Image acquisition method for wafer contour detection and related device

Abstract

The invention provides an image acquisition method for wafer contour detection and a related device, and relates to the technical field of wafer detection. The method comprises the steps that a plurality of initial images acquired in sequence in the process that a wafer rotates in one direction are obtained, and image acquisition equipment is used for performing image acquisition on the wafer in the thickness direction of the wafer, the first to-be-spliced image of the plurality of initial images and the remaining images except the first to-be-spliced image in the plurality of initial images comprise the same actual area of the wafer; determining a local image located in the effective depth of field in each of other initial images except the first image to be spliced as a second image to be spliced; and performing splicing processing based on each second to-be-spliced image and the first to-be-spliced image to obtain a target image for wafer contour detection. In this way, the situation that large errors exist in wafer edge measurement due to the fact that the number of fuzzy contour parts in the image used for wafer contour detection is large can be relieved.

Description

Technical Field

[0001] The present application relates to the technical field of wafer detection. Specifically, it relates to an image acquisition method and related device for wafer contour detection. Background Technique

[0002] With the continuous development of the integrated circuit manufacturing process, as the carrier basis of integrated circuits, the processing accuracy of wafers has been continuously improved, making the importance of wafer contour measurement more prominent. Precise contour measurement can ensure the surface quality of wafers, thereby improving the yield and reliability of the entire manufacturing process. In addition, as the process nodes continue to shrink, the lithography process is also more sensitive to minor changes in the wafer contour. Therefore, using advanced measurement techniques to monitor the edge contour of wafers in real time can provide important data support for optimizing the production process and improving product performance.

[0003] Currently, most wafer edge measurements use machine vision-based methods. A contour image including the wafer edge is acquired by a camera, and then the precise edge contour parameters can be calculated by extracting the wafer contour through image processing algorithms. By rotating the wafer around its center, the edge contour morphology in any angular direction of the wafer can be measured. However, due to the influence of various factors, there may be a situation where part of the contour in the contour image acquired by the camera exceeds the effective depth of field range of the camera, that is, part of the contour is blurred, resulting in a large error in wafer edge measurement. Summary of the Invention

[0004] The embodiments of the present application provide an image acquisition method and related device for wafer contour detection. By stitching the local images of the wafer within the depth of field range of multiple images into the same image, the obtained image includes more clear contours of the wafer, thereby alleviating the situation of large errors in wafer edge measurement due to the large number of blurred contour parts in the images for wafer contour detection.

[0005] The embodiments of the present application can be implemented as follows: In a first aspect, the embodiments of the present application provide an image acquisition method for wafer contour detection, the method including: Obtaining multiple initial images sequentially acquired during the rotation of the wafer in one direction, where an image acquisition device is used to acquire 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 except the first image to be stitched include the same actual area of the wafer; Determining the local images within the effective depth of field in each of the other initial images except the first image to be stitched in the multiple initial images as the second images to be stitched; By performing stitching processing based on each second image to be stitched and the first image to be stitched, a target image for wafer contour detection is obtained.

[0006] In a second aspect, an embodiment of the present application provides an image acquisition device for wafer contour detection, the device includes: An image acquisition module, configured to acquire a plurality of initial images sequentially acquired during the rotation of the wafer in one direction. Wherein, the image acquisition device is used to acquire images of the wafer in the thickness direction of the wafer, and the first image to be stitched among the plurality of initial images and the remaining images other than the first image to be stitched among the plurality of initial images include the same actual area of the wafer; A determination module, configured to determine local images located within the effective depth of field in each of the other initial images other than the first image to be stitched among the plurality of initial images as second images to be stitched; A processing module, configured to obtain 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.

[0007] In a third aspect, an embodiment of the present application provides an electronic device, including a processor and a memory, 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 foregoing embodiments.

[0008] In a fourth aspect, an embodiment of the present application provides a readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the image acquisition method for wafer contour detection described in the foregoing embodiments.

[0009] The image acquisition method and related device for wafer contour detection provided by the embodiments of the present application acquire a plurality of initial images sequentially acquired during the rotation of the wafer in one direction, and determine local images located within the effective depth of field in each of the other initial images other than the first image to be stitched among the plurality of initial images as second images to be stitched, and then obtain 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 acquire images of the wafer in the thickness direction of the wafer, and the first image to be stitched among the plurality of initial images and the remaining images other than the first image to be stitched among the plurality of initial images include the same actual area of the wafer. In this way, through stitching, the clear contour of the wafer in the plurality of acquired initial images is included in the target image, thereby alleviating the situation that there are large errors in wafer edge measurement due to the large number of blurred contour parts in the images for wafer contour detection. Description of the Drawings

[0010] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0011] Figure 1 Schematic diagram of a wafer image with edge blurring problems collected by a wafer image acquisition system; Figure 2 Block diagram of an electronic device provided by an embodiment of the present application; Figure 3 One of the flow diagrams of an image acquisition method for wafer contour detection provided by an embodiment of the present application; Figure 4 One of the top views of a wafer at two moments provided by an embodiment of the present application; Figure 5 Another top view of a wafer at two moments provided by an embodiment of the present application; Figure 6 Another flow diagram of an image acquisition method for wafer contour detection provided by an embodiment of the present application; Figure 7 Top view schematic diagram of a wafer; Figure 8 Schematic diagram of a wafer image acquisition system provided by an embodiment of the present application; Figure 9 Sampling timing schematic diagram; Figure 10 Another flow diagram of an image acquisition method for wafer contour detection provided by an embodiment of the present application; Figure 11 Schematic diagram of the position of a wafer in the image plane field of view provided by an embodiment of the present application; Figure 12 Another flow diagram of an image acquisition method for wafer contour detection provided by an embodiment of the present application; Figure 13 One of the block diagrams of an image acquisition device for wafer contour detection provided by an embodiment of the present application; Figure 14 Another block diagram of an image acquisition device for wafer contour detection provided by an embodiment of the present application.

[0012] Icons: 9 - Circular grating; 100 - Electronic device; 110 - Memory; 120 - Processor; 130 - Communication unit; 200 - Image acquisition device for wafer profile detection; 201 - Setting module; 202 - Analysis module; 210 - Image acquisition module; 220 - Determination module; 230 - Processing module. Detailed implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. The components of the embodiments of the present application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0014] 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 claimed present application, but merely represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0015] It should be noted that relational terms such as "first" and "second" are only used 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 "include", "comprise", or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device including a series of elements includes not only those elements but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article, or device including the said element.

[0016] Currently, most wafer edge measurements adopt machine vision-based methods. The telecentric optical system and the parallel coaxial light source in the system for collecting wafer images form 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, through image processing algorithms, the wafer contour can be extracted based on this image, and accurate edge contour parameters can be calculated. The edge contour parameters can include: front top of the edge, front top angle, front top length, rear top, rear top angle, rear top length, etc. By rotating the wafer around its center, the edge contour morphology in any angular direction of the wafer can be measured. Among them, in the above system, an encoder is used to obtain the angle of the wafer.

[0017] Generally, the effective depth of field of telecentric optics is relatively small (usually less than 1 mm). For small-sized wafers (usually wafers with a diameter of less than 8 inches), the radius is small, and most of the bow-shaped area swept by the edge measurement system (i.e., the above-mentioned wafer image acquisition system) can be placed within the effective depth of field, and this measurement method can measure more accurately. However, with the continuous development of camera technology, the size of the camera target surface increases. According to the telecentric optics theory, its effective depth of field will be even smaller (generally below 200 microns).

[0018] With the continuous increase in wafer size, traditional vision measurement of wafer edge profiles has encountered new technical challenges. Limited by the spatial position relationship, the radius of wafers with a size of 12 inches and above is too large, and the width of its bow shape far exceeds the depth of field of the telecentric lens. The problem of edge blurring can be clearly felt in the images obtained by the camera. As Figure 1 shown, the red part in the figure has edge blurring.

[0019] 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 near the center of the circle in the profile is far from the effective depth of field of the telecentric lens, that is, in the camera's field of view, the part near the center of the wafer is not imaged within the effective depth of field of the telecentric lens, which results in a large error in wafer edge measurement.

[0020] To alleviate the above situation, the embodiments of the present application provide an image acquisition method and related device for wafer profile detection. By stitching, the clear edge profile of the wafer in multiple captured initial images is included in the target image, thereby alleviating the situation that there is a large error in wafer edge measurement due to the large number of blurred profile parts in the image for wafer profile detection.

[0021] The following will describe in detail some embodiments of the present application with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0022] Please refer to Figure 2 , Figure 2 which is a schematic block diagram of the electronic device 100 provided by the embodiments of the present application. The electronic device 100 can be, but is not limited to, a computer, a server, etc. 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 achieve data transmission or interaction. For example, these components can be electrically connected to each other through one or more communication buses or signal lines.

[0023] Among them, the memory 110 is used to store programs or data. The memory 110 can be, but is not limited to, a random access memory (RAM), a read only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), etc.

[0024] The processor 120 is used to read / write the data or programs stored in the memory 110 and perform corresponding functions. For example, an image acquisition device 200 for wafer profile detection is stored in the memory 110. The image acquisition device 200 for wafer profile detection includes at least one software function module that can be stored in the memory 110 in the form of software or firmware. The processor 120 executes various functional applications and data processing by running the software programs and modules stored in the memory 110, such as the image acquisition device 200 for wafer profile detection in the embodiments of the present application, thereby implementing the image acquisition method for wafer profile detection in the embodiments of the present application.

[0025] The communication unit 130 is used to establish a communication connection between the electronic device 100 and other communication terminals through a network and is used to transmit and receive data through the network.

[0026] 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 further include more or fewer components than those shown Figure 2 in the figure, or have a different configuration from that shown Figure 2 in the figure. Figure 2 Each component shown in the figure can be implemented by hardware, software, or a combination thereof.

[0027] Please refer to Figure 3 , Figure 3 which is one of the schematic flowcharts of the image acquisition method for wafer profile detection provided by the embodiments of the present application. The method can be applied to the above-mentioned electronic device. The specific process of the image acquisition method for wafer profile detection will be elaborated in detail below. In this embodiment, the method may include steps S210 to S230.

[0028] Step S210: Obtain multiple initial images sequentially acquired during the rotation of the wafer in one direction.

[0029] Step S220: Determine the partial images within the effective depth of field in each of the other initial images among the multiple initial images except the first image to be stitched as the second images to be stitched.

[0030] Step S230: Obtain a target image for wafer contour detection by performing stitching processing based on each of the second images to be stitched and the first image to be stitched.

[0031] In this embodiment, during the rotation of the wafer in one direction, an image acquisition device with a fixed position is used to acquire images of the wafer, thereby obtaining the multiple initial images. The multiple initial images are obtained by the image acquisition device to acquire images of the wafer in the thickness direction of the wafer. One of the multiple initial images is used as the first image to be stitched. The first image to be stitched and the remaining images among the multiple initial images (the remaining images may include one initial image or multiple initial images) include the same actual area of the wafer, that is, a part of the entity of the wafer appears in both the first image to be stitched and the remaining images among the multiple initial images except the first image to be stitched. Each of the multiple initial images except the first image to be stitched is used as an other initial image. Optionally, the first stitched image and each of the other initial images form a group of images. It is possible that there is the same actual area of the wafer in some groups of images and there is no same actual area of the wafer in the remaining groups of images, or there is the same actual area of the wafer in each group of images, which can be determined by the way of obtaining the multiple initial images. In the groups of images with the same actual area of the wafer, the same actual area of the wafer in each group of images may be different. The first image to be stitched is the reference image for subsequent stitching, that is, other images are stitched onto the first image to be stitched.

[0032] Optionally, 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 above multiple initial images. Or, 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 multiple initial images are determined from the stored images.

[0033] For each of the other initial images, the partial image within the effective depth of field in the other initial image can be determined as a second image to be stitched by any method. For example, by analyzing the contour situation in the image or by other methods, the second image to be stitched in an other initial image is determined.

[0034] After that, splicing processing can be performed based on each second image to be spliced and the first image to be spliced, so as to correct the unclear edge contour in the first image to be spliced based on the edge contour indicated by the corresponding second image to be spliced, thereby obtaining a target image for wafer contour detection. In this way, a clearly visible edge contour can be spliced, so that the obtained target image includes more clear contours of the wafer, thereby alleviating the situation that there are large errors in wafer edge measurement due to the large number of blurred contour parts in the image for wafer contour detection.

[0035] Based on the spatial position relationship between the wafer and the telecentric system and the motion characteristics of the wafer rotating around its center, it can be known from Figure 4 that at a certain moment t, the camera (i.e., the image acquisition device in Figure 4 ) can obtain a clear contour of point B, but the obtained contour of point A is relatively blurred, and the contour below point A is particularly blurred. Due to the position occlusion relationship, the contour of C cannot be obtained; in the counterclockwise rotation mode, when the wafer rotates to the moment t + 1, the camera can obtain a clear contour of point E, but the obtained contour of point D is relatively blurred, and due to the position occlusion relationship, the contour of F cannot be obtained. Point C at moment t is between points E and F at moment t + 1, point B at moment t is between points D and E at moment t + 1, and point A at moment t is between points D at moment t + 1. From this, it can be seen that the original point A jumps out of the telecentric optical field of view. At moment t + 1, the camera obtains a clear contour of point E, but cannot obtain a clear contour of point A. Among them, Figure 4 the light source in Figure 4 is used to provide brightness for image acquisition;

[0036] Through the above processing of this solution, by splicing the local images of the wafer within the depth of field range of multiple images into the same image, the contour of point A at moment t can be used to replace the contour of point A at moment t + 1, and a complete and clear wafer edge contour can be obtained. Repeating this process can obtain the effective edge of the wafer and improve the accuracy of wafer edge measurement. It can be understood that Figure 4 is only an exemplary illustration, and the specific position of the clear contour point in the previous moment image in the image of the next moment can be determined according to the actual situation.

[0037] For example, as shown in Figure 5 , in the counterclockwise rotation mode, when the wafer rotates to the moment t + 1, the situation can be: point C is at the original position of point B, point B is at the original position of point A, and the original point A jumps out of the telecentric optical field of view. At this time, the camera obtains an effective contour of the original point C, but cannot obtain an effective contour of the original point B. Similarly, at moment t + 1, the contour of point B at moment t can be used to replace the contour of point B at this time, and a complete and clear wafer edge contour can be obtained.

[0038] In this embodiment, before image acquisition, a sampling rule may be set first. The sampling rule is used to indicate the manner of image acquisition. For example, the sampling rule includes a sampling frequency, and subsequent image acquisition can be performed according to this sampling frequency to obtain multiple initial images. Among them, the specific value of the sampling frequency can be determined in combination with actual requirements.

[0039] Please refer to Figure 6 , Figure 6 which is the second flowchart of the image acquisition method for wafer contour detection provided by the embodiment of the present application. In this embodiment, on the basis of Figure 3 shown, before step S210, the method may further include steps S111 to S113, and the sampling rule can be determined through steps S111 to S113.

[0040] Step S111: Calculate the 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.

[0041] Step S112: Calculate the target arc length according to the second target angle and the radius of the wafer.

[0042] Step S113: Set the sampling rule according to the target arc length and / or the resolution of the image acquisition device.

[0043] In this embodiment, from the foregoing Figure 4 and Figure 5 , it can be seen that half of the wafer located 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 according to 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 within half of the effective depth of field. Then, the arc length of the sector in the wafer with this second target angle as the sector angle can be calculated as the target arc length. Then, the sampling rule can be set according to the target arc length and / or the resolution of the image acquisition device, and this sampling rule can include a sampling frequency.

[0044] Among them, optionally, when setting the sampling rule considering the target arc length, when performing image acquisition based on this sampling rule to obtain the initial image, the arc length corresponding to the rotation angle of the wafer between two adjacent image acquisitions is less than the target arc length. In this way, it is possible to avoid the situation where the continuous contours in the target image appear as clear contours, unclear contours, and clear contours in sequence after splicing, thus ensuring the splicing effect.

[0045] Please refer to Figure 7 , Figure 7It is a top view schematic diagram of a wafer. Assuming that the effective depth of field of the lens is 2m, then half of the effective depth of field is 1m; at the same time, assuming that the radius of the wafer is r, then the second target angle is: . The target arc length corresponding to half of the effective depth of field is: . When setting the sampling rule based on this target arc length, the arc length corresponding to the angle by which the wafer rotates between two adjacent image acquisitions is less than the target arc length .

[0046] As Figure 4 shown, assume 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. When setting the sampling rule based on the target arc length, that is, the arc length corresponding to the angle by which the wafer rotates between 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, there is at least one overlapping point between arc AB and arc DE. In this way, after splicing with the image obtained at time t + 1 as the splicing base image, there is no blurred contour edge in arc AE.

[0047] 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, and A > B. Since splicing requires splicing images obtained at different times, in order to avoid a large difference in the actual sizes corresponding to the pixel points of the contour edges after splicing, the sampling rule can be set in combination with the resolution of the image acquisition device, so that the difference in the actual sizes corresponding to the pixel points of the second image to be spliced in the initial images obtained from two adjacent image acquisitions is within a certain range. Optionally, when setting the sampling rule according to the resolution of the image acquisition device, when using the sampling rule to acquire the initial image, the difference in the actual sizes represented by the pixel points of the edge contour within the effective depth of field in the images obtained by the wafer in two adjacent image acquisitions is less than a preset difference.

[0048] Optionally, when the sampling rule indicates the sampling frequency, image acquisition can be carried out in combination with the rotation of the wafer. Optionally, as Figure 8 shown, a circular grating 9 can be added at the wafer fixing place of a conventional wafer image acquisition system to accurately determine the angular position relationship of the wafer at time t. The circular grating signal of the circular grating can be used for both the closed-loop control of the servo system and image splicing (i.e., the image acquisition part). That is, the TTL signal (i.e., A+ / A-, B+ / B-) of the circular grating is divided into two paths. One path is connected to the servo motor that drives the wafer to rotate for its closed-loop control use, and the other path is connected to the external trigger signal of the image acquisition device to drive the image acquisition device to sample to obtain the initial image.

[0049] In this embodiment, during the rotation of the wafer, it can be determined whether the rotation direction of the wafer is the 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. In this way, it is possible to avoid the poor stitching result caused by sampling when the rotor driving the wafer to rotate retreats. Optionally, the rotation direction of the wafer can be judged according to the phase relationship of A+ / A-, B+ / B-.

[0050] In image acquisition, sampling can be controlled according to the pulse signal of the circular grating. After the first image acquisition or after completing an image acquisition, counting can start from 0 according to the pulse signal of the circular grating, and it is judged whether the sampling moment is reached according to the obtained counting result and the target counting result indicated by the sampling rule. The target counting result is greater than 1. When it is determined that the sampling moment is reached, an initial image is obtained through image acquisition. In this way, it is possible to avoid a large amount of processing caused by frequent image acquisition. After the image acquisition device receives the circular grating signal, it can sample according to the frequency division algorithm according to the sampling timing.

[0051] Among them, assuming that the rotation speed of the wafer is ω and the number of times the circular grating is triggered when the wafer rotates one week is T, then the angle φ that the wafer turns through each pulse is φ = 2π / T, and the arc length turned through in the circumferential direction is: ; assuming that the target counting result is N, then based on the target arc length When setting the target counting result N, based on this condition Set the target counting result N.

[0052] In this embodiment, the rotation direction of the wafer is such that the part of the wafer within the acquisition range of the image acquisition device rotates towards the direction close to the image acquisition device, so that subsequent stitching can be performed. That is to say, the rotation direction of the wafer must satisfy that when looking down at the surface of the wafer, the linear velocity direction of the part in the central optical system points to the camera. When it points away from the camera, dynamic stitching cannot be performed. As Figure 5 shown, the image acquisition device is below, the left side of the wafer is within the acquisition range of the image acquisition device, and the rotation direction of the wafer must be counterclockwise. Under this rotation mode requirement, the latest acquired 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, and for each other initial image, the second image to be stitched in this other initial image is determined.

[0053] Optionally, the image acquisition device can judge the rotation direction of the wafer through the phase relationship of A+ / A-, B+ / B- to achieve two-term one-increment trigger sampling, so as to effectively avoid the error caused by the wafer position jitter.

[0054] The following combines Figure 9, an example is given to illustrate how to collect images.

[0055] When the circular grating rotates, it will send out three-phase pulse signals A, B, and Z. Figure 9 The A and B phases shown by a and b in 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 9 As shown in b, when rotating clockwise, signal A leads signal B by 1 / 4 cycle; when rotating counterclockwise, signal B leads signal A by 1 / 4 cycle. Each pulse of the two pulse signals A and B corresponds to a fixed mechanical angle increment, such as one pulse corresponding to 0.001°. The total displacement, that is, the rotation angle, can be calculated by counting the number of pulses. The Z signal is an index signal, which generates a pulse every rotation to mark the origin and is used to eliminate or calibrate the accumulated error.

[0056] like Figure 9 As shown in b, through the pulse rules of the two signals A and B, Figure 9 The b in is divided into two parts.

[0057] 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 rotates 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.

[0058] This solution requires that data be collected while the wafer rotates in the same direction to ensure that the collected wafer position and 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 rear part rotates counterclockwise, it means that the wafer has rotated. At this time, if the counting continues, the position collection will be repeated, which cannot correspond to the actual situation, so the count needs to be reduced.

[0059] Figure 9 The "count" in b is the same as Figure 9It corresponds to N in a and is used to control the sampling density. That is, after A and B signals generate N pulses, a data sampling (i.e., an image acquisition) is performed. The smaller the value of N, the denser the sampling; the larger the value of N, the sparser the sampling. In theory, the smaller the value of N, the better. However, there are various restrictive factors, such as: 1. If the value of N is too small, the sampling will be denser, resulting in too much measurement data, slow data processing, and affecting the measurement rhythm; 2. Generally, the single-sampling time of the sensor remains unchanged. If N takes the minimum value of 1, the grating pulse period must be not less than the single-sampling time, then the grating rotation must be slower, affecting the measurement rhythm; 3. If the value of N is too small, the error of the grating itself will be transmitted to the measurement result; the larger N is, the errors of N pulses will accumulate with each other to eliminate part of the error; when N takes the maximum value (the number of pulses for one circle of grating rotation), the grating rotation period error will disappear.

[0060] Considering the above restrictive factors and balancing the measurement accuracy and the measurement rhythm, the following settings can be made: , where T1 is the sampling time and T0 is the pulse period of the A and B phases of the circular grating.

[0061] In addition, considering that the data needs to be saved, processed, and analyzed in a timely manner after obtaining a single sampling data, in order to ensure the accuracy of the data, the data analysis and processing need to be completed before the next sampling ends, to avoid new data being stored before the previous data processing is completed. This is also one of the factors affecting N, and the following settings can be made: , that is, the minimum value of the aforementioned target count result is .

[0062] Please refer to Figure 10 , Figure 10 This is the third flowchart of the image acquisition method for wafer profile detection provided by the embodiment of the present application. In this embodiment, on the basis of Figure 3 shown, the method may further include step S121 to step S122. As a possible implementation, steps S121 to S122 may be executed before the second image to be stitched in a first determined other initial image is determined, that is, before step S220, so as to quickly determine the second image to be stitched in each other initial image.

[0063] Step S121, from a top view angle, according to the effective depth of field of the image acquisition device and the radius of the wafer, calculate the first target angle corresponding to the effective depth of field, and calculate the first sagitta corresponding to the effective depth of field according to the target angle and the radius.

[0064] Step S122, according to the coordinates of the midpoint of the wafer edge in the wafer image collected by the image acquisition device and the first sagitta, calculate the effective depth of field area corresponding to the wafer image.

[0065] From the top-down perspective, based on the effective depth of field of the image acquisition device and the radius of the wafer, the first target angle corresponding to the effective depth of field can be calculated. At a certain moment, a schematic diagram of the wafer from the top-down perspective is as shown in Figure 7 shown, and its position in the camera's field of view is as shown in Figure 11 shown. As shown in Figure 7 shown, this first target angle can be the angle calculated based on half of the effective depth of field of 2m and the radius r of the wafer: .

[0066] Assume that the camera's field of view (i.e., the image-side field of view) of the image acquisition device is W*H, and the position of the wafer in this field of view is as shown in Figure 11 shown, and the coordinates of the midpoint of the wafer edge in the image-side field of view are (a, b). Then the first sagitta is: , and then the first effective depth of field region in the image-side field of view can be calculated as . That is, the images within the range of in the image-side field of view are within the effective depth of field and do not need to be replaced by stitching, while the images in the remaining ranges need to be dynamically stitched.

[0067] After determining the first effective depth of field region in the image-side field of view, the local images corresponding to the first effective depth of field region 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 region, the first effective depth of field region in the image-side field of view can be directly converted to the image coordinate system used for the acquired wafer images to obtain the second effective depth of field region, and then the images in each of the other initial images located within the second effective depth of field region can be directly used as the second images to be stitched. In this way, by determining the first effective depth of field region in advance, the second images to be stitched in each of the initial images can be quickly determined based on this first effective depth of field region.

[0068] Optionally, in this embodiment, before stitching, the region to be stitched in the first image to be stitched can also be determined, and then stitching can be performed within this region to be stitched. Please refer to Figure 12 , Figure 12 which is the fourth flowchart of the image acquisition method for wafer contour detection provided by the embodiment of the present application. In this embodiment, based on what is shown in Figure 3 shown, before stitching, that is, before step S230, the method can further include steps S131 to S132, and then the region to be stitched in the first image to be stitched can be directly determined each time stitching is performed.

[0069] Step S131: Calculate half of the distance between the two endpoints of the arc of the bow-shaped area where the wafer is located between the image acquisition device and the light source from the top-down perspective based on the radius of the wafer and the length of the wafer in the image space field of view of the image acquisition device, and use it as the target bow length.

[0070] Step S132: Determine the area to be stitched in the wafer image acquired by the image acquisition device according to the target bow length.

[0071] In this embodiment, as Figure 11 shown, assuming that the image space field of view of the image acquisition device is W*H, and the coordinates of the midpoint of the wafer edge in the image space field of view of the image acquisition device are (a, b), then the length of the wafer appearing in the image space field of view is: . Then, the target bow length is as Figure 7 shown, and is: , . In the case where the wafer rotates counterclockwise, the sector PQO can be used as the initial area to be stitched, where P is the midpoint of the wafer edge, O represents the center of the wafer, and the distance from Q to the straight line OP is the target bow length s. The above initial area to be stitched can be converted to the coordinate system used in the wafer image acquired by the image acquisition device, so as to obtain the area to be stitched in the wafer image. Then, when stitching an initial image as the first image to be stitched, in the area to be stitched of the first image to be stitched, each second image to be stitched can be stitched with the first image to be stitched to obtain the target image.

[0072] Optionally, for each second image to be stitched, registration can be performed on the second image to be stitched and the first image to be stitched, or the other initial images where the second image to be stitched is located can be registered with the first image to be stitched to obtain the transformation matrix corresponding to the second image to be stitched. Then, according to the transformation matrices corresponding to the second images to be stitched, the second images to be stitched can be converted to the coordinate system of the first image to be stitched, and then the converted second images to be stitched can be used to replace the corresponding blurred local wafer images in the first image to be stitched.

[0073] Among them, in the case where the area to be stitched in the first image to be stitched is determined, in this area to be stitched, the converted second images to be stitched are used to replace the corresponding blurred local wafer images in the first image to be stitched.

[0074] The above image acquisition method for wafer profile detection provided by this embodiment is a method for dynamically splicing edge pixels in wafer profile vision measurement, which can splice a clearly visible edge profile in the target image, reduce the blurred profile in the image for wafer profile detection, and thus greatly improve the measurement accuracy of the wafer profile edge.

[0075] To execute the corresponding steps in the above embodiments and various possible ways, the following presents an implementation of an image acquisition device 200 for wafer profile detection. Optionally, the image acquisition device 200 for wafer profile detection may adopt the device structure of the electronic device shown above. Further, please refer to Figure 2 the Figure 13 Figure 13 FIG. 9 is one of the block diagrams of the image acquisition device 200 for wafer profile detection provided by an embodiment of the present application. It should be noted that the basic principle and the technical effects generated by the image acquisition device 200 for wafer profile detection provided in this embodiment are the same as those in the above embodiments. For a brief description, for the parts not mentioned in this embodiment, reference may be made to the corresponding content in the above embodiments. The image acquisition device 200 for wafer profile detection may include: an image acquisition module 210, a determination module 220, and a processing module 230.

[0076] The image acquisition module 210 is configured to acquire a plurality of initial images sequentially acquired during the rotation of the wafer in one direction. Among them, 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 spliced among the plurality of initial images and the remaining images other than the first image to be spliced among the plurality of initial images include the same actual area of the wafer.

[0077] The determination module 220 is configured to determine local images located within the effective depth of field in each of the other initial images other than the first image to be spliced among the plurality of initial images as the second images to be spliced.

[0078] The processing module 230 is configured to obtain a target image for wafer profile detection by performing splicing processing based on each second image to be spliced and the first image to be spliced.

[0079] Please refer to Figure 14 Figure 14 FIG. 10 is a second block diagram of the image acquisition device 200 for wafer profile detection provided by an embodiment of the present application. In this embodiment, on the basis of the image acquisition device 200 for wafer profile detection shown in Figure 13 FIG. 9, the image acquisition device 200 for wafer profile detection may further include a setting module 201 and an analysis module 202.

[0080] ​​The setting module 201 is used to: calculate 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; calculate a target arc length according to the second target angle and the radius of the wafer; set a sampling rule 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 edge contours of the wafer located within the effective depth of field in 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.

[0081] 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 of the wafer in the image side field of view of the image acquisition device in the image side field of view and the first bow height.

[0082] 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.

[0083] 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 two end points of the arc of the arch area of ​​the wafer between the image acquisition device and the light source at a top-down angle as a target arch length; and determine, based on the target arch length, the area to be spliced ​​in the wafer image captured by the image acquisition device.

[0084] 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, so as to obtain the target image.

[0085] Optionally, the above modules can be stored in the form of software or firmware. Figure 2 The memory 110 shown in the figure may be fixed in the operating system (OS) of the electronic device 100 and may be Figure 2It is executed by the processor 120 in []. Meanwhile, the data, program code, etc. required for executing the above modules can be stored in the memory 110.

[0086] An embodiment of the present application also provides a readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the image acquisition method for wafer profile detection described above is implemented.

[0087] In summary, an embodiment of the present application provides an image acquisition method and related device for wafer profile detection, obtaining multiple initial images sequentially acquired during the rotation of the wafer in one direction, and determining local images within the effective depth of field in each of the other initial images except the first image to be stitched among the multiple initial images as the second images to be stitched. Then, through stitching processing based on each of the second images to be stitched and the first image to be stitched, a target image for wafer profile detection is obtained. Among them, the image acquisition device is used to acquire images of the wafer in the thickness direction of the wafer, and the first image to be stitched among the multiple initial images and the remaining images except the first image to be stitched among the multiple initial images include the same actual area of the wafer. In this way, through stitching, the clear profile of the wafer in multiple acquired initial images is included in the target image, thereby alleviating the situation that there are large errors in wafer edge measurement due to many blurred profile parts in the images for wafer profile detection.

[0088] In several embodiments provided by the present 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 devices, methods, and computer program products according to multiple embodiments of the present application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0089] In addition, each functional module in various embodiments of the present application may be integrated together to form an independent part, or each module may exist alone, or two or more modules may be integrated to form an independent part.

[0090] If the above-mentioned function is implemented in the form of a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0091] The above are only optional embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope 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 acquired during a process in which the wafer rotates in one direction, wherein an image acquisition device is used 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 except the first image to be stitched include a same actual area of ​​the wafer; 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; By performing stitching processing based on each of the second images to be stitched and the first images to be stitched, a target image for wafer contour detection is obtained.

2. The method according to claim 1, characterized in that The method further comprises: At a top-down angle, according to the effective depth of field of the image acquisition device and the radius of the wafer, a first target angle corresponding to the effective depth of field is calculated, and according to the target angle and the radius, a first bow height corresponding to the effective depth of field is calculated; Calculate a first effective depth of field region within the image side field of view according to the coordinates of the midpoint of the wafer edge of the wafer in the image side field of view of the image acquisition device in the image side field of view and the first bow height; The step of 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 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: According to the radius of the wafer and the length of the wafer in the image field of view of the image acquisition device, half of the distance between the two end points of the arc of the arc-shaped area where the wafer is located between the image acquisition device and the light source at a top-view angle is calculated as the target arch length; According to the target bow length, determining the area to be spliced ​​in the wafer image acquired 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.

4. 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 edge contours located within the effective depth of field in images obtained from two adjacent image acquisitions of the wafer is less than a preset difference; the multiple initial images are acquired by performing image acquisition based on the sampling rule.

5. The method according to claim 4, characterized in that The obtaining of the multiple initial images acquired sequentially during the process of the wafer rotating in one direction comprises: 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.

6. The method according to claim 5, characterized in that The performing image acquisition according to the sampling rule to obtain the multiple 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 is 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 time has been reached, image acquisition is performed to obtain an initial image.

7. The method according to claim 1, characterized in that The rotation direction of the wafer makes the portion of the wafer located within the acquisition range of the image acquisition device rotate toward the direction close to the image acquisition device, and the determining of the partial images 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 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.

8. An image acquisition device for wafer contour detection, characterized in that: The device comprises: An image acquisition module, used for acquiring a plurality of initial images sequentially acquired during the process of the wafer rotating in one direction, wherein an image acquisition device is used for acquiring images of the wafer in a thickness direction of the wafer, and a first image to be spliced ​​of the plurality of initial images and the remaining images of the plurality of initial images except the first image to be spliced ​​include a same actual area of ​​the wafer; A determination module, configured to determine 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 a second image to be stitched; The processing module is used to obtain 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.

9. An electronic device, characterized in that: It comprises 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 as described in any one of claims 1-7.

10. 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 as described in any one of claims 1 to 7 is implemented.

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