed. Generally, we can determine which case the virtual edge belongs to by judging whether the virtual edge is connected to the strong edge. The specific situation is as follows:

[0089] (1) When the virtual edge of the wafer grayscale image is connected to the strong edge, the marked weak edge is processed as an edge.

[0090] (2) If the virtual edge of the wafer grayscale image is not connected to the strong edge, the marked edge is identified as a weak edge and is suppressed.

[0091] Regarding the setting range of the dual thresholds maxVal and minVal of the wafer grayscale image, one method is to obtain it by trial and error, and another method is to determine it according to the following formula:

[0092] minVal=Max[0,(1-σ)V mean ],max Val=Min[255,(1+σ)V mean ] (2)

[0093] Among them, σ and V mean Represent the threshold and grayscale mean of the wafer grayscale image, and σ is usually 0.25, which can meet most of the situations. The advantage of this method is that only one threshold σ needs to be set to complete the edge extraction of the wafer grayscale image. This paper adopts this method.

[0094] ④ Binary edge image extraction of wafer grayscale image

[0095] After the above steps, the wafer grayscale image has been converted into a binary wafer image containing wafer image edge information, which can be used as the input of the wafer image contour extraction module to further extract the contour of the wafer image.

[0096] Step S3: extracting contours from the binary image, and performing screening and completion processing on the extracted contours to obtain binary image contours.

[0097] Specifically, refer to Figure 1 As shown, the wafer image contour extraction module is used to extract the contour from the binary image, and the extracted contour is screened and completed to obtain the binary image contour.

[0098] The function of this module is to extract the outline of the binary image after opening and closing operations based on the binary image extracted by the wafer image edge detection module. Then, the obtained binary image outline is intermittently completed, and finally the binary image outline is sent to the wafer image outline output module.

[0099] Since the actual wafer grayscale image has low image quality, such as too much image noise or even blurred images, after the above edge processing, the pattern contour is discontinuous, so morphological operations must be performed again, such as opening and closing operations, to enhance the continuity of the contour. Depending on the situation, contour completion operations can also be performed to complete the discontinuous contour into a continuous contour. In this way, it can be ensured that the contour information can be extracted from most wafer grayscale images.

[0100] Step S4: screening the binary image contour and outputting the wafer image contour, and superimposing the wafer image contour onto the original scanned image for graphical display.

[0101] Specifically, refer to Figure 1 As shown, the binary image contour is output by the wafer image contour extraction module and superimposed on the original scanned image for graphical display.

[0102] This module performs contour screening based on the binary image contour information output by the wafer image contour extraction module, removes contours of a set size, and thereby removes unreasonable contours that are too small or too large, outputs the final wafer image contour, and superimposes it on the original scanned image for graphical display.

[0103] This method has been tested on 100,000 wafer electron microscope scanning images and can quickly and accurately obtain binary image contour information with an accuracy of 98.3%, thus providing conditions for further scanning and positioning of subsequent wafer defects.

[0104] Ginseng Figure 2-a to Figure 2-f As shown, the specific process of the method for extracting the contour of the wafer electron microscope scanning image proposed in this embodiment is described below by taking the electron microscope scanning image of a metal layer wafer of a certain product as an example:

[0105] Basic parameters of wafer electron microscope scanning image:

[0106] Original scan image size: 2048um*2048um

[0107] Original scanned image format: BMP

[0108] Original scanned image size: 4.1M

[0109] Original scan image resolution: 1nm / Pixel

[0110] The main extraction process of wafer electron microscope scanning image contour is as follows:

[0111] 1) Original scanned image reading and preprocessing

[0112] First, the wafer electron microscope scanning image is read to obtain the wafer original scanning image. Then the wafer original scanning image is converted from color image to grayscale image, and finally a Gaussian filter is used to filter out the high-frequency noise in the image, and the filter selects a 5×5 Gaussian kernel. Figure 2-a The original scanning image of a metal layer obtained by electron microscope scanning is given. Figure 2-b The image obtained after conversion and filtering of the original scanned image is given.

[0113] 2) Wafer grayscale image edge detection

[0114] The filtered wafer grayscale image obtained in the Canny extraction step 1) is used, and the setting range of the dual thresholds maxVal and minVal is calculated according to formula (2), and the value is 0.25. Figure 2-c The binary image of the wafer is given after edge detection of the wafer grayscale image.

[0115] 3) Wafer image contour extraction

[0116] The binary image obtained in step 2) is subjected to opening and closing operations and intermittent contour completion (as appropriate) to extract the contour of the binary image, and the following is obtained: Figure 2-d The image shown in .

[0117] 4) Wafer image profile output

[0118] The contours of the binary image obtained in step 3) are screened to remove unreasonable small or large contours, and the final wafer image contour is output. Since the metal layer appears as a groove on the wafer, only the inner contour needs to be extracted to obtain the following: Figure 2-e Image shown. Figure 2-f The final effect of superimposing the wafer image contour onto the original scanned image is given. It can be seen that after the above four steps, this method can well extract the contour of the wafer electron microscope scanned original image, so it is a very effective method.

[0119] In summary, the above embodiments provide detailed descriptions of different configurations of the method and system for extracting the contour of a wafer electron microscope scanning image. Of course, the above description is only a description of a preferred embodiment of the present invention, and is not any limitation to the scope of the present invention. The present invention includes but is not limited to the configurations listed in the above implementations. Those skilled in the art can draw inferences based on the contents of the above embodiments. Any changes and modifications made by those of ordinary skill in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for extracting the contour of a wafer electron microscope scanning image, characterized in that: include: Obtaining an original scanning image of the wafer, and preprocessing the original scanning image to obtain a target image; Perform edge detection on the target image to obtain a binary image; Extracting contours from the binary image, and performing screening and completion processing on the extracted contours to obtain binary image contours; The binary image contour is screened and processed, and a wafer image contour is output, and the wafer image contour is superimposed on the original scanned image for graphical display.

2. The method for extracting the contour of a wafer electron microscope scanning image according to claim 1, characterized in that: The step of obtaining the original scanned image of the wafer and preprocessing the original scanned image to obtain the target image includes: Scan the wafer with an electron microscope scanner and read the original scanned image of the wafer; Performing image conversion on the original scanned image to convert the three-channel wafer color image into a single-channel wafer grayscale image; Filter the wafer grayscale image to remove high-frequency noise in the original scanned image and retain the effective low-frequency image information in the wafer; An image morphological operation is performed on the wafer grayscale image after filtering to obtain the target image.

3. The method for extracting the contour of a wafer electron microscope scanning image according to claim 2, characterized in that: The performing edge detection on the target image to obtain a binary image comprises: Perform grayscale gradient calculation on the wafer grayscale image to obtain the gradient amplitude and direction; Next, non-maximum suppression is performed on the wafer grayscale image; Afterwards, the wafer grayscale image is double-thresholded to suppress weak edges and retain strong edges; A binary image of the wafer grayscale image is obtained.

4. The method for extracting the contour of a wafer electron microscope scanning image according to claim 3, characterized in that: The grayscale gradient calculation of the wafer grayscale image to obtain the gradient amplitude and direction includes: The edge detection operator returns Gx in the horizontal direction and Gy in the vertical direction. The magnitude G and direction (expressed as an angle value) of the gradient are: where atan2(·) represents the arctan function with two parameters, where the direction of the gradient is perpendicular to the edge of the wafer target image.

5. The method for extracting the contour of a wafer electron microscope scanning image according to claim 4, characterized in that: The non-maximum suppression of the wafer grayscale image comprises: Based on the gradient angle, traverse the pixels in the target image to determine whether the current pixel is the maximum value of the surrounding pixels with the same gradient direction; If the pixel is the maximum value in the positive / negative gradient direction, the pixel is retained; if not, the pixel is suppressed.

6. The method for extracting the contour of a wafer electron microscope scanning image according to claim 5, characterized in that: The method for setting a double threshold value for a wafer grayscale image is as follows: minVal=Max[0,(1-σ)V mean ], maxVal=Min[255,(1+σ)V mean ] (2) Among them, σ and V mean They represent the threshold and grayscale mean of the wafer grayscale image respectively, σ is 0.25, maxVal is the first threshold, minVal is the second threshold, and the first threshold is greater than the second threshold.

7. The method for extracting the contour of a wafer electron microscope scanning image according to claim 6, characterized in that: The step of setting a double threshold value for the target graphic contour value to suppress weak edges and retain strong edges further comprises: Based on the gradient value of the pixel, the attribute of the edge of the wafer grayscale image is judged, wherein the gradient value of the pixel is the gradient amplitude of the pixel, and the specific steps are as follows: If the gradient value of the current edge pixel is greater than or equal to maxVal, the current edge pixel is marked as a strong edge; If the gradient value of the current edge pixel is between maxVal and minVal, the current edge pixel is marked as a virtual edge; If the gradient value of the current edge pixel is less than or equal to minVal, the current edge pixel is suppressed; If the virtual edge is connected to the strong edge, the edge is identified as an edge. If the virtual edge is not connected to the strong edge, the edge is a weak edge and is suppressed.

8. The method for extracting the contour of a wafer electron microscope scanning image according to claim 1, characterized in that: The extracting of the contour from the binary image, and screening and completing the extracted contour to obtain the binary image contour comprises: Performing opening and closing operations on the binary image to extract the contour of the binary image; Screening the extracted contours to remove unreasonable contours; The discontinuous contours are completed to obtain the binary image contours.

9. The method for extracting the contour of a wafer electron microscope scanning image according to claim 1, characterized in that: The filtering and processing of the binary image contour and outputting the wafer image contour, and superimposing the wafer image contour onto the original scanned image for graphical display includes: The size of the outline in the binary image outline is extracted, and the outline of the set size is removed to output the wafer image outline, and the target outline image is superimposed on the original scanned image for graphical display.

10. A wafer electron microscope scanning image contour extraction system, characterized in that: include: The wafer image reading and preprocessing module is used to obtain the original scanned image of the wafer, and preprocess the original scanned image to obtain the target image; A wafer image edge detection module, used to perform edge detection on the target image to obtain a binary image; A wafer image contour extraction module, used to extract contours from the binary image, and perform screening and completion processing on the extracted contours to obtain binary image contours; The wafer image outline output module is used to filter and process the binary image outline, output the wafer image outline, and superimpose the wafer image outline on the original scanned image for graphical display.

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