Wafer focal plane database acquisition method and device, storage medium and terminal

Abstract

The application discloses a wafer focal plane database acquisition method and device, a storage medium and a terminal, wherein the method comprises the following steps: acquiring wafer image data of a test wafer at multiple image acquisition heights, and calculating image characteristic values of each image module; all image modules corresponding to the same module position of the test wafer in all wafer image data are taken as an image module group of the corresponding module position of the test wafer; based on the image acquisition heights and the image characteristic values corresponding to all image modules in each image module group, the best focal plane height of each image module group at the corresponding module position of the test wafer is acquired; and a wafer focal plane database is formed based on all module positions in the test wafer and the best focal plane height of each module position. When other wafers in the same state are scanned, the application can achieve the purpose of real-time focusing, and has the advantages of high focusing accuracy, short time consumption and the like.

Description

Technical Field

[0001] This invention relates to the field of optical inspection technology, and in particular to a method and apparatus for acquiring a wafer focal plane database, a storage medium, and a terminal. Background Technology

[0002] In automated optical inspection of wafers, automated optical inspection equipment typically uses photodetectors for autofocusing or image sharpness evaluation functions for passive focusing. Among these, image-based passive focusing methods are widely used due to their low cost, low power consumption, and flexible and easy-to-control algorithms.

[0003] Passive focusing methods based on image evaluation typically acquire a series of images near the focal point and analyze each frame to achieve automatic focusing by observing changes in image sharpness. However, this method suffers from a relatively long focusing time. Therefore, existing technologies first establish an offline focal plane database for each point on the surface of the object under test before real-time testing. Currently, the discrete point acquisition method using an area scan camera is commonly used to establish the focal plane database. However, the focusing accuracy of the focal plane database established based on this method is insufficient, resulting in low precision in the acquired wafer scan images. To address this issue, it is necessary to provide a method for constructing a wafer focal plane database that can acquire high-precision wafer scan images. Summary of the Invention

[0004] The purpose of this application is to provide a method, apparatus, storage medium, and terminal for acquiring a wafer focal plane database, which solves the problem that the current offline establishment of focal plane databases for each point on the surface of the object under test is not accurate enough, resulting in low precision of the acquired wafer scanning images.

[0005] In a first aspect, this application provides a method for obtaining a wafer focal plane database, including:

[0006] The wafer image data is acquired when the wafer is located at multiple image acquisition heights. Each wafer image data includes multiple image modules, and the contents of all image modules located at the same position in all wafer image data are corresponding. The image feature value of each image module is calculated.

[0007] All image modules in all the wafer image data that correspond to the same module position of the wafer to be measured are taken as the image module group corresponding to the module position of the wafer to be measured;

[0008] Based on the image acquisition height and image feature value corresponding to all image modules in each group of image modules, the optimal focal plane height of each group of image modules in the measurement wafer is obtained;

[0009] A wafer focal plane database is formed based on the measured positions of all modules in the wafer and the optimal focal plane height for each module position.

[0010] Wherein, the module position in the measured wafer is the position of the module in the measured wafer that corresponds to the image module in the wafer image data.

[0011] In one embodiment of this application, each of the image scan data includes N columns of scan images; dividing each of the wafer image data into multiple image modules using the same partitioning method includes dividing each column of scan images in each of the wafer image data into multiple image modules using the same partitioning method.

[0012] In one embodiment of this application, the image feature value is the image grayscale variance value, and the formula for calculating the image grayscale variance value of the image module is:

[0013] S 2 =[(x1-x) 2 +(x2-x) 2 +……+(xn-x) 2 ] / n

[0014] Where S represents the image grayscale variance of the image module, x1, x2...xn are the image grayscale values ​​of each pixel in the image module, and x is the average value of the image grayscale values ​​of all pixels in the image module.

[0015] In one embodiment of this application, the wafer image data of the measured wafer is acquired by a wafer scanning system, and the measured wafer is placed flat on the wafer carrier platform of the wafer scanning system;

[0016] The process involves acquiring wafer image data at multiple image acquisition heights, where each wafer image data includes multiple image modules. All image modules located at the same position in all wafer image data correspond to each other. Prior to the step of calculating the image feature value of each image module, the process further includes:

[0017] Based on the center position of the measured wafer and the center position of the wafer carrier platform in the wafer scanning system, the center position offset of the measured wafer is obtained, and the center position offset is used as the position offset parameter of each module in the wafer focal plane database.

[0018] The angular offset of the measured wafer is obtained based on the wafer notch direction and the set notch direction.

[0019] The angle offset is sent to the wafer carrier platform control unit of the wafer scanning system, so that the wafer carrier platform control unit controls the wafer carrier platform to perform a position angle offset based on the angle offset, so that the measuring wafer on the wafer carrier platform is located on the wafer carrier platform at a fixed scanning angle.

[0020] In one embodiment of this application, the wafer image data of the measured wafer is acquired by a wafer scanning system, and the measured wafer is placed flat on the wafer carrier platform of the wafer scanning system;

[0021] The method for obtaining the height of the multiple images where the wafer is located is as follows:

[0022] After the scanning camera in the wafer scanning system focuses on any point of the wafer being measured, the height of the wafer being measured is set as the height of the first image acquisition.

[0023] The measuring wafer is measured with the height of the first image acquisition as the starting height. Within a preset vertical height range, the wafer carrier platform is moved upward at a preset step distance. Each step acquires one image acquisition height of the measuring wafer.

[0024] The measurement starts from the height of the first image acquisition and proceeds within a preset vertical height range by stepping the wafer carrier platform downwards at a preset step distance. Each step acquires one image acquisition height of the wafer being measured.

[0025] In one embodiment of this application, the step of obtaining the optimal focal plane height of the corresponding module position in the measured wafer for each group of image modules, based on the image acquisition height and image feature values ​​corresponding to all image modules in each group of image modules, includes:

[0026] Linear fitting is performed on the image acquisition height and image feature value corresponding to all image modules in each group of image modules to obtain the height feature fitting curve of each group of image modules. Based on the height feature fitting curve of each group of image modules, the optimal focal plane height of the corresponding module position in the measurement wafer is obtained.

[0027] In one embodiment of this application, obtaining the optimal focal plane height of the corresponding module position in the measurement wafer based on the height feature fitting curve of the image module group includes:

[0028] The height corresponding to the maximum variance value in the height feature fitting curve of the image module group is taken as the optimal focal plane height of the corresponding module position in the measured wafer.

[0029] In one embodiment of this application, the condition for adjusting the optimal focal height based on the position of each module in the wafer focal plane database is as follows:

[0030] Determine whether the difference between the optimal focal plane height of the target module position in the wafer to be scanned and the current height is greater than half of the depth of field of the scanning camera objective lens in the wafer scanning system. If so, adjust the height of the wafer to be scanned based on the optimal focal plane height of the target module position; otherwise, there is no need to adjust the wafer to be scanned.

[0031] The target module position is any module position in the wafer to be scanned.

[0032] Secondly, this application also provides a wafer focal plane database acquisition device, including an image module acquisition module, an image module group acquisition module, an optimal focal plane height acquisition module, and a wafer focal plane database acquisition module;

[0033] The image module acquisition module is used to acquire wafer image data when the wafer is located at multiple image acquisition heights. Each wafer image data includes multiple image modules, and the content of all image modules located at the same position in all wafer image data corresponds to each other. The module also calculates the image feature value of each image module.

[0034] The image module group acquisition module is used to take all the image modules in all the wafer image data that correspond to the same module position of the wafer to be measured as the image module group corresponding to the module position of the wafer to be measured;

[0035] The optimal focal plane height acquisition module is used to acquire the optimal focal plane height of the corresponding module position in the measured wafer based on the image acquisition height and image feature value of all image modules in each group of image modules.

[0036] The wafer focal plane database acquisition module is used to form a wafer focal plane database based on the measured positions of all modules in the wafer and the optimal focal plane height of each module position.

[0037] Wherein, the module position in the measured wafer is the position of the module in the measured wafer that corresponds to the image module in the wafer image data.

[0038] Thirdly, this application also provides a storage medium storing a computer program thereon, characterized in that the program, when executed by a processor, implements the wafer focal plane database acquisition method.

[0039] Fourthly, this application also provides a terminal, including: a processor and a memory, wherein the memory and the processor are communicatively connected;

[0040] The memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory to enable the terminal to perform the wafer focal plane database acquisition method as described above.

[0041] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0042] The wafer focal plane database acquisition method provided in this invention acquires wafer image data for measuring the acquisition height of multiple images on a wafer. Each wafer image data includes multiple image modules. Then, based on the image acquisition height and image feature values ​​of all image modules at the same location on the wafer, a quadratic linear fitting is performed, and the optimal focal plane height at the corresponding location on the wafer is obtained through the fitted curve. Since the size of the image modules in the wafer image data can be set according to actual needs, a continuously adjustable database or an intermittently adjustable database can be established. This invention is an offline wafer focal plane database establishment method, which can achieve real-time focusing when scanning other wafers under the same conditions, and has advantages such as high focusing accuracy and short time consumption.

[0043] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0044] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0045] Figure 1 The diagram shown is a flowchart illustrating the wafer focal plane database acquisition method described in this application embodiment.

[0046] Figure 2 The diagram shown is a schematic representation of the wafer scanning system in the wafer focal plane database acquisition method described in this application embodiment.

[0047] Figure 3 The image shown is an example of wafer image data in the wafer focal plane database acquisition method described in this application embodiment.

[0048] Figure 4 The diagram shows a continuous focal plane curve for determining the position of a certain column of modules on a wafer in the wafer focal plane database acquisition method described in this application embodiment.

[0049] Figure 5The diagram shows a discontinuous focal plane curve for determining the position of a certain column of modules on a wafer in the wafer focal plane database acquisition method described in this application embodiment.

[0050] Figure 6 The diagram shown is a schematic representation of the wafer focal plane database acquisition device described in an embodiment of this application.

[0051] Figure 7 The diagram shown is a structural schematic of the terminal described in an embodiment of this application. Detailed Implementation

[0052] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0053] The following embodiments of this application provide a method and apparatus for obtaining a wafer focal plane database, a storage medium, and a terminal, which are used to solve the problem that the current offline establishment of focal plane databases for each point on the surface of the object under test is not accurate enough, resulting in low accuracy of the obtained wafer scanning images.

[0054] The following will describe in detail, with reference to the accompanying drawings, the principles and implementation methods of a wafer focal plane database acquisition method, apparatus, storage medium and terminal of this embodiment, so that those skilled in the art can understand the wafer focal plane database acquisition method, apparatus, storage medium and terminal of this embodiment without creative effort.

[0055] like Figure 1 As shown in the figure, this embodiment provides a method for obtaining a wafer focal plane database, which includes the following steps.

[0056] Step S101: Obtain wafer image data when the wafer is located at multiple image acquisition heights. Each wafer image data includes multiple image modules, and the contents of all image modules located at the same position in all wafer image data are corresponding. Calculate the image feature value of each image module.

[0057] The wafer to be scanned to obtain a wafer focal plane database is designated as the measurement wafer. The measurement wafer can be any intact wafer. In this embodiment, wafer image data of the measurement wafer can be acquired through a wafer scanning system, and the acquired wafer focal plane database can also be applied to the scanning process of the wafer to be scanned using the wafer scanning system or a similar system. Furthermore, this embodiment can also acquire wafer image data through other wafer image data acquisition methods.

[0058] refer to Figure 2As shown, the wafer scanning system used in this embodiment includes a control module, an optical imaging module connected to the control module, and a wafer carrier platform. The control module includes a wafer carrier platform control unit for controlling the wafer carrier platform to carry the measurement wafer and perform X / Y / Z degree-of-freedom motion. The optical imaging module includes a scanning camera and other optical components for scanning and imaging the wafer on the wafer carrier platform and acquiring scanning data. The wafer scanning system and its modules also include other reasonable units, which will not be described in detail here. This embodiment can also use wafer scanning systems with other structures capable of performing measurement wafer scanning; this embodiment does not impose any fixed limitations on them.

[0059] Specifically, in this embodiment, the wafer to be measured is first placed on the wafer carrier platform manually or automatically, ensuring the wafer is placed flat on the platform. Then, the wafer carrier platform is moved up and down to position the wafer at multiple image acquisition heights. The wafer scanning system then scans and acquires wafer image data at these multiple image acquisition heights. The method for acquiring the multiple image acquisition heights of the wafer is as follows: the scanning camera in the wafer scanning system focuses on any point on the wafer, and the height at which the wafer is positioned after focusing is defined as the first image acquisition height. Preferably, the height at which the wafer is positioned after the scanning camera in the wafer scanning system focuses on the center position of the wafer can be set as the first image acquisition height. Further, the method for determining the center position of the wafer can be as follows: the upper, lower, left, and right edge points of the wafer carrier platform are moved to appear in the field of view of the scanning camera, and the center position of the wafer can be determined based on the coordinates of these four edge points. It should be noted that other reasonable methods can also be used to determine the center position of the wafer; no fixed limitation is imposed here.

[0060] Then, starting from the first image acquisition height, multiple other image acquisition heights of the wafer are acquired by stepping upwards and downwards on the wafer carrier platform. Further, starting from the first image acquisition height, the wafer carrier platform steps upwards within a preset vertical height range Zm with a preset step size, acquiring one image acquisition height for the wafer with each step; thus, multiple other image acquisition heights above the first image acquisition height are acquired. Simultaneously, starting from the first image acquisition height, the wafer carrier platform also steps downwards within a preset vertical height range Zm with a preset step size, acquiring one image acquisition height for the wafer with each step; thus, multiple other image acquisition heights below the first image acquisition height are acquired. This process yields multiple image acquisition heights for the wafer. For example, Zm can be set to 35µm, and the preset step size can be set to 5µm. Multiple image acquisition heights can also be acquired in other reasonable ways, without fixed limitations here.

[0061] After acquiring multiple image acquisition heights, keeping all scanning conditions unchanged except for the height of the wafer carrier platform, the height of the wafer carrier platform is raised or lowered to ensure that the wafer being measured is located at multiple image acquisition heights. The wafer image data of the wafer being measured at each image acquisition height is then acquired through the wafer scanning system.

[0062] It should be noted that the above wafer image data were all acquired using a specific scanning strategy, for reference only. Figure 3 As shown, the wafer surface is scanned vertically in column form to obtain N columns of scanned images, which together form the wafer image data. Preferably, the vertical scanning can be set to scan from one side to the other, or from the middle to both sides, etc.

[0063] Then, using the same partitioning method, each column of scanned images in each wafer image data is divided into multiple image modules. Since all wafer image data are of the same size, and the same partitioning method is used for each column of scanned images in each wafer image data, the image modules divided from all wafer image data should have a positional correspondence. That is, the content of all image modules located at the same position in all wafer image data should correspond. For example, the image size and content of the image module in the Wth column and Kth image in all wafer image data should be the same; the only difference between the corresponding image modules is the clarity. Image modules are as follows... Figure 3 As shown in the image.

[0064] Preferably, a sliding window method can be used to divide each column of scanned images in the wafer image data. For example, a focusing window w*h is set, where w is the camera's field of view width and h is the window height (h can be set to a certain number of pixels according to the objective lens magnification); the window moves from the starting coordinates of a column of scanned images; each time the window overlaps with the image, image data of the window size is extracted as an image module.

[0065] It should be noted that the type of focal plane curve formed by the optimal image acquisition height corresponding to the position of each column of modules on the wafer will also be different when the window size is set differently (the definition of the module position in the wafer is shown below). For example, under low magnification, when the width of the column scan image is constant, the focal plane curve formed by the optimal image acquisition height corresponding to the position of a certain column of modules when the window height h≈5 is as follows: Figure 4 As shown, this focal plane curve is a continuous focal plane curve; in this curve, the Y-axis represents the position of each module in the column module position, and the Z-axis represents the optimal focal plane height corresponding to each module position in the column module position. The focal plane curve formed by the optimal image acquisition height corresponding to a certain column module position when the window height h≈100 is shown below. Figure 5As shown, the focal plane curve is a discontinuous focal plane curve; in this curve, the Y-axis represents the position of each module in the column module position, and the Z-axis represents the optimal focal plane height corresponding to each module position in the column module position. In this embodiment, the window size can be set according to requirements without imposing too many restrictions on it.

[0066] Then, the image feature value of each image module in all wafer image data is calculated. Preferably, the image feature value is the image grayscale variance value, and the specific calculation method of the image grayscale variance value of the image module is as follows:

[0067] S 2 =[(x1-x) 2 +(x2-x) 2 +……+(xn-x) 2 ] / n

[0068] Where S represents the image grayscale variance of the image module, x1, x2…xn are the image grayscale values ​​of each pixel in the image module, and x is the average value of the image grayscale values ​​of all pixels in the image module.

[0069] It should be noted that image feature values ​​can also be set to other reasonable feature values ​​of the image, such as gray-scale weighted average and gray-scale average, etc., but they are not fixed here.

[0070] Step S102: In all wafer image data, all image modules corresponding to the same module position of the wafer are taken as the image module group for determining the corresponding module position of the wafer.

[0071] Since the wafer image data corresponds to the measurement wafer, all image modules defined based on the wafer image data have a corresponding module position on the measurement wafer. Therefore, the measurement wafer can be divided into multiple modules using the same division method as the wafer image data, and the position of each module on the measurement wafer is the module position. There is a one-to-one correspondence between the modules defined based on the measurement wafer and the image modules defined based on the wafer image data.

[0072] Then, all image modules corresponding to the same module position on the wafer from all wafer image data are grouped into image module groups, and these image module groups are used as the image module groups for determining the corresponding module positions on the wafer. For example, the image module at the k-th position in the w-th column of all wafer image data is grouped into an image data group for determining the position of the k-th module in the w-th column of the wafer. This process is then used to obtain the image data group corresponding to the position of each module on the wafer.

[0073] Step S103: Based on the image acquisition height and image feature value corresponding to all image modules in each image module group, obtain the optimal focal plane height of each image module group at the corresponding module position in the wafer being measured.

[0074] For each image module group, a quadratic linear fit is performed on the image acquisition height and image feature values ​​corresponding to all image modules in the group to obtain the height feature fitting curve for that image module group. Specifically, a quadratic linear curve is fitted with the image acquisition height of all image modules in the group as the x-axis and the image grayscale variance of all image modules in the group as the y-axis. The height corresponding to the maximum variance value in the height feature fitting curve is then obtained, and this height is used as the optimal focal plane height for the corresponding module position of that image module group on the measurement wafer. The optimal focal plane height for all module positions on the measurement wafer can be obtained in this way.

[0075] Step S014: A wafer focal plane database is formed based on the determination of the positions of all modules in the wafer and the optimal focal plane height for each module position.

[0076] A wafer focal plane database is formed by integrating and measuring the positions of all modules in the wafer and the optimal focal plane height corresponding to each module position.

[0077] To facilitate the application of the optimal focal height for each module position in the wafer focal plane database, this embodiment, before scanning the wafer to acquire wafer image data using a wafer scanning system, can also obtain position offset parameters for each module position in the wafer focal plane database based on the position offset between the measured wafer and the center position of the wafer carrier platform. Furthermore, by deflecting the wafer carrier platform, the wafer notch direction of the measured wafer not placed in the set notch direction on the wafer carrier platform can be deflected by an angle to the set notch direction. Further, before setting step S101, the following steps are also included.

[0078] Step S100: Determine the position offset parameters of each module in the wafer focal plane database, determine the angle offset, and deflect the wafer based on the angle offset.

[0079] Specifically, the center position of the wafer is first determined using a scanning camera in the wafer scanning system. Then, the center position of the wafer carrier platform is determined using the scanning camera. Finally, based on the center positions of the wafer and the wafer carrier platform, the offset of the wafer relative to the center position of the carrier platform is determined. This offset is used as the position offset parameter for each module in the wafer focal plane database obtained in subsequent steps. The positions of each module in the wafer focal plane database can be directly offset based on the position offset parameter, so that the center position of the wafer formed by the offset module positions coincides with the center position of the wafer carrier platform. Alternatively, when adjusting the optimal focal plane height of each module position in the wafer focal plane database, the position of the module whose focal length needs to be adjusted is determined based on the position offset parameter, thereby obtaining the corresponding optimal focal plane height.

[0080] Simultaneously, the offset between the wafer notch direction and the set notch direction is determined by the scanning camera, which is used as the angular offset of the wafer. The angular offset is then sent to the wafer carrier platform control unit of the wafer scanning system, so that the wafer carrier platform control unit can control the wafer carrier platform to be centered at a fixed scanning angle based on the angular offset (at this time, it is assumed that the wafer notch direction when the wafer is placed on the wafer carrier platform at a fixed scanning angle is the set notch direction).

[0081] It should be noted that the above positions can be obtained in a standard coordinate system. Specifically, the standard coordinate system can be established with the center position of the wafer carrier platform as the origin, any two mutually perpendicular directions on the horizontal plane where the wafer carrier platform is located as the X-axis and Y-axis, and the vertical direction of the wafer carrier platform as the Z-axis. The standard coordinate system can also be established in other reasonable ways, and this embodiment does not impose any fixed restrictions on it.

[0082] Furthermore, in this embodiment, after obtaining the center position offset and angle offset in step S100, the wafer to be measured is not adjusted by deflection and movement based on the center position offset and angle offset. Instead, the center position offset and angle offset are stored in the wafer focal plane database. During the application of the wafer focal plane database, the wafer to be scanned is adjusted based on the center position offset and angle offset. Alternatively, coordinate system conversion is performed between the center position offset and angle offset stored in the wafer focal plane database and the center position offset and angle offset of the wafer to be scanned. The coordinate system conversion process is existing technology and will not be described in detail here, but this method involves a large amount of computation.

[0083] In the process of adjusting the height of the wafer to be scanned using the wafer focal plane database provided in this embodiment, in order to reduce unnecessary adjustments to the height of the wafer to be scanned, the wafer focal plane database adjustment condition can be set as follows: determine whether the difference between the optimal focal plane height of the target module position in the wafer to be scanned and the current height is greater than half of the depth of field of the objective lens of the scanning camera in the wafer scanning system. If so, the height of the wafer to be scanned is adjusted based on the optimal focal plane height of the target module position, thereby completing the scanning work of the target module position. If the difference between the optimal focal plane height of the target module position in the wafer to be scanned and the current height is not greater than half of the depth of field of the objective lens of the scanning camera in the wafer scanning system, it means that a clearer scanned image can be obtained simply by adjusting the depth of field of the scanning camera objective lens.

[0084] In the above description, the target module position refers to any module position in the wafer to be scanned. This means that the image scanning process for each module position in the wafer to be scanned must be determined by the aforementioned adjustment conditions. It should be noted that the method for obtaining the positions of each module in the wafer to be scanned is the same as that for obtaining the positions of modules in the wafer to be measured. Furthermore, when dividing the wafer to be scanned based on the same division method as the wafer image data, the placement position and wafer notch angle on the wafer carrier platform are identical for both the wafer to be scanned and the wafer to be measured. In other words, before scanning the wafer to be scanned, operations such as deflection and movement of the wafer carrier platform are required to position the wafer to be scanned at a fixed scanning angle at the center of the wafer carrier platform.

[0085] The wafer focal plane database acquisition method provided in this invention acquires wafer image data for measuring the acquisition height of multiple images on a wafer. Each wafer image data includes multiple image modules. Then, based on the image acquisition height and image feature values ​​of all image modules at the same location on the wafer, a quadratic linear fitting is performed, and the optimal focal plane height at the corresponding location on the wafer is obtained through the fitted curve. Since the size of the image modules in the wafer image data can be set according to actual needs, a continuously adjustable database or an intermittently adjustable database can be established. This invention is an offline wafer focal plane database establishment method, which can achieve real-time focusing when scanning other wafers under the same conditions, and has advantages such as high focusing accuracy and short time consumption.

[0086] like Figure 6 As shown, this embodiment provides a wafer focal plane database acquisition device, including an image module acquisition module, an image module group acquisition module, an optimal focal plane height acquisition module, and a wafer focal plane database acquisition module.

[0087] The image acquisition module is used to acquire wafer image data when the wafer is located at multiple image acquisition heights. Each wafer image data includes multiple image modules, and the content of all image modules located at the same position in all wafer image data corresponds to each other. The module also calculates the image feature value of each image module.

[0088] The image module group acquisition module is used to select all image modules in all wafer image data that correspond to the same module position on the wafer as the image module group for determining the corresponding module position on the wafer.

[0089] The optimal focal plane height acquisition module is used to obtain the optimal focal plane height of the corresponding module position in the wafer for each image module group based on the image acquisition height and image feature value of all image modules in each image module group.

[0090] The wafer focal plane database acquisition module is used to form a wafer focal plane database based on the determination of the positions of all modules in the wafer and the optimal focal plane height for each module position.

[0091] Among them, determining the module position in the wafer means determining the position of the module in the wafer that corresponds to the image module in the wafer image data.

[0092] The wafer focal plane database acquisition device provided in this invention acquires wafer image data for measuring the acquisition height of multiple images on a wafer. Each wafer image data includes multiple image modules. Then, based on the image acquisition height and image feature values ​​of all image modules at the same location on the wafer, a quadratic linear fitting is performed, and the optimal focal plane height at the corresponding location on the wafer is obtained through the fitted curve. Since the size of the image modules in the wafer image data can be set according to actual needs, a continuously adjustable database or an intermittently adjustable database can be established. This invention is an offline wafer focal plane database establishment device, which can achieve real-time focusing when scanning other wafers under the same conditions, and has advantages such as high focusing accuracy and short time consumption.

[0093] This application also provides a computer-readable storage medium. Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing a processor. The program can be stored in a computer-readable storage medium, which is a non-transitory medium, such as random access memory, read-only memory, flash memory, hard disk, solid-state drive, magnetic tape, floppy disk, optical disk, and any combination thereof. The storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. This available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., digital video disc (DVD)), or a semiconductor medium (e.g., solid-state drive (SSD)).

[0094] like Figure 7 As shown, this application provides a terminal.

[0095] The terminal in this embodiment includes a processor and a memory connected to each other; the memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory, so that the terminal can implement all or part of the steps in the method of the above embodiment when it is executed.

[0096] The beneficial effects of all or part of the steps of the above embodiments are the same as the beneficial effects obtained by the terminal provided by the embodiments of the present invention, and will not be described again here.

[0097] It should be noted that the memory may include random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device. Similarly, the processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0098] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for obtaining a wafer focal plane database, comprising: The wafer image data is acquired when the wafer is located at multiple image acquisition heights. Each wafer image data includes multiple image modules, and the contents of all image modules located at the same position in all wafer image data are corresponding. The image feature value of each image module is calculated. All image modules in all the wafer image data that correspond to the same module position of the wafer to be measured are taken as the image module group corresponding to the module position of the wafer to be measured; Based on the image acquisition height and image feature value corresponding to all image modules in each group of image modules, the optimal focal plane height of the corresponding module position in the measured wafer for each group of image modules is obtained. A wafer focal plane database is formed based on the measured positions of all modules in the wafer and the optimal focal plane height for each module position. Wherein, the module position in the measured wafer is the position of the module in the measured wafer that corresponds to the image module in the wafer image data.

2. The method according to claim 1, characterized in that, The image feature value is the image grayscale variance value, and the formula for calculating the image grayscale variance value of the image module is: ； Where S represents the image grayscale variance value of the image module, x1, x2...xn are the image grayscale values ​​of each pixel in the image module, x is the average value of the image grayscale values ​​of all pixels in the image module, and n is the total number of pixels in the image module.

3. The method according to claim 1, characterized in that, The wafer image data for measurement is acquired through a wafer scanning system, and the wafer for measurement is placed flat on the wafer carrier platform of the wafer scanning system. The process involves acquiring wafer image data at multiple image acquisition heights, where each wafer image data includes multiple image modules. All image modules located at the same position in all wafer image data correspond to each other. Prior to the step of calculating the image feature value of each image module, the process further includes: Based on the center position of the measured wafer and the center position of the wafer carrier platform in the wafer scanning system, the center position offset of the measured wafer is obtained, and the center position offset is used as the position offset parameter of each module in the wafer focal plane database. The angular offset of the measured wafer is obtained based on the wafer notch direction and the set notch direction. The angle offset is sent to the wafer carrier platform control unit of the wafer scanning system, so that the wafer carrier platform control unit controls the wafer carrier platform to perform a position angle offset based on the angle offset, so that the measuring wafer on the wafer carrier platform is located on the wafer carrier platform at a fixed scanning angle.

4. The method according to claim 1, characterized in that, The wafer image data for measurement is acquired through a wafer scanning system, and the wafer for measurement is placed flat on the wafer carrier platform of the wafer scanning system. The method for obtaining the height of the multiple images where the wafer is located is as follows: After the scanning camera in the wafer scanning system focuses on any point of the wafer to be measured, the height of the wafer to be measured is set as the first image acquisition height. The measurement wafer is measured with the height of the first image acquisition as the starting height. Within a preset vertical height range, the wafer carrier platform is moved upward at a preset step distance. Each step acquires one image acquisition height of the measurement wafer. The measurement starts from the height of the first image acquisition and proceeds within a preset vertical height range by stepping the wafer carrier platform downwards at a preset step distance. Each step acquires one image acquisition height of the wafer being measured.

5. The method according to claim 1, characterized in that, Based on the image acquisition height and image feature values ​​corresponding to all image modules in each group of image modules, the step of obtaining the optimal focal plane height of the corresponding module position in the measured wafer for each group of image modules includes: Linear fitting is performed on the image acquisition height and image feature value corresponding to all image modules in each group of image modules to obtain the height feature fitting curve of each group of image modules. Based on the height feature fitting curve of each group of image modules, the optimal focal plane height of the corresponding module position in the measured wafer is obtained.

6. The method according to claim 5, characterized in that, The optimal focal plane height for the corresponding module position in the measured wafer is obtained based on the height feature fitting curve of the image module group, including: The height corresponding to the maximum variance value in the height feature fitting curve of the image module group is taken as the optimal focal plane height of the corresponding module position in the measured wafer.

7. The method according to claim 1, characterized in that, The conditions for adjusting the optimal focal height of each module position based on the aforementioned wafer focal plane database are as follows: Determine whether the difference between the optimal focal plane height of the target module position in the wafer to be scanned and the current height is greater than half of the depth of field of the scanning camera objective lens in the wafer scanning system. If so, adjust the height of the wafer to be scanned based on the optimal focal plane height of the target module position; otherwise, there is no need to adjust the wafer to be scanned. The target module position is any module position in the wafer to be scanned.

8. A wafer focal plane database acquisition device, characterized in that, It includes an image module acquisition module, an image module group acquisition module, an optimal focal plane height acquisition module, and a wafer focal plane database acquisition module; The image module acquisition module is used to acquire wafer image data when the wafer is located at multiple image acquisition heights. Each wafer image data includes multiple image modules, and the content of all image modules located at the same position in all wafer image data corresponds to each other. The module also calculates the image feature value of each image module. The image module group acquisition module is used to take all the image modules in all the wafer image data that correspond to the same module position of the wafer to be measured as the image module group corresponding to the module position of the wafer to be measured; The optimal focal plane height acquisition module is used to acquire the optimal focal plane height of the corresponding module position in the measured wafer based on the image acquisition height and image feature value of all image modules in each group of image modules. The wafer focal plane database acquisition module is used to form a wafer focal plane database based on the measured positions of all modules in the wafer and the optimal focal plane height of each module position. Wherein, the module position in the measured wafer is the position of the module in the measured wafer that corresponds to the image module in the wafer image data.

9. A storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the wafer focal plane database acquisition method according to any one of claims 1 to 7.

10. A terminal, characterized in that, include: A processor and a memory, wherein the memory and the processor are communicatively connected; The memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to cause the terminal to perform the wafer focal plane database acquisition method as described in any one of claims 1 to 7.

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