Wafer back defect detection method, device and equipment and storage medium

Abstract

The invention relates to a wafer back defect detection method, device and equipment and a storage medium, and is applied to the field of wafer defect detection, and the method comprises the steps: determining a target focal length sequence of a microscope lens at a to-be-detected point according to the position of the to-be-detected point, and obtaining a target image sequence corresponding to the to-be-detected point according to the target focal length sequence; performing image fusion processing on each image in the target image sequence to obtain a target clear image of the to-be-detected point; and obtaining target clear images of all the to-be-detected points on the back surface of the to-be-detected wafer, and obtaining a defect detection result of the back surface of the to-be-detected wafer according to the color gradation difference of the target clear images of all the to-be-detected points. The wafer back defect detection method has the technical effects that the wafer image fusion time is saved, and the wafer back defect detection efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of wafer defect detection, and in particular to a method, device, equipment and storage medium for wafer back side defect detection. Background Art

[0002] In the semiconductor wafer manufacturing process, the processing quality of the wafer directly determines the yield and quality of subsequent chip products. The surface of the wafer contains the circuits of the chip, etc. Affected by various factors such as process and raw materials, the surface defects of the wafer are usually very small and have diverse morphological structures. Therefore, it is usually necessary to obtain multiple high-precision and clear wafer images to detect defects on the surface of the wafer. At the same time, during the wafer manufacturing process, there may also be scratches, corrosion and other defects on the back of the wafer. Scratches, corrosion and other defects on the back may cause cracks in the chip. Therefore, the defects on the back of the wafer are detected to ensure the quality of the wafer and improve the wafer yield.

[0003] Defect detection on the back of wafers usually involves collecting multiple images at a single detection point for defect detection. However, the back of the wafer does not involve complex circuits, etc., that is, defect detection on the back of the wafer does not need to detect short circuits, open circuits, etc. of the circuits, but only needs to detect whether there are defects such as scratches. If there are too many wafer images collected at a single point, it will take too long to capture an image at a single detection point, which may affect the efficiency of wafer detection and lead to reduced wafer detection efficiency. Summary of the invention

[0004] In order to help solve the problem that a large number of wafer images are collected at a single point, resulting in too long time to capture an image at a single inspection point, thereby affecting the efficiency of wafer inspection and causing reduced wafer inspection efficiency, the present application provides a wafer back side defect detection method, device, equipment and storage medium.

[0005] In a first aspect, the present application provides a method for detecting defects on the back side of a wafer, which adopts the following technical solution: the method is applied to an automatic optical detection system for defects on the back side of a wafer, the automatic optical detection system for defects on the back side of a wafer comprises a microscope lens, the microscope lens is used to collect an image of the back side of a wafer to be detected, and the focal length of the microscope lens is adjustable, and the method comprises:

[0006] Determine the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquire the target image sequence corresponding to the point to be detected according to the target focal length sequence;

[0007] Performing image fusion processing on each image in the target image sequence to obtain a clear target image of the point to be detected;

[0008] Obtain a target clear image of all the points to be detected on the back side of the wafer to be detected, and obtain a defect detection result on the back side of the wafer to be detected based on the color scale difference of the target clear image of all the points to be detected.

[0009] In a specific possible implementation manner, determining the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquiring the target image sequence corresponding to the point to be detected according to the target focal length sequence comprises:

[0010] Applied to any starting point to be inspected on the back side of the wafer to be inspected, the starting focal length sequence of the microscope lens is determined according to the acquired minimum focusing distance of the microscope lens and the acceptable height difference of the wafer to be inspected;

[0011] Acquire a starting image sequence collected by the microscope lens at the starting point to be detected, wherein the starting image sequence is compatible with the starting focal length sequence;

[0012] The clarity of each image in the starting image sequence is calculated based on a preset image clarity evaluation algorithm, a target focal length sequence is determined according to a preset sequence length, and an image subsequence with the highest clarity score is determined as a target image sequence.

[0013] In a specific possible implementation manner, determining the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquiring the target image sequence corresponding to the point to be detected according to the target focal length sequence comprises:

[0014] Applied to any non-starting point to be inspected on the back side of the wafer to be inspected, the target focal length of the current point to be inspected is determined according to the target image sequence of the previous point to be inspected;

[0015] Acquire a first image captured by the microscope lens at the current point to be detected, wherein the first image is adapted to the target focal length;

[0016] The clarity of the first image is calculated based on a preset image clarity evaluation algorithm, the clarity of the first image is compared with a first preset threshold, and the target image sequence at the current position is determined according to the comparison result.

[0017] In a specific possible implementation manner, comparing the clarity of the first image with a first preset threshold, and determining the target image sequence at the current position according to the comparison result includes:

[0018] If the clarity value of the first image is within a first preset threshold range, setting the first image as a target image sequence;

[0019] If the clarity value of the first image is not within a first preset threshold range, determining an initial focal length subsequence according to the target focal length;

[0020] Acquire an initial image subsequence collected by the microscope lens at the current point to be detected, wherein the initial image subsequence is compatible with the initial focal length subsequence;

[0021] The clarity of each image in the initial image subsequence is calculated based on a preset image clarity evaluation algorithm. If the clarity value of each image is within a second preset threshold range, the initial image subsequence is determined to be the target image sequence of the current point to be detected.

[0022] In a specific possible implementation scheme, determining the target focal length of the current point to be detected based on the target image sequence of the previous detection point includes:

[0023] Calculating the clarity of each image in the target image sequence of the previous detection point according to a preset image clarity evaluation algorithm, and determining the focal length corresponding to the image with the highest clarity;

[0024] The height difference between the current point to be detected and the last detected point is calculated, and the target focal length of the current point to be detected is determined according to the height difference and the focal length corresponding to the image with the highest definition at the last detected point.

[0025] In a specific possible implementation scheme, obtaining the defect detection result of the back side of the wafer to be detected according to the color scale difference of the target clear image of all the points to be detected includes:

[0026] Determine whether there is a color scale difference in the target clear image of all points to be detected;

[0027] If the target clear images of all the points to be inspected do not have color scale differences, it is determined that there is no defect on the back side of the wafer to be inspected;

[0028] Otherwise, it is determined that there is a defect on the back side of the wafer to be inspected.

[0029] In a specific implementation manner, the preset sequence length is at least 2.

[0030] In a second aspect, the present application provides a wafer back side defect detection device, which adopts the following technical solution: the device is applied to an automatic optical detection system for wafer back side defects, the automatic optical detection system for wafer back side defects includes a microscope lens, the microscope lens is used to collect an image of the back side of the wafer to be detected, the focal length of the microscope lens is adjustable, and the device includes:

[0031] A target image determination module, used to determine a target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and to obtain a target image sequence corresponding to the point to be detected according to the target focal length sequence;

[0032] A clear image generation module, used for performing image fusion processing on each image in the target image sequence to obtain a clear target image of the point to be detected;

[0033] The back defect judgment module is used to obtain the target clear image of all the points to be detected on the back of the wafer to be detected, and obtain the defect detection result of the back of the wafer to be detected according to the color scale difference of the target clear image of all the points to be detected.

[0034] In a third aspect, the present application provides a computer device, which adopts the following technical solution: it includes a memory and a processor, and the memory stores a computer program that can be loaded by the processor and execute any of the above-mentioned wafer back side defect detection methods.

[0035] In a fourth aspect, the present application provides a computer-readable storage medium, which adopts the following technical solution: storing a computer program that can be loaded by a processor and execute any of the above-mentioned wafer back side defect detection methods.

[0036] In summary, this application has the following beneficial technical effects:

[0037] Different optimized target focal length sequences are obtained according to different positions of the points to be detected, and a target image sequence with higher clarity is obtained according to the target focal length sequence, thereby reducing the number of target images obtained and the number of fused images, and each image in the target image sequence is fused, thereby saving the processing time of wafer image fusion, and further improving the efficiency of wafer image fusion and wafer back side defect detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a flow chart of a wafer backside defect detection method in an embodiment of the present application;

[0039] Figure 2 is a schematic diagram of a wafer back side image having a color scale difference in an embodiment of the present application;

[0040] Figure 3 is a schematic diagram of a wafer backside defect detection device in an embodiment of the present application;

[0041] Figure 4 It is a schematic diagram used to embody a computer device in an embodiment of the present application.

[0042] Reference numerals: 301, target image determination module; 302, clear image generation module; 303, back defect determination module. DETAILED DESCRIPTION

[0043] The following combination Figure 1-Figure 4 This application is described in further detail.

[0044] The embodiment of the present application discloses a method for detecting defects on the back side of a wafer, which is applied to an automatic optical detection system for defects on the back side of a wafer. The method can realize efficient detection of defects on the back side of a wafer, save the time for acquiring wafer images and the time consumed in the wafer image fusion process, thereby improving the efficiency of wafer defect detection. In the semiconductor wafer manufacturing process, the processing quality of the wafer directly determines the yield and quality of subsequent chip products. The surface of the wafer contains the circuits of the chip, etc. Affected by various factors such as process and raw materials, the surface defects of the wafer are usually very small and have various morphological structures. Therefore, the surface defects of the wafer usually require the acquisition of multiple high-precision and clear wafer images to detect the defects on the surface of the wafer. At the same time, in the wafer manufacturing process, there may also be defects such as scratches and corrosion on the back side of the wafer. The scratches and corrosion on the back side may cause cracks in the chip. Therefore, the defects on the back side of the wafer are detected to ensure the quality of the wafer and improve the yield of the wafer.

[0045] Defect detection on the back of a wafer usually involves collecting multiple images at a single detection point for defect detection. However, the back of the wafer does not involve complex circuits, etc., that is, defect detection on the back of the wafer does not need to detect short circuits, open circuits, etc. of the circuits, but only needs to detect whether there are defects such as scratches. If there are many wafer images collected at a single point, it will take too long to capture an image at a single detection point, which may affect the efficiency of wafer detection and reduce the efficiency of wafer detection. In order to help improve the efficiency of defect detection on the back of a wafer, the present application provides a defect detection method for the back of a wafer.

[0046] Reference Figure 1 , the method comprises the following steps:

[0047] S10, determining a target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquiring a target image sequence corresponding to the point to be detected according to the target focal length sequence.

[0048] Specifically, the wafer back defect detection method is applied to the automatic optical detection system of wafer back defects. The wafer back defect detection needs to be detected based on the image of the back of the wafer acquired. In the embodiment of the present application, the way of acquiring the wafer back image is based on the microscope lens. During defect detection, a number of points to be detected will be set on the back of the wafer in advance, and the microscope lens will perform image acquisition operations on each point to be detected in sequence to obtain a clear image for final defect detection. Wafer back defect detection is a continuous process. The points to be detected will have a starting point to be detected and other non-starting points to be detected. The target focal length sequence corresponding to different detection points is determined for the starting point to be detected and the non-starting point to be detected. The number of focal lengths in the determined target focal length sequence is an optimized number, and then the target image sequence corresponding to the target focal length sequence of the microscope lens at the position of the point to be detected is obtained, wherein the target image sequence contains multiple high-definition continuous wafer back images.

[0049] S20, performing image fusion processing on each image in the target image sequence to obtain a clear target image of the point to be detected.

[0050] Specifically, multiple high-definition continuous wafer back side images in the determined target image sequence are subjected to image fusion processing, thereby generating a high-definition fused image of the wafer back side to obtain a final target clear image, thereby improving the quality of the fused image.

[0051] S30, obtaining a target clear image of all the points to be inspected on the back side of the wafer to be inspected, and obtaining a defect detection result of the back side of the wafer to be inspected according to the color scale difference of the target clear image of all the points to be inspected.

[0052] Specifically, the back of a wafer to be inspected contains several inspection points. The image of each inspection point is acquired and image fusion is performed through the microscope lens in the above manner to obtain a clear target image of each inspection point. The color scale difference in the clear target image of each inspection point is used to determine whether there is a defect on the back of the wafer to be inspected. Since the structure of the back of the wafer is relatively simple and does not involve delicate parts such as circuits and components, it is only necessary to detect whether there are scratches, dirt, foreign matter, etc. on the back of the wafer. When there are scratches, dirt, foreign matter, etc. on the back of the wafer, the image of the back of the wafer obtained will have a color scale difference. Refer to Figure 2 ,Therefore, the defect detection on the back side of the wafer can be realized simply and efficiently by judging the color gradation difference.

[0053] In the present application scheme, different optimized target focal length sequences are obtained according to the different positions of the points to be detected, and a target image sequence with higher clarity is obtained according to the target focal length sequence, thereby reducing the number of target images acquired and the number of fused images, and each image in the target image sequence is fused, thereby saving the processing time of wafer image fusion, and further improving the efficiency of wafer image fusion and wafer back side defect detection.

[0054] In one embodiment, the step of determining the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquiring the target image sequence corresponding to the point to be detected according to the target focal length sequence can be specifically performed as follows:

[0055] Applied to any starting point to be detected on the back of the wafer to be detected, the starting focal length sequence of the microscope lens is determined according to the minimum focusing distance of the microscope lens obtained and the acceptable height difference of the wafer to be detected. Specifically, in the embodiment of the present application, the microscope lens used has a minimum focusing distance, and the user can set the minimum focusing distance of the liquid microscope lens in advance; at the position of any starting point to be detected on the back of the wafer to be detected, the system determines the starting focal length sequence of the microscope lens according to the minimum focusing distance of the microscope lens obtained and the acceptable height difference of the wafer. Among them, the number of images of the back side of the wafer obtained according to the minimum focusing distance of the microscope lens is the maximum number of images; in addition, the number of images of the back side of the wafer obtained is related to the acceptable height difference of the wafer, and the acceptable height difference of the wafer is related to the warping amplitude of the wafer. During the wafer manufacturing process, the wafer may have a certain warping amplitude. Generally, the warping amplitude of the wafer is ±5mm, and the acceptable height difference of the wafer is 10mm. At this time, the number of starting focal length sequences of the microscope lens is 10mm divided by the minimum focusing distance of the microscope lens. Assuming that the minimum focusing distance of the microscope lens is 0.4mm, there are 25 continuous focal lengths in the final starting focal length sequence.

[0056] After determining the starting focal length sequence, obtain the starting image sequence collected by the microscope lens at the starting point to be detected, wherein the starting image sequence is adapted to the starting focal length sequence. Specifically, obtain the corresponding starting image sequence according to the determined starting focal length sequence. For example, assuming that the minimum focusing distance of the microscope lens is 0.4 mm, the wafer warpage amplitude is ±5 mm, and the acceptable height difference of the wafer is 10 mm, the final starting focal length sequence has 25 continuous focal lengths, and the microscope lens obtains the corresponding starting image sequence according to the determined 25 focal length sequences.

[0057] Afterwards, the clarity of each image in the starting image sequence is calculated based on a preset image clarity evaluation algorithm, wherein the image clarity evaluation algorithm can directly use an existing algorithm to evaluate the clarity of each image and give a corresponding score. Then, the target focal length sequence is determined according to the preset sequence length, and the image subsequence with the highest clarity score is determined as the target image sequence; for example, if the image sequence length is set to 5, then 5 consecutive images with high clarity need to be screened out from the image subsequence, and the screening method can be to sort the image sequence according to clarity and determine the image subsequence with the highest clarity score as the starting target image subsequence. Considering that there are blurred and clear images in the maximum number of collected starting image sequences, and in the image fusion process, blurred images are difficult to improve the clarity of the fused image, and at the same time, the image fusion processing time may be increased, thereby reducing the efficiency of image fusion. Therefore, the starting target image subsequence is determined according to the clarity sorting, and the number of images is reduced, thereby saving the processing time of image fusion, improving the efficiency of image fusion, and thus improving the efficiency of wafer inspection.

[0058] It should be noted that in the embodiment of the present application, the preset sequence length, that is, the number of the starting target image subsequences, is at least 2. During the wafer manufacturing process, the wafer is not absolutely flat and may have a certain warping amplitude. Considering the warping amplitude of the wafer, the number of continuous clear images is determined to be at least 2 to ensure that a clear image can be captured at a detection point with a slope, and wafer back defect detection can be performed, thereby improving the defect detection rate on the back of the wafer.

[0059] In the present application scheme, after acquiring a maximum number of wafer back side images, a starting target image subsequence with higher clarity is determined based on the image clarity. The number of starting target image subsequences can be determined by the user, thereby reducing the number of wafer back side image acquisition. The reduction in the number of images saves processing time for wafer image fusion, thereby improving the efficiency of wafer image fusion and wafer back side defect detection.

[0060] In one embodiment, the step of determining the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquiring the target image sequence corresponding to the point to be detected according to the target focal length sequence can be specifically performed as follows:

[0061] Since backside defect detection is a continuous process, after determining the position of the starting point to be detected for wafer backside defect detection, there are several non-starting points to be detected that need to be detected. Therefore, for any non-starting point to be detected on the back of the wafer to be detected, the target focal length of the current point to be detected is determined based on the target image sequence of the previous detection point; specifically, the clarity of each image in the target image subsequence of the previous detection point is calculated based on the preset image clarity evaluation algorithm, and the focal length corresponding to the image with the highest clarity is determined; the height difference between the current position and the previous position is calculated, and the target focal length of the current position is determined based on the height difference and the focal length corresponding to the image with the highest clarity at the previous position. For example, assuming that the current position of the point to be detected is a non-starting position of the point to be detected that follows the starting detection point, the previous detection point of the current point to be detected can be understood as the starting detection point, and then the target focal length of the current point to be detected is determined according to the starting target image subsequence obtained at the starting detection point; the determination method can be to first calculate the clarity of each image in the starting target image subsequence through a clarity evaluation algorithm, and determine the focal length corresponding to the image with the highest clarity, and then calculate the height difference between the current position and the starting position, and on the basis of the focal length corresponding to the determined image with the highest clarity, increase or decrease the focal length according to the calculated height difference to obtain the target focal length of the current position.

[0062] After determining the target focal length of the current detection point, the first image that is collected by the microscope lens at the current detection point and is adapted to the target focal length is acquired according to the target focal length. Finally, the clarity of the first image is calculated based on a preset image clarity evaluation algorithm, the clarity of the first image is compared with a first preset threshold, and the target image sequence at the current position is determined according to the comparison result.

[0063] If the clarity value of the first image is within the first preset threshold range, the first image is set as the target image sequence. It can also be understood that if the clarity of the acquired first image meets the requirements, the first image is a clear image. The target image sequence contains only one clear image, namely the first image, which reduces the number of images and saves image fusion time, thereby improving the efficiency of defect detection. If the clarity value of the first image is not within the first preset threshold range, the initial focal length subsequence is determined according to the target focal length to obtain a target image sequence with higher clarity.

[0064] When the clarity of the first image is not within the threshold range, the step of acquiring an image sequence of a preset sequence length according to the target focal length of the current point to be detected for image fusion may include: first, determining the initial focal length subsequence of the current point to be detected according to the target focal length, and the determination method may be selected according to the minimum focusing distance of the microscope lens near the target focal length, for example, selecting the target focal length and a continuous focal length sequence of the target focal length ± the minimum focusing distance to obtain an initial focal length subsequence of a preset length, and the preset length is at least set to 2; after determining the initial focal length subsequence, acquiring the initial image subsequence collected by the microscope lens at the current point to be detected, the initial image subsequence is adapted to the initial focal length subsequence, wherein the length of the acquired initial image subsequence is the preset length, which is consistent with the number of the initial target image subsequences acquired in the above-mentioned starting detection point scenario, and in the embodiment of the present application, the number is at least 2. Afterwards, the clarity of each image in the initial image subsequence is calculated based on the preset image clarity evaluation algorithm, and if the clarity value of each image is within the second preset threshold range, the initial image subsequence is determined to be the target image sequence of the current point to be detected.

[0065] If the clarity value of each image is not within the second preset threshold range, that is, the clarity of at least one image is not within the second preset threshold range, then the initial focus subsequence of the current position is adjusted according to the image clarity calculation result and the minimum focus distance of the microscope lens to generate an adjusted focus subsequence of the current detection point. It can also be understood that, based on the image clarity calculation result, the minimum focus distance of the microscope lens is adjusted up or down on the basis of the current initial focus subsequence to generate a new adjusted focus subsequence. Afterwards, the adjusted image subsequence corresponding to the adjusted focus subsequence of the current position is obtained, and it is re-determined whether the clarity values ​​of each image in the adjusted image subsequence are all within the second preset threshold range. If the clarity values ​​of each image in the adjusted image subsequence are all within the second preset threshold range, the adjusted image subsequence is determined to be the target image sequence of the current position. Taking into account that the initial image subsequence collected by the microscope lens at the current detection point may have partially blurred images, low clarity, and does not meet the second preset threshold range, fine-tuning is performed on the basis of the original initial focal length subsequence to obtain an adjusted focal length subsequence, thereby ensuring the clarity of the acquired image and further improving the quality of the fused image.

[0066] In the present application scheme, a clear image of the back side of the wafer at the current point to be inspected is obtained based on the clear image subsequence obtained at the previous inspection point and the height difference between the current inspection point and the previous inspection point. A target image subsequence of a preset length with higher clarity that has been obtained at the previous inspection point may have a height difference at the current point to be inspected, but the height difference between the positions of the two inspection points is generally very small. Therefore, the target image subsequence of the current inspection point can be obtained by fine-tuning the focal length based on the sequence images obtained at the previous inspection point, thereby saving the time for acquiring the image and the time for calculating the image clarity, thereby improving the efficiency of the image fusion process, and at the same time, a higher-definition image of the back side of the wafer can be obtained to facilitate subsequent defect detection on the back side of the wafer.

[0067] In one embodiment, the step of obtaining the defect detection result of the back side of the wafer to be detected according to the color scale difference of the target clear image of all the points to be detected can be specifically performed as follows:

[0068] Determine whether there is a color scale difference in the target clear images of all the points to be detected; if there is no color scale difference in the target clear images of all the points to be detected, it is determined that there is no defect on the back of the wafer to be detected; otherwise, it is determined that there is a defect on the back of the wafer to be detected. Specifically, the back of a wafer to be detected contains several points to be detected. If there is no color scale difference in the target clear images of each point to be detected, it is considered that there is no defect on the back of the wafer to be detected. If at least one of all the acquired target clear images has a color scale difference, it is determined that there are defects such as dirt, foreign matter, and scratches on the back of the wafer to be detected.

[0069] In the present application, since the structure of the back side of the wafer is simple, it is possible to simply and efficiently determine whether there is a defect on the back side of the wafer based on the color gradation difference. If there is no color gradation difference in the images of all the points to be detected, it is determined that there is no defect. If there is a color gradation difference in at least one image, it is determined that there is a defect, thereby improving the efficiency of defect detection.

[0070] Figure 1 FIG. 1 is a flow chart of a method for detecting defects on the back side of a wafer in one embodiment. It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but the steps are not necessarily executed in the order indicated by the arrows; unless otherwise specified in this document, there is no strict order restriction for the execution of the steps, and the steps may be executed in other orders; and Figure 1At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0071] Based on the above method, an embodiment of the present application also discloses a wafer back side defect detection device.

[0072] Reference Figure 3 , the device includes the following modules:

[0073] The target image acquisition module 301 is used to determine the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and to acquire the target image sequence corresponding to the point to be detected according to the target focal length sequence;

[0074] A clear image generation module 302 is used to perform image fusion processing on each image in the target image sequence to obtain a clear target image of the point to be detected;

[0075] The back defect determination module 303 is used to obtain the target clear images of all the points to be detected on the back of the wafer to be detected, and obtain the defect detection result of the back of the wafer to be detected according to the color scale difference of the target clear images of all the points to be detected.

[0076] In one embodiment, the target image acquisition module 301 is specifically used to be applied to any starting point to be inspected on the back side of the wafer to be inspected, and determine the starting focal length sequence of the microscope lens according to the obtained minimum focusing distance of the microscope lens and the acceptable height difference of the wafer to be inspected; obtain the starting image sequence collected by the microscope lens at the starting point to be inspected, wherein the starting image sequence is adapted to the starting focal length sequence; calculate the clarity of each image in the starting image sequence based on a preset image clarity evaluation algorithm, determine the target focal length sequence according to the preset sequence length, and determine the image subsequence with the highest clarity score as the target image sequence.

[0077] In one embodiment, the target image acquisition module 301 is specifically used to be applied to any non-starting point to be inspected on the back side of the wafer to be inspected, and to determine the target focal length of the current point to be inspected based on the target image sequence of the previous inspection point; to obtain the first image captured by the microscope lens at the current point to be inspected, wherein the first image is adapted to the target focal length; to calculate the clarity of the first image based on a preset image clarity evaluation algorithm, to compare the clarity of the first image with a first preset threshold, and to determine the target image sequence at the current position based on the comparison result.

[0078] In one embodiment, the target image acquisition module 301 is specifically used to set the first image as a target image sequence if the clarity value of the first image is within a first preset threshold range; determine an initial focal length subsequence according to the target focal length if the clarity value of the first image is not within the first preset threshold range; obtain an initial image subsequence collected by the microscope lens at the current point to be detected, wherein the initial image subsequence is adapted to the initial focal length subsequence; calculate the clarity of each image in the initial image subsequence based on a preset image clarity evaluation algorithm, and if the clarity value of each image is within a second preset threshold range, determine that the initial image subsequence is the target image sequence of the current point to be detected.

[0079] In one embodiment, the target image acquisition module 301 is specifically used to calculate the clarity of each image in the target image sequence of the previous detection point according to a preset image clarity evaluation algorithm, and determine the focal length corresponding to the image with the highest clarity; calculate the height difference between the current point to be detected and the previous detection point, and determine the target focal length of the current point to be detected based on the height difference and the focal length corresponding to the image with the highest clarity at the previous detection point.

[0080] In one embodiment, the back defect judgment module 303 is specifically used to determine whether there is a color scale difference in the target clear images of all points to be detected; if there is no color scale difference in the target clear images of all points to be detected, it is determined that there is no defect on the back side of the wafer to be detected; otherwise, it is determined that there is a defect on the back side of the wafer to be detected.

[0081] In one embodiment, the preset sequence length in the target image acquisition module 301 is at least 2.

[0082] The wafer back side defect detection device provided in the embodiment of the present application can be applied to the wafer back side defect detection method provided in the above embodiment. For relevant details, refer to the above method embodiment. The implementation principle and technical effect are similar and will not be repeated here.

[0083] It should be noted that: when the wafer back side defect detection device provided in the embodiment of the present application performs wafer back side defect detection, only the division of the above-mentioned functional modules / functional units is used as an example for illustration. In actual applications, the above-mentioned functions can be assigned to different functional modules / functional units as needed, that is, the internal structure of the wafer back side defect detection device is divided into different functional modules / functional units to complete all or part of the functions described above. In addition, the implementation method of the wafer back side defect detection method provided in the above method embodiment and the implementation method of the wafer back side defect detection device provided in this embodiment belong to the same concept. The specific implementation process of the wafer back side defect detection device provided in this embodiment is detailed in the above method embodiment, which will not be repeated here.

[0084] The embodiment of the present application also discloses a computer device.

[0085] Specifically, if Figure 4 As shown, the computer device can be a computer device such as a desktop computer, a laptop computer, a PDA, and a cloud server. The computer device may include, but is not limited to, a processor and a memory. The processor and the memory may be connected via a bus or otherwise. The processor may be a central processing unit (CPU). The processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, graphics processors (GPU), embedded neural network processors (NPU) or other dedicated deep learning coprocessors, discrete gates or transistor logic devices, discrete hardware components and other chips, or a combination of the above-mentioned various chips.

[0086] As a non-transient computer-readable storage medium, the memory can be used to store non-transient software programs, non-transient computer executable programs and modules, such as program instructions / modules corresponding to the methods in the above-mentioned embodiments of the present application. The processor executes various functional applications and data processing of the processor by running the non-transient software programs, instructions and modules stored in the memory, that is, the method in the above-mentioned method implementation is realized. The memory may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created by the processor, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some embodiments, the memory may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network and a combination thereof.

[0087] The embodiment of the present application also discloses a computer-readable storage medium.

[0088] Specifically, a computer-readable storage medium is used to store a computer program, and when the computer program is executed by a processor, the method in the above-mentioned method implementation is implemented. Those skilled in the art will understand that the implementation of all or part of the process in the above-mentioned implementation method of the present application can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and the program, when executed, may include the process of the implementation of the above-mentioned methods. Among them, the storage medium may be a disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory (Flash Memory), a hard disk (Hard Disk Drive, abbreviated as: HDD) or a solid-state drive (SSD), etc.; the storage medium may also include a combination of the above-mentioned types of memory.

[0089] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for detecting defects on the back side of a wafer, characterized in that: The method is applied to an automatic optical detection system for wafer backside defects, wherein the automatic optical detection system for wafer backside defects comprises a microscope lens, wherein the microscope lens is used to collect an image of the backside of a wafer to be detected, and the focal length of the microscope lens is adjustable. The method comprises: Determine the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquire the target image sequence corresponding to the point to be detected according to the target focal length sequence; Performing image fusion processing on each image in the target image sequence to obtain a clear target image of the point to be detected; Obtain a target clear image of all the points to be detected on the back side of the wafer to be detected, and obtain a defect detection result on the back side of the wafer to be detected based on the color scale difference of the target clear image of all the points to be detected.

2. The method according to claim 1, characterized in that: Determining the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquiring the target image sequence corresponding to the point to be detected according to the target focal length sequence comprises: Applied to any starting point to be inspected on the back side of the wafer to be inspected, the starting focal length sequence of the microscope lens is determined according to the acquired minimum focusing distance of the microscope lens and the acceptable height difference of the wafer to be inspected; Acquire a starting image sequence collected by the microscope lens at the starting point to be detected, wherein the starting image sequence is compatible with the starting focal length sequence; The clarity of each image in the starting image sequence is calculated based on a preset image clarity evaluation algorithm, a target focal length sequence is determined according to a preset sequence length, and an image subsequence with the highest clarity score is determined as a target image sequence.

3. The method according to claim 1, characterized in that: Determining the target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and acquiring the target image sequence corresponding to the point to be detected according to the target focal length sequence comprises: Applied to any non-starting point to be inspected on the back side of the wafer to be inspected, the target focal length of the current point to be inspected is determined according to the target image sequence of the previous point to be inspected; Acquire a first image captured by the microscope lens at the current point to be detected, wherein the first image is adapted to the target focal length; The clarity of the first image is calculated based on a preset image clarity evaluation algorithm, the clarity of the first image is compared with a first preset threshold, and the target image sequence at the current position is determined according to the comparison result.

4. The method according to claim 3, characterized in that: The step of comparing the clarity of the first image with a first preset threshold and determining the target image sequence at the current position according to the comparison result includes: If the clarity value of the first image is within a first preset threshold range, setting the first image as a target image sequence; If the clarity value of the first image is not within a first preset threshold range, determining an initial focal length subsequence according to the target focal length; Acquire an initial image subsequence collected by the microscope lens at the current point to be detected, wherein the initial image subsequence is compatible with the initial focal length subsequence; The clarity of each image in the initial image subsequence is calculated based on a preset image clarity evaluation algorithm. If the clarity value of each image is within a second preset threshold range, the initial image subsequence is determined to be the target image sequence of the current point to be detected.

5. The method according to claim 3, characterized in that: Determining the target focal length of the current point to be detected based on the target image sequence of the previous detection point includes: Calculating the clarity of each image in the target image sequence of the previous detection point according to a preset image clarity evaluation algorithm, and determining the focal length corresponding to the image with the highest clarity; The height difference between the current point to be detected and the last detected point is calculated, and the target focal length of the current point to be detected is determined according to the height difference and the focal length corresponding to the image with the highest definition at the last detected point.

6. The method according to claim 1, characterized in that: The step of obtaining the defect detection result of the back side of the wafer to be detected according to the color scale difference of the target clear image of all the points to be detected includes: Determine whether there is a color scale difference in the target clear image of all points to be detected; If the target clear images of all the points to be inspected do not have color scale differences, it is determined that there is no defect on the back side of the wafer to be inspected; Otherwise, it is determined that there is a defect on the back side of the wafer to be inspected.

7. The method according to claim 2, characterized in that: The preset sequence length is at least 2.

8. A wafer backside defect detection device, characterized in that: The device is applied to an automatic optical detection system for defects on the back side of a wafer. The automatic optical detection system for defects on the back side of a wafer comprises a microscope lens, which is used to collect an image of the back side of a wafer to be detected. The focal length of the microscope lens is adjustable. The device comprises: A target image determination module (301) is used to determine a target focal length sequence of the microscope lens at the point to be detected according to the position of the point to be detected, and to obtain a target image sequence corresponding to the point to be detected according to the target focal length sequence; A clear image generation module (302) is used to perform image fusion processing on each image in the target image sequence to obtain a clear target image of the point to be detected; The back defect determination module (303) is used to obtain the target clear images of all the points to be detected on the back of the wafer to be detected, and obtain the defect detection result of the back of the wafer to be detected according to the color scale difference of the target clear images of all the points to be detected.

9. A computer device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program which can be loaded by the processor and executes the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: A computer program is stored which can be loaded by a processor and execute the method according to any one of claims 1 to 7.

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