Image acquisition method and related device for wafer contour detection

Abstract

The present application provides an image acquisition method and related device for wafer contour detection, which relates to the field of wafer detection technology. The method includes: obtaining multiple initial images that are sequentially acquired while the wafer rotates in one direction, an image acquisition device is used to acquire images of the wafer in the thickness direction of the wafer, a first image to be stitched of the multiple initial images and the remaining images of the multiple initial images other than the first image to be stitched include the same actual area of the wafer; determining a local image within the effective depth of field in each of the other initial images other than the first image to be stitched as a second image to be stitched; and obtaining a target image for wafer contour detection by performing stitching processing based on each second image to be stitched and the first image to be stitched. In this way, the situation in which there is a large error in wafer edge measurement due to the large number of blurred contour parts in the image used for wafer contour detection can be alleviated.

Description

Technical Field

[0001] The present application relates to the field of wafer detection technology, and in particular to an image acquisition method and related devices for wafer contour detection. Background Art

[0002] With the continuous advancement of integrated circuit manufacturing processes, the processing precision of wafers, the carrier of integrated circuits, has continued to increase, making wafer profile measurement increasingly important. Accurate profile measurement ensures wafer surface quality, thereby improving the yield and reliability of the entire manufacturing process. In addition, as process nodes continue to shrink, the lithography process is increasingly sensitive to subtle changes in the wafer profile. Therefore, the use of advanced measurement technology to monitor the wafer edge profile in real time can provide important data support for optimizing production processes and improving product performance.

[0003] Currently, wafer edge measurement mostly relies on machine vision. A camera captures a contour image encompassing the wafer edge. Image processing algorithms then extract the wafer outline to calculate precise edge profile parameters. The wafer is rotated around its center to measure the edge profile at any angle. However, due to various factors, portions of the camera-generated contour image may exceed the camera's effective depth of field, resulting in blurred contours and significant errors in wafer edge measurement. Summary of the Invention

[0004] An embodiment of the present application provides an image acquisition method and related device for wafer contour detection, which stitches local images of the wafer within the depth of field range of multiple images into the same image, so that the obtained image includes more clear wafer contours, thereby alleviating the situation where there are large errors in wafer edge measurement due to the large number of blurred contour parts in the image used for wafer contour detection.

[0005] The embodiments of the present application can be implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides an image acquisition method for wafer contour detection, the method comprising:

[0007] obtaining a plurality of initial images sequentially captured while the wafer rotates in one direction, wherein an image capture device is used to capture images of the wafer in a thickness direction of the wafer, and a first image to be stitched of the plurality of initial images and remaining images of the plurality of initial images other than the first image to be stitched include a same actual area of the wafer;

[0008] determining a partial image located within the effective depth of field in each of the multiple initial images except the first image to be stitched as a second image to be stitched;

[0009] A target image for wafer contour detection is obtained by performing stitching processing based on the second images to be stitched and the first images to be stitched.

[0010] In a second aspect, an embodiment of the present application provides an image acquisition device for wafer contour detection, the device comprising:

[0011] an image acquisition module, configured to acquire a plurality of initial images sequentially acquired while the wafer rotates in one direction, wherein an image acquisition device is configured to acquire images of the wafer in a thickness direction of the wafer, and a first image to be stitched of the plurality of initial images and the remaining images of the plurality of initial images other than the first image to be stitched include a same actual area of the wafer;

[0012] a determining module, configured to determine a partial image located within an effective depth of field in each of the multiple initial images except the first image to be stitched as a second image to be stitched;

[0013] The processing module is configured to obtain a target image for wafer contour detection by performing stitching processing based on the second images to be stitched and the first images to be stitched.

[0014] In a third aspect, an embodiment of the present application provides an electronic device comprising a processor and a memory, wherein the memory stores machine-executable instructions that can be executed by the processor, and the processor can execute the machine-executable instructions to implement the image acquisition method for wafer contour detection described in the aforementioned embodiment.

[0015] In a fourth aspect, an embodiment of the present application provides a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the image acquisition method for wafer contour detection as described in the aforementioned embodiment.

[0016] The image acquisition method and related device for wafer contour detection provided by the embodiment of the present application obtain multiple initial images that are sequentially captured while the wafer is rotating in one direction, and determine the local images of each of the multiple initial images other than the first image to be stitched that are located within the effective depth of field as the second image to be stitched, and then obtain the target image for wafer contour detection by performing stitching processing based on each second image to be stitched and the first image to be stitched. Among them, the image acquisition device is used to capture images of the wafer in the thickness direction of the wafer, and the first image to be stitched of the multiple initial images and the remaining images of the multiple initial images other than the first image to be stitched include the same actual area of the wafer. In this way, the target image includes the clear outline of the wafer in the multiple captured initial images through stitching, thereby alleviating the situation where there is a large error in the wafer edge measurement due to the large number of blurred outline parts in the image used for wafer contour detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 Schematic diagram of a wafer image with edge blurring problem captured by a wafer image acquisition system;

[0019] Figure 2 A block diagram of an electronic device provided in an embodiment of the present application;

[0020] Figure 3 One of the flow charts of the image acquisition method for wafer contour detection provided in an embodiment of the present application;

[0021] Figure 4 One of the two top views of the wafer at the time instants provided in the embodiment of the present application;

[0022] Figure 5 The second top view of the wafer at two moments provided in the embodiment of the present application;

[0023] Figure 6 The second flowchart of the image acquisition method for wafer contour detection provided in an embodiment of the present application;

[0024] Figure 7 Schematic diagram of a top view of a wafer;

[0025] Figure 8Schematic diagram of a wafer image acquisition system provided in an embodiment of the present application;

[0026] Figure 9 It is a sampling timing diagram;

[0027] Figure 10 The third flowchart of the image acquisition method for wafer contour detection provided in an embodiment of the present application;

[0028] Figure 11 A schematic diagram of the position of a wafer in the image field provided in an embodiment of the present application;

[0029] Figure 12 Schematic diagram of the fourth flow chart of the image acquisition method for wafer contour detection provided in an embodiment of the present application;

[0030] Figure 13 One of the block diagrams of the image acquisition device for wafer contour detection provided in an embodiment of the present application;

[0031] Figure 14 This is a second block diagram of an image acquisition device for wafer contour detection provided in an embodiment of the present application.

[0032] Icons: 9-circular grating; 100-electronic device; 110-memory; 120-processor; 130-communication unit; 200-image acquisition device for wafer contour detection; 201-setting module; 202-analysis module; 210-image acquisition module; 220-determination module; 230-processing module. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present application.

[0035] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0036] Currently, wafer edge measurement mostly uses machine vision-based methods. The telecentric optical system and parallel coaxial light source in the system used to collect wafer images constitute the basic structure of wafer measurement. By placing the wafer edge in the effective measurement depth of field of the telecentric optics, the camera can capture a contour image of the wafer edge. Then, based on the image processing algorithm, the wafer contour is extracted to calculate the precise edge contour parameters. The edge contour parameters may include: the front top of the edge, the front top angle, the front top length, the back top, the back top angle, the back top length, etc. The wafer rotates around its center to measure the edge contour morphology at any angle of the wafer. In the above system, an encoder is used to obtain the angle of the wafer.

[0037] Typically, the effective depth of field of telecentric optics is relatively small (usually less than 1mm). Small wafers (typically wafers under 8 inches) have a small radius, so the majority of the arcuate area scanned by the edge measurement system (i.e., the wafer image acquisition system mentioned above) falls within the effective depth of field, allowing for relatively accurate measurements. However, with the continuous advancement of camera technology and the increase in camera target size, the effective depth of field, according to telecentric optics theory, will become even smaller (generally less than 200 microns).

[0038] As wafer sizes continue to increase, traditional vision-based wafer edge measurement faces new technical challenges. Limited by spatial location, the radius of wafers 12 inches and above is too large, and the bow width far exceeds the depth of field of the telecentric lens. The image captured by the camera can clearly feel the edge blur problem, such as Figure 1 The red part shown is the one with blurred edges.

[0039] Combining the above two reasons (i.e., smaller depth of field and larger wafer size), the measurement method based on telecentric optics cannot effectively measure large-sized wafers. The part of the outline close to the center of the circle is far away from the effective depth of field of the telecentric lens. That is, in the camera's field of view, the part close to the center of the wafer is not imaged within the effective depth of field of the telecentric lens. This causes large errors in wafer edge measurement.

[0040] To alleviate the above situation, an embodiment of the present application provides an image acquisition method and related devices for wafer contour detection. By stitching, the target image includes the clear edge contours of the wafer in multiple captured initial images, thereby alleviating the situation where there are large errors in wafer edge measurement due to the large number of blurred contour parts in the image used for wafer contour detection.

[0041] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0042] Please refer to Figure 2 , Figure 2 This is a block diagram of an electronic device 100 provided in an embodiment of the present application. The electronic device 100 may be, but is not limited to, a computer, a server, or the like. The electronic device 100 may include a memory 110, a processor 120, and a communication unit 130. The memory 110, the processor 120, and the communication unit 130 are electrically connected to each other, directly or indirectly, to enable data transmission or interaction. For example, these components may be electrically connected to each other via one or more communication buses or signal lines.

[0043] The memory 110 is used to store programs or data. The memory 110 may be, but is not limited to, random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.

[0044] The processor 120 is used to read / write data or programs stored in the memory 110 and execute corresponding functions. For example, the memory 110 stores an image acquisition device 200 for wafer contour detection. The image acquisition device 200 for wafer contour detection includes at least one software function module stored in the memory 110 in the form of software or firmware. By running the software programs and modules stored in the memory 110, such as the image acquisition device 200 for wafer contour detection in the embodiment of the present application, the processor 120 executes various functional applications and data processing, thereby implementing the image acquisition method for wafer contour detection in the embodiment of the present application.

[0045] The communication unit 130 is used to establish a communication connection between the electronic device 100 and other communication terminals through a network, and to send and receive data through the network.

[0046] It should be understood that Figure 2 The structure shown is only a schematic diagram of the structure of the electronic device 100. The electronic device 100 may also include Figure 2 More or fewer components than shown, or with Figure 2 Different configurations shown. Figure 2 Each component shown in the figure can be implemented by hardware, software or a combination thereof.

[0047] Please refer to Figure 3 , Figure 3 This is a schematic diagram of a flow chart of an image acquisition method for wafer contour detection provided in an embodiment of the present application. The method can be applied to the aforementioned electronic device. The specific flow chart of the image acquisition method for wafer contour detection is described in detail below. In this embodiment, the method may include steps S210 to S230.

[0048] Step S210 , obtaining a plurality of initial images sequentially captured while the wafer is rotating in one direction.

[0049] Step S220: Determine a partial image located within the effective depth of field in each of the multiple initial images except the first image to be stitched as a second image to be stitched.

[0050] Step S230 , performing stitching processing based on the second images to be stitched and the first images to be stitched, to obtain a target image for wafer contour detection.

[0051] In this embodiment, while the wafer rotates in one direction, an image capture device, whose position remains unchanged, is used to capture images of the wafer, thereby obtaining the multiple initial images. The multiple initial images are obtained by capturing images of the wafer along the thickness direction of the wafer using the image capture device. One of the multiple initial images serves as the first image to be stitched together. This first image to be stitched together and the remaining images of the multiple initial images (which may include one or more initial images) other than the first image to be stitched together include the same actual area of the wafer. That is, a portion of the wafer's physical body appears in both the first image to be stitched together and the remaining images of the multiple initial images other than the first image to be stitched together. Each of the multiple initial images other than the first image to be stitched together is treated as an additional initial image. Optionally, the first stitched image and each of the other initial images are grouped as a set of images. Some of the image groups may contain the same actual wafer area, while the remaining image groups may not contain the same actual wafer area. Alternatively, each image group may contain the same actual wafer area, which can be determined by the method of acquiring multiple initial images. For each image group containing the same actual wafer area, the same actual wafer area in each image group may be different. The first image to be stitched serves as a reference image for subsequent stitching, i.e., the other images are stitched toward the first image to be stitched.

[0052] Alternatively, when it is necessary to obtain a target image for wafer contour detection in real time, image acquisition can be performed in real time to obtain the aforementioned multiple initial images. Alternatively, when it is not necessary to obtain a target image for wafer contour detection in real time, image acquisition and storage can be performed first, and then the aforementioned multiple initial images can be determined from the stored images.

[0053] For each of the other initial images, a partial image within the effective depth of field of the other initial image can be analyzed and determined as a second image to be stitched by any method. For example, by analyzing the contours in the image, or by other methods, the second image to be stitched in the other initial image can be determined.

[0054] Subsequently, stitching processing can be performed based on each of the second images to be stitched together and the first image to be stitched together, so that any unclear edge contours in the first images to be stitched together are corrected based on the edge contours indicated by the corresponding second images to be stitched together, thereby obtaining a target image for wafer outline detection. This allows for the stitching of clearly visible edge contours, resulting in a target image that includes a greater number of clear wafer contours, thereby alleviating the problem of large errors in wafer edge measurement caused by a large number of blurred contours in the image used for wafer outline detection.

[0055] Based on the spatial relationship between the wafer and the telecentric system and the motion characteristics of the wafer rotating around its center, Figure 4 It can be seen that at a certain moment t, the camera (i.e. Figure 4 The image acquisition device in the image acquisition device) can obtain a clear outline of point B, but the obtained outline of point A is relatively blurred, and the outline below point A is particularly blurred. Due to the position occlusion, the outline of point C cannot be obtained; in the counterclockwise rotation mode, the wafer rotates to time t+1, and the camera can obtain a clear outline of point E, but the obtained outline of point D is relatively blurred. Due to the position occlusion, the outline of point F cannot be obtained. Point C at time t is between points E and F at time t+1, point B at time t is between points D and E at time t+1, and point A at time t is between point D at time t+1. It can be seen that the original point A jumps out of the telecentric optical field of view. At time t+1, the camera obtains a clear outline of point E, but cannot obtain a clear outline of point A. Among them, Figure 4 The light source is used to provide brightness for image acquisition; Figure 4 The effective depth of field in is the effective depth of field of the image acquisition device.

[0056] Through the above processing of this solution, by stitching the partial images of the wafer within the depth of field of multiple images into the same image, the outline of point A at time t can be used instead of the outline of point A at time t+1, and a complete and clear wafer edge outline can be obtained. By repeating this process, the effective edge of the wafer can be obtained, which can improve the accuracy of wafer edge measurement. It can be understood that Figure 4 This is merely an exemplary description, and the position of the clear contour point in the image at the previous moment in the image at the next moment can be determined based on actual conditions.

[0057] For example, Figure 5 As shown in the figure, when the wafer rotates counterclockwise to time t+1, point C is at the original point B position, and point B is at the original point A position. Point A has already jumped out of the telecentric optical field of view. At this time, the camera captures the effective outline of the original point C, but not the effective outline of the original point B. Similarly, at time t+1, the outline of point B at time t can be used to replace the current outline of point B, thus obtaining a complete and clear wafer edge outline.

[0058] In this embodiment, a sampling rule can be set before image acquisition. This sampling rule indicates how image acquisition is performed. For example, the sampling rule may include a sampling frequency, and subsequent image acquisition can be performed according to this sampling frequency to obtain multiple initial images. The specific value of the sampling frequency can be determined based on actual needs.

[0059] Please refer to Figure 6 , Figure 6 This is a second flow chart of an image acquisition method for wafer contour detection provided in an embodiment of the present application. In this embodiment, Figure 3On the basis shown, before step S210, the method may further include steps S111 to S113, and the sampling rule may be determined through steps S111 to S113.

[0060] Step S111 : calculating a second target angle corresponding to the effective depth of field according to half of the effective depth of field of the image acquisition device and the radius of the wafer.

[0061] Step S112: Calculate a target arc length according to the second target angle and the radius of the wafer.

[0062] Step S113: setting a sampling rule according to the target arc length and / or the resolution of the image acquisition device.

[0063] In this embodiment, the aforementioned Figure 4 and Figure 5 It can be seen that half of the wafer within the effective depth of field of the image acquisition device will be blocked. In this case, the second target angle corresponding to the effective depth of field can be calculated based on half of the effective depth of field of the image acquisition device and the radius of the wafer. The second target angle is the angle corresponding to the sector located within half of the effective depth of field. Afterwards, the arc length of the sector in the wafer with the second target angle as the sector angle can be calculated based on the second target angle and the radius of the wafer as the target arc length. Then, a sampling rule can be set based on the target arc length and / or the resolution of the image acquisition device. The sampling rule may include a sampling frequency.

[0064] Optionally, when setting the sampling rule with a target arc length in mind, when capturing images to obtain an initial image based on the sampling rule, the arc length corresponding to the wafer's rotation angle between two consecutive image captures is less than the target arc length. This prevents the situation where, after stitching, successive contours in the target image appear sequentially as clear, unclear, and then clear, thereby ensuring a good stitching effect.

[0065] Please refer to Figure 7 , Figure 7 is a schematic diagram of a wafer viewed from above. Assuming the effective depth of field of the lens is 2m, half of the effective depth of field is m; and assuming the radius of the wafer is r, the second target angle is: The target arc length corresponding to half the effective depth of field is: When the sampling rule is set based on the target arc length, the arc length corresponding to the angle of rotation of the wafer between two adjacent image acquisitions is less than the target arc length. .

[0066] like Figure 4As shown in the figure, assuming that the initial images obtained from two adjacent image acquisitions are the image obtained at time t and the image obtained at time t+1, respectively. If the sampling rule is set based on the target arc length, that is, the arc length corresponding to the angle of rotation of the wafer between the two adjacent image acquisitions at time t and time t+1 is less than the target arc length, then in the image obtained at time t+1, arcs AB and DE have at least one overlapping point. Therefore, after stitching using the image obtained at time t+1 as the stitching base image, there is no blurred contour edge in arc AE.

[0067] For an object, when it is close to the image acquisition device, the actual size corresponding to one pixel is A; when it is far from the image acquisition device, the actual size corresponding to one pixel is B, where A>B. Since stitching requires stitching images obtained at different times, in order to avoid a large difference in the actual sizes corresponding to the pixels corresponding to the contour edges after stitching, the sampling rule can be set in combination with the resolution of the image acquisition device so that the actual sizes corresponding to the pixels of the second image to be stitched in the initial image obtained by two adjacent image acquisitions differ within a certain range. Optionally, when the sampling rule is set according to the resolution of the image acquisition device, when the initial image is acquired using the sampling rule, the difference in the actual sizes represented by the pixels of the edge contour of the wafer located within the effective depth of field in the images obtained by two adjacent image acquisitions is less than a preset difference.

[0068] Optionally, when the sampling rule indicates a sampling frequency, image acquisition can be performed in combination with the rotation of the wafer. Figure 8 As shown, a circular grating 9 can be added to the wafer mounting area of a conventional wafer image acquisition system to accurately determine the wafer's angular position at time t. The circular grating's signals are used simultaneously for closed-loop control of the servo system and image stitching (i.e., the image acquisition portion). Specifically, the circular grating's TTL signals (i.e., A+ / A-, B+ / B-) are split into two paths: one connected to the servo motor that drives wafer rotation for closed-loop control, and the other connected to the external trigger signal of the image acquisition device, driving the image acquisition device to sample and obtain the initial image.

[0069] In this embodiment, during the wafer rotation process, it is possible to determine whether the wafer's rotation direction is the target direction. If the wafer's rotation direction is determined to be the target direction, image acquisition is performed according to the sampling rule to obtain the multiple initial images. This avoids the situation where sampling is performed while the rotor driving the wafer is retracting, resulting in poor stitching results. Optionally, the wafer's rotation direction can be determined based on the phase relationship between A+ / A- and B+ / B-.

[0070] During image acquisition, sampling can be controlled based on the circular grating's pulse signal. During the first or final image acquisition, counting can be performed based on the circular grating's pulse signal, starting from 0. The sampling time can be determined based on the count result and the target count result indicated by the sampling rule. The target count result is greater than 1. When the sampling time is determined to have arrived, image acquisition is performed to obtain an initial image. This avoids the high processing overhead associated with frequent image acquisition. After receiving the circular grating signal, the image acquisition device can sample according to the sampling sequence using a frequency division algorithm.

[0071] Assuming the wafer rotation speed is ω, the wafer rotates one circle, and the circular grating triggering times is T, then the angle φ rotated by the wafer for each pulse is 2π / T, and the arc length rotated in the circumferential direction is: ; Assuming the target count result is N, then based on the target arc length When setting the target count result N, based on this condition Set the target count result N.

[0072] In this embodiment, the wafer is rotated in such a way that the portion of the wafer within the acquisition range of the image acquisition device rotates toward the image acquisition device, so that subsequent stitching can be performed. In other words, the wafer rotation direction must satisfy the requirement that when looking down at the wafer surface, the linear velocity direction of the portion in the center optical system points toward the camera. If it is away from the camera, dynamic stitching cannot be performed. Figure 5 As shown, the image capture device is at the bottom, the left side of the wafer is within the capture range of the image capture device, and the wafer must be rotated counterclockwise. Under this rotation method, the most recently captured initial image among the multiple initial images is used as the first image to be stitched, and the remaining initial images are used as other initial images. For each other initial image, a second image to be stitched is determined from the other initial images.

[0073] Optionally, the image acquisition device can determine the rotation direction of the wafer through the phase relationship of A+ / A-, B+ / B-, and implement binary incremental trigger sampling, thereby effectively avoiding errors caused by wafer position jitter.

[0074] The following combination Figure 9 , an example is given to illustrate how to collect images.

[0075] When the circular grating rotates, it will send out A, B, and Z three-phase pulse signals. Figure 9 Phases A and B indicated by a and b in the diagram are used to determine the direction of rotation. Figure 9 A / B in a is Figure 9 The two rows A and B in b. Figure 9As shown in Figure 2, during clockwise rotation, signal A leads signal B by 1 / 4 cycle; during counterclockwise rotation, signal B leads signal A by 1 / 4 cycle. Each pulse of the A and B signals corresponds to a fixed mechanical angle increment, such as 0.001°. By counting the number of pulses, the total displacement, or rotation angle, can be calculated. The Z signal is an index signal, generating a pulse once per rotation. It marks the origin and is used to eliminate or calibrate accumulated errors.

[0076] like Figure 9 As shown in b, through the pulse rules of the two signals A and B, we can Figure 9 The b in is divided into two parts.

[0077] The front part (i.e. Figure 9 The left part of the red line in b) signal A leads signal B, indicating that the wafer is rotating clockwise; the rear part (i.e. Figure 9 If the B signal leads the A signal (the right part of the red line in b), it means that the wafer is rotating counterclockwise.

[0078] This solution requires that data be collected while the wafer rotates in the same direction to ensure that the collected wafer position and the data strictly correspond one-to-one. Therefore, when the front part of the wafer rotates clockwise, the count increases every time a pulse is generated by the A and B signals. When the back part rotates counterclockwise, it indicates that the wafer has rotated. If the count is continued at this time, the position collection will be repeated, which cannot correspond to the actual situation. Therefore, the count needs to be reduced.

[0079] Figure 9 The "count" in b is the same as Figure 9 The N in a corresponds to the number N, which controls the sampling density. That is, after N pulses are generated by the A and B signals, a data sample is taken (i.e., an image is acquired). The smaller the value of N, the denser the sampling, while the larger the value, the sparser the sampling. In theory, the smaller the value of N, the better. However, there are several constraints, such as: 1. If N is too small, the sampling will be denser, resulting in excessive measurement data and slow data processing, affecting the measurement cycle. 2. The single sampling time of the sensor is generally constant. If N is set to the minimum value of 1, the grating pulse period must be no less than the single sampling time, requiring the grating to rotate more slowly, affecting the measurement cycle. 3. If N is too small, the grating's own errors will be transmitted to the measurement results. As N increases, the N pulses will accumulate and eliminate some of the errors. When N is set to the maximum value (the pulse value required for one grating rotation), the grating rotation period error disappears.

[0080] Considering the above constraints, and balancing the measurement accuracy and measurement cycle, the following settings can be made: , where T1 is the sampling time and T0 is the pulse period of the circular grating A and B phases.

[0081] In addition, considering that the data needs to be saved, processed, and analyzed in a timely manner after it is obtained, in order to ensure the accuracy of the data, the data analysis and processing must be completed before the next sampling is completed to avoid new data being stored before the previous data is completed. This is also one of the factors affecting N. The following settings can be made: , that is, the minimum value of the aforementioned target counting result is .

[0082] Please refer to Figure 10 , Figure 10 This is a flow chart of the third method for obtaining an image for wafer contour detection provided in the embodiment of the present application. Figure 3 Based on the above, the method may further include steps S121 and S122. As a possible implementation, steps S121 and S122 may be performed before determining the second image to be stitched from one of the other initial images for the first time, that is, before step S220, so as to quickly determine the second image to be stitched from each of the other initial images.

[0083] Step S121 , in a top-down view, according to the effective depth of field of the image acquisition device and the radius of the wafer, calculate a first target angle corresponding to the effective depth of field, and calculate a first bow height corresponding to the effective depth of field according to the target angle and the radius.

[0084] Step S122 , calculating an effective depth of field area corresponding to the wafer image according to the coordinates of the midpoint of the wafer edge in the wafer image captured by the image capture device and the first bow height.

[0085] The first target angle corresponding to the effective depth of field can be calculated based on the effective depth of field of the image acquisition device and the radius of the wafer at a top-down angle. Figure 7 As shown, the position in the camera field of view is as follows Figure 11 As shown. Figure 7 As shown, the first target angle can be an angle calculated based on half of the effective depth of field 2m and the wafer radius r: .

[0086] Assume that the camera field of view of the image acquisition device (i.e., the image field of view) is W*H, and the position of the wafer in this field of view is as follows: Figure 11 As shown, the coordinates of the midpoint of the wafer edge in the image field are (a, b). Then the first bow height is: , and then the first effective depth of field area in the image field can be calculated as That is, in the image field of view Images within the range are within the effective depth of field and do not need to be replaced by stitching, while the rest of the range requires dynamic stitching.

[0087] After determining the first effective depth of field area in the image-side field of view, the partial images corresponding to the first effective depth of field area in each of the other initial images can be used as the second images to be stitched. Optionally, after determining the first effective depth of field area, the first effective depth of field area in the image-side field of view can be directly converted to the image coordinate system used by the acquired wafer image to obtain a second effective depth of field area. Thereafter, the images in each of the other initial images that fall within the second effective depth of field area can be directly used as the second images to be stitched. In this way, by determining the first effective depth of field area in advance, the second images to be stitched in each of the initial images can be quickly determined based on the first effective depth of field area.

[0088] Optionally, in this embodiment, before stitching, the area to be stitched in the first image to be stitched can be determined, and then stitching can be performed in the area to be stitched. Figure 12 , Figure 12 This is a fourth flow chart of an image acquisition method for wafer contour detection provided in an embodiment of the present application. In this embodiment, Figure 3 On the basis shown, before stitching, that is, before step S230, the method may further include steps S131 and S132, and then the to-be-stitched area in the first to-be-stitched image may be directly determined each time stitching is performed.

[0089] In step S131, based on the radius of the wafer and the length of the wafer in the image field of view of the image acquisition device, half the distance between the two end points of the arc of the bow area of the wafer between the image acquisition device and the light source at a top-down angle is calculated as the target bow length.

[0090] Step S132: determining the area to be spliced in the wafer image captured by the image capture device according to the target bow length.

[0091] In this embodiment, if Figure 11 As shown, assuming that the image field of view of the image acquisition device is W*H, and the coordinates of the midpoint of the wafer edge in the image field of view of the image acquisition device are (a, b), the length of the wafer appearing in the image field of view is: Then, the target bow length is Figure 7 As shown, , . When the wafer rotates counterclockwise, the sector PQO can be used as the initial area to be spliced according to the target bow length, wherein P is the midpoint of the wafer edge, O represents the center of the wafer, and the distance between Q and the straight line OP is the target bow length s. The above-mentioned initial area to be spliced can be converted to the coordinate system used by the wafer image captured by the image acquisition device, thereby obtaining the area to be spliced in the wafer image. Afterwards, when an initial image is used as the first image to be spliced, each second image to be spliced can be spliced with the first image to be spliced in the area to be spliced of the first image to be spliced to obtain the target image.

[0092] Optionally, for each second image to be stitched together, the second image to be stitched together and the first image to be stitched together may be registered, or another initial image containing the second image to be stitched together and the first image to be stitched together may be registered to obtain a transformation matrix corresponding to the second image to be stitched together. Subsequently, each second image to be stitched together may be transformed into the coordinate system of the first image to be stitched together based on the transformation matrix corresponding to the second image to be stitched together, and the corresponding blurred partial wafer image in the first image to be stitched together may be replaced with the transformed second image to be stitched together.

[0093] When the to-be-stitched region in the first to-be-stitched image is determined, the blurred local wafer image corresponding to the to-be-stitched region in the first to-be-stitched image is replaced with the converted second to-be-stitched image.

[0094] The above-mentioned image acquisition method for wafer contour detection provided in this embodiment is a dynamic stitching method of edge pixels in wafer contour visual measurement, which can stitch out clearly visible edge contours in the target image, reduce the blurred contours in the image used for wafer contour detection, and thus greatly improve the measurement accuracy of the wafer contour edge.

[0095] In order to execute the corresponding steps in the above embodiments and various possible methods, an implementation method of an image acquisition device 200 for wafer contour detection is given below. Optionally, the image acquisition device 200 for wafer contour detection can adopt the above Figure 2 The device structure of the electronic device shown in FIG. Further, please refer to Figure 13 , Figure 13This is a block diagram of an image acquisition device 200 for wafer contour detection provided in an embodiment of the present application. It should be noted that the basic principles and technical effects of the image acquisition device 200 for wafer contour detection provided in this embodiment are the same as those of the above-mentioned embodiments. For the sake of brevity, any parts not mentioned in this embodiment can be referred to the corresponding contents of the above-mentioned embodiments. The image acquisition device 200 for wafer contour detection may include: an image acquisition module 210, a determination module 220, and a processing module 230.

[0096] The image acquisition module 210 is configured to acquire a plurality of initial images sequentially captured while the wafer rotates in one direction. The image acquisition device is configured to capture images of the wafer in the thickness direction of the wafer, and a first image to be stitched of the plurality of initial images and the remaining images other than the first image to be stitched of the plurality of initial images include the same actual area of the wafer.

[0097] The determining module 220 is configured to determine a partial image located within the effective depth of field in each of the multiple initial images except the first image to be stitched as a second image to be stitched.

[0098] The processing module 230 is configured to perform stitching processing based on the second images to be stitched and the first image to be stitched, so as to obtain a target image for wafer contour detection.

[0099] Please refer to Figure 14 , Figure 14 This is a second block diagram of an image acquisition device 200 for wafer contour detection provided in an embodiment of the present application. In this embodiment, Figure 13 Based on the image acquisition device 200 for wafer contour detection shown, the image acquisition device 200 for wafer contour detection may further include a setting module 201 and an analysis module 202 .

[0100] The setting module 201 is used to: calculate a second target angle corresponding to the effective depth of field based on half of the effective depth of field of the image acquisition device and the radius of the wafer; calculate a target arc length based on the second target angle and the radius of the wafer; set a sampling rule based on the target arc length and / or the resolution of the image acquisition device; wherein, when the sampling rule is set according to the target arc length, when the initial image is acquired using the sampling rule, the arc length corresponding to the angle at which the wafer rotates between two adjacent image acquisitions is less than the target arc length; wherein, when the sampling rule is set according to the resolution of the image acquisition device, when the initial image is acquired using the sampling rule, the difference in actual sizes represented by pixel points of the edge contour of the wafer located within the effective depth of field in the images obtained in two adjacent image acquisitions is less than a preset difference; the multiple initial images are acquired by image acquisition based on the sampling rule.

[0101] The analysis module 202 is used to: calculate a first target angle corresponding to the effective depth of field according to the effective depth of field of the image acquisition device and the radius of the wafer at a top-down angle, and calculate a first bow height corresponding to the effective depth of field according to the target angle and the radius; calculate a first effective depth of field area within the image side field of view according to the coordinates of the midpoint of the wafer edge in the image side field of view of the image acquisition device and the first bow height.

[0102] The determining module 220 is specifically configured to use a partial image corresponding to the first effective depth of field area in each of the other initial images as the partial second image to be stitched.

[0103] Optionally, in this embodiment, the analysis module 202 can also be used to: calculate, based on the radius of the wafer and the length of the wafer in the image field of view of the image acquisition device, half the distance between the end points of the arc of the bow area of the wafer between the image acquisition device and the light source at a top-down angle as the target bow length; and determine, based on the target bow length, the area to be spliced in the wafer image captured by the image acquisition device.

[0104] The processing module 230 is specifically configured to: perform stitching processing on each second image to be stitched and the first image to be stitched in the stitching area of the first image to be stitched, to obtain the target image.

[0105] Optionally, the above modules can be stored in the form of software or firmware. Figure 2 The memory 110 shown in FIG. 110 or the operating system (OS) of the electronic device 100 may be fixed and may be used by Figure 2Meanwhile, the data, program codes, etc. required to execute the above modules may be stored in the memory 110.

[0106] An embodiment of the present application also provides a readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the image acquisition method for wafer contour detection is implemented.

[0107] In summary, the embodiments of the present application provide an image acquisition method and related apparatus for wafer contour detection, which obtains a plurality of initial images sequentially captured while the wafer rotates in one direction, and determines a local image located within the effective depth of field in each of the multiple initial images except the first image to be stitched as the second image to be stitched, and then obtains a target image for wafer contour detection by performing stitching processing based on each second image to be stitched and the first image to be stitched. Wherein, the image acquisition device is used to perform image acquisition on the wafer in the thickness direction of the wafer, and the first image to be stitched of the multiple initial images and the remaining images of the multiple initial images except the first image to be stitched include the same actual area of the wafer. In this way, by stitching, the target image includes the clear outline of the wafer in the multiple captured initial images, thereby alleviating the situation where there is a large error in the wafer edge measurement due to the large number of blurred outline parts in the image used for wafer contour detection.

[0108] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely illustrative. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architectures, functions and operations of the devices, methods and computer program products according to the multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of the code, and the module, program segment or a part of the code contains one or more executable instructions for implementing the specified logical functions. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or action, or can be implemented using a combination of dedicated hardware and computer instructions.

[0109] In addition, the functional modules in each embodiment of the present application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0110] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard drives, read-only memories (ROM), random access memories (RAM), magnetic disks or optical disks.

[0111] The above description is merely an optional embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. An image acquisition method for wafer contour detection, characterized in that: The method comprises: obtaining a plurality of initial images sequentially captured while the wafer rotates in one direction, wherein an image capture device is used to capture images of the wafer in a thickness direction of the wafer, and a first image to be stitched of the plurality of initial images and remaining images of the plurality of initial images other than the first image to be stitched include a same actual area of the wafer; determining a partial image located within the effective depth of field in each of the multiple initial images except the first image to be stitched as a second image to be stitched; Obtaining a target image for wafer contour detection by performing stitching processing based on each second image to be stitched and the first image to be stitched; The method further comprises: Based on the radius of the wafer and the length of the wafer in the image field of view of the image acquisition device, calculate half the distance between the two end points of the arc of the bow region of the wafer between the image acquisition device and the light source in a top-down view as the target bow length; Determining, according to the target bow length, an area to be stitched in the wafer image captured by the image acquisition device; The method of obtaining a target image for wafer contour detection by performing stitching processing based on each second image to be stitched and the first image to be stitched includes: In the to-be-stitched region of the first to-be-stitched image, each second to-be-stitched image is stitched with the first to-be-stitched image to obtain the target image.

2. The method according to claim 1, characterized in that The method further comprises: In a top-down view, a first target angle corresponding to the effective depth of field is calculated based on the effective depth of field of the image acquisition device and the radius of the wafer, and a first bow height corresponding to the effective depth of field is calculated based on the target angle and the radius; Calculating a first effective depth of field region within the image side field of view according to the coordinates of a midpoint of a wafer edge of the wafer in the image side field of view of the image acquisition device and the first bow height; The determining of a partial image located within the effective depth of field in each of the multiple initial images except the first image to be stitched as a second image to be stitched includes: The partial image corresponding to the first effective depth of field area in each of the other initial images is used as the second image to be stitched.

3. The method according to claim 1, characterized in that The method further comprises: Calculating a second target angle corresponding to the effective depth of field according to half of the effective depth of field of the image acquisition device and the radius of the wafer; Calculating a target arc length according to the second target angle and the radius of the wafer; A sampling rule is set according to the target arc length and / or the resolution of the image acquisition device; wherein, when the sampling rule is set according to the target arc length, when the initial image is acquired using the sampling rule, the arc length corresponding to the angle at which the wafer rotates between two adjacent image acquisitions is less than the target arc length; wherein, when the sampling rule is set according to the resolution of the image acquisition device, when the initial image is acquired using the sampling rule, the difference in actual sizes represented by pixel points of the edge contour within the effective depth of field in the images obtained in two adjacent image acquisitions of the wafer is less than a preset difference; the multiple initial images are obtained by image acquisition based on the sampling rule.

4. The method according to claim 3, characterized in that The obtaining of the multiple initial images sequentially captured while the wafer is rotating in one direction includes: During the rotation of the wafer, determining whether the rotation direction of the wafer is a target direction; When it is determined that the rotation direction of the wafer is the target direction, image acquisition is performed according to the sampling rule to obtain the multiple initial images.

5. The method according to claim 4, characterized in that The performing image acquisition according to the sampling rule to obtain the plurality of initial images includes: After completing one image acquisition, counting is started from 0 according to the pulse signal of the circular grating, and judging whether the sampling time has been reached according to the obtained counting result and the target counting result indicated by the sampling rule, wherein the target counting result is greater than 1; When it is determined that the sampling moment has arrived, image acquisition is performed to obtain an initial image.

6. The method according to claim 1, wherein The wafer is rotated in a direction such that a portion of the wafer within a capture range of the image capture device rotates toward a direction close to the image capture device, and determining a partial image located within an effective depth of field in each of the multiple initial images other than the first image to be stitched as a second image to be stitched includes: Using the latest acquired initial image among the multiple initial images as the first image to be stitched; For each other initial image, a second image to be stitched in the other initial image is determined.

7. An image acquisition device for wafer contour detection, characterized in that: The device comprises: an image acquisition module, configured to acquire a plurality of initial images sequentially acquired while the wafer rotates in one direction, wherein an image acquisition device is configured to acquire images of the wafer in a thickness direction of the wafer, and a first image to be stitched of the plurality of initial images and the remaining images of the plurality of initial images other than the first image to be stitched include a same actual area of the wafer; a determining module, configured to determine a partial image located within an effective depth of field in each of the multiple initial images except the first image to be stitched as a second image to be stitched; a processing module, configured to obtain a target image for wafer contour detection by performing stitching processing based on the second images to be stitched and the first image to be stitched; The device further includes an analysis module, which is configured to: calculate, based on the radius of the wafer and the length of the wafer in the image field of view of the image acquisition device, half the distance between the end points of the arc of the bow region of the wafer between the image acquisition device and the light source at a top-down angle as a target bow length; and determine, based on the target bow length, an area to be spliced in the wafer image acquired by the image acquisition device; The processing module is specifically configured to: perform stitching processing on each second image to be stitched and the first image to be stitched in the stitching area of the first image to be stitched, to obtain the target image.

8. An electronic device, characterized in that: It includes a processor and a memory, wherein the memory stores machine executable instructions that can be executed by the processor, and the processor can execute the machine executable instructions to implement the image acquisition method for wafer contour detection described in any one of claims 1 to 6.

9. A readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the image acquisition method for wafer contour detection according to any one of claims 1 to 6 is implemented.

Images