Overlay measurement imaging brightness adjusting method and related equipment

Abstract

The invention discloses an overlay measurement imaging brightness adjusting method and related equipment, and relates to the technical field of overlay measurement. Acquiring an initial image of an overlay mark area in the wafer according to the initial imaging parameters; and if detecting that the gray information of the overlay mark area in the initial image does not meet the preset condition, adjusting the initial camera exposure time to be the first camera exposure time according to the corresponding relationship between the camera exposure time and the gray information. And if the exposure time of the first camera meets the exposure condition, controlling the camera to collect an image of the overlay mark according to the exposure time of the first camera and the gear of the initial light source attenuation piece. According to the method and the device, parameter adjustment can be performed on each overlay mark in the wafer, the brightness of each overlay mark image is ensured to meet the requirement, and the measurement accuracy of each overlay mark is further improved.

Description

Technical Field

[0001] The present application relates to the technical field of overlay measurement, and more specifically, to an overlay measurement imaging brightness adjustment method and related equipment. Background Art

[0002] Overlay measurement ensures the precise alignment and placement of each layer of graphics with the previous layer by accurately measuring and calibrating the overlay marks on the wafer during the lithography process, ensuring that the chips after cutting the wafer meet the alignment accuracy and avoiding performance problems of the chips after cutting. At present, the image or diffraction signal of the overlay mark is collected by using the principle of optical imaging or diffraction, and the position deviation between each overlay mark is analyzed on the image or diffraction signal to obtain the overlay measurement result.

[0003] However, due to the non-uniformity of the process in the wafer manufacturing process, such as photolithography coating, etching, mechanical grinding and other process steps, there will be structural differences between the areas where different overlay marks are located in the wafer, and these differences will cause differences in reflectivity in different areas. Therefore, if a fixed exposure time and light source brightness are used for overlay measurement, due to the difference in reflectivity in different areas, the brightness of the collected images will be different, and the images of some marks may be too bright or too dark, affecting the accuracy and stability of the overlay measurement results.

[0004] Therefore, there is an urgent need for a method for adjusting the imaging brightness of overlay measurement so that the imaging brightness of the overlay mark is within a reasonable range, thereby improving the accuracy and stability of the overlay measurement. Summary of the invention

[0005] In view of the above problems, the present application provides an overlay measurement imaging brightness adjustment method and related equipment to achieve the purpose of keeping the brightness of the collected overlay mark imaging within a reasonable range, thereby improving the accuracy and stability of the overlay measurement. The specific scheme is as follows:

[0006] The first aspect of the present application provides a method for adjusting the brightness of an overlay measurement imaging, comprising:

[0007] Acquire an initial image of the wafer to be measured, wherein the initial image is acquired by controlling a camera of an overlay measurement device according to pre-set initial imaging parameters, wherein the initial image includes an overlay mark area where an overlay mark is located, and the initial imaging parameters at least include: an initial camera exposure time and an initial light source attenuation profile;

[0008] When the grayscale information of the overlay mark area does not meet the preset condition, adjusting the initial camera exposure time to the first camera exposure time according to the corresponding relationship between the camera exposure time and the grayscale information;

[0009] When the exposure time of the first camera meets the exposure condition, the exposure time of the first camera and the initial light source attenuation plate position are used as imaging parameters to control the camera to perform an acquisition operation.

[0010] In a possible implementation, when the exposure time of the first camera does not meet the exposure condition, the overlay measurement imaging brightness adjustment method further includes:

[0011] According to the correspondence between the light source attenuation sheet position and the grayscale information, adjusting the initial light source attenuation sheet position to the first light source attenuation sheet position;

[0012] The initial camera exposure time and the first light source attenuation sheet position are used as imaging parameters to control the camera to perform an acquisition operation.

[0013] In a possible implementation, the exposure condition is: the exposure time of the first camera is within a preset exposure time threshold range, and the preset exposure time threshold range is determined according to an exposure time range allowed by the hardware structure of the camera.

[0014] In one possible implementation, the correspondence between the camera exposure time and the grayscale information is a correspondence determined by the inverse relationship between the camera exposure time that makes the grayscale information of the overlay mark area after the adjustment meet the preset conditions and the grayscale information of the overlay mark area in the initial image, and the grayscale information is used to characterize the brightness of different pixel points in the area where the overlay mark is located.

[0015] In a possible implementation, the correspondence between the light source attenuation plate gear position and the grayscale information is a correspondence determined by the inverse relationship between the light source attenuation plate gear position that makes the grayscale information of the overlay mark area after adjustment meet preset conditions and the grayscale information of the overlay mark area in the initial image.

[0016] In a possible implementation, adjusting the initial camera exposure time to the first camera exposure time according to the correspondence between the camera exposure time and the grayscale information includes:

[0017] Calling a preset exposure time adjustment relational expression characterizing the correspondence between camera exposure time and grayscale information, wherein the exposure time adjustment relational expression is an expression of camera exposure time with respect to grayscale information of the overlay mark area, wherein the camera exposure time is equal to a quotient of an exposure parameter and the grayscale information of the overlay mark area, and the exposure parameter is the product of a preset grayscale information limit value and the initial camera exposure time;

[0018] Determining a first camera exposure time corresponding to the grayscale information of the overlay mark area according to the exposure time adjustment relationship;

[0019] The initial camera exposure time is adjusted to the first camera exposure time.

[0020] In a possible implementation, adjusting the initial light source attenuation sheet position to the first light source attenuation sheet position according to the correspondence between the light source attenuation sheet position and the grayscale information includes:

[0021] Calling a preset light source attenuation sheet position adjustment relational expression that characterizes the correspondence between the light source attenuation sheet position and the grayscale information, wherein the light source attenuation sheet position adjustment relational expression is an expression of the light source attenuation sheet position with respect to the grayscale information of the overlay mark area, wherein the light source attenuation sheet position is equal to the quotient of the attenuation sheet position parameter and the grayscale information of the overlay mark area, and the attenuation sheet position parameter is the quotient of a preset grayscale information limit value and the initial light source attenuation sheet position;

[0022] Determine the undetermined light source attenuation plate gear position corresponding to the grayscale information of the overlay mark area according to the light source attenuation plate gear position adjustment relationship;

[0023] Get the gear list of the light source attenuation sheet gear;

[0024] From the gear list, a light source attenuation plate gear that is closest to the undetermined light source attenuation plate gear is determined as the first light source attenuation plate gear.

[0025] In a possible implementation, the process of detecting the grayscale information of the overlay mark area in the initial image captured by the camera according to the preset initial imaging parameters includes:

[0026] Grayscale recognition processing is performed on the overlay mark area in the initial image to obtain the grayscale of the overlay mark area as grayscale information of the overlay mark area.

[0027] In a possible implementation, performing grayscale recognition processing on the overlay mark area in the initial image to obtain the grayscale of the overlay mark area includes:

[0028] Identifying an inner region and an outer region of the overlay mark region in the initial image;

[0029] Dividing the inner layer area and the outer layer area into a preset number of ROI areas respectively;

[0030] Performing grayscale recognition on each of the ROI regions respectively to obtain the ROI grayscale of each of the ROI regions;

[0031] The average value of the ROI grayscales corresponding to all the ROI regions is determined as the grayscale of the region where the overlay mark is located in the initial image.

[0032] A second aspect of the present application provides an overlay measurement imaging brightness adjustment device, comprising:

[0033] An initial image acquisition unit is used to acquire an initial image of the wafer to be measured, wherein the initial image is acquired by controlling the camera of the overlay measurement device according to preset initial imaging parameters, wherein the initial image includes an overlay mark area where the overlay mark is located, and the initial imaging parameters at least include: initial camera exposure time and initial light source attenuation profile;

[0034] an exposure time adjustment unit, configured to adjust the initial camera exposure time to a first camera exposure time according to a correspondence between camera exposure time and grayscale information when the grayscale information of the overlay mark area does not meet a preset condition;

[0035] The control acquisition unit is used to control the camera to perform an acquisition operation by taking the exposure time of the first camera and the initial light source attenuation sheet position as imaging parameters when the exposure time of the first camera meets the exposure condition.

[0036] The third aspect of the present application provides an overlay measurement imaging brightness adjustment device, comprising at least one processor and a memory connected to the processor, wherein:

[0037] The memory is used to store computer programs;

[0038] The processor is used to execute the computer program so that the overlay measurement imaging brightness adjustment device can implement the overlay measurement imaging brightness adjustment method of the above-mentioned first aspect or any implementation manner of the first aspect.

[0039] In a fourth aspect, the present application provides a computer storage medium, which carries one or more computer programs. When the one or more computer programs are executed by an overlay measurement imaging brightness adjustment device, the overlay measurement imaging brightness adjustment device can implement the overlay measurement imaging brightness adjustment method of the above-mentioned first aspect or any implementation of the first aspect.

[0040] The fifth aspect of the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the overlay measurement imaging brightness adjustment method of the above-mentioned first aspect or any implementation method of the first aspect.

[0041] It can be seen from the above technical solutions that the overlay measurement imaging brightness adjustment method provided in the embodiment of the present application, when it is detected that the overlay mark image currently collected according to the initial imaging parameters has an image brightness that does not meet the preset requirements, adjusts the camera exposure time according to the correspondence between the grayscale information of the overlay mark area and the camera exposure time to adjust the brightness of the image collected subsequently. However, considering the limitations of the camera exposure conditions, when the first camera exposure time meets the exposure condition, then.

[0042] Based on this, compared with the prior art of capturing the image of each overlay mark with fixed camera parameters, the present application can adjust parameters for each overlay mark in the wafer to be measured when performing overlay measurement, ensuring that the brightness of each overlay mark image meets the requirements, and performing overlay measurement based on the overlay mark image that meets the brightness requirements, thereby further improving the accuracy of the measurement of each overlay mark. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0044] Figure 1 A schematic diagram of a flow chart of a method for adjusting the brightness of overlay measurement imaging provided in an embodiment of the present application;

[0045] Figure 2 An example diagram of a grayscale recognition ROI area provided in an embodiment of the present application;

[0046] Figure 3 Another example diagram of grayscale recognition of ROI area provided in an embodiment of the present application;

[0047] Figure 4 A schematic diagram of a light source attenuation sheet provided in an embodiment of the present application;

[0048] Figure 5 A schematic diagram of the structure of an overlay measurement imaging brightness adjustment device provided in an embodiment of the present application;

[0049] Figure 6 A schematic structural diagram of an overlay measurement imaging brightness adjustment device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in 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. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0051] It is understandable that due to the differences in manufacturing processes between wafers or silicon slices, there are structural differences between different wafers and between different regions of the same wafer. As a result, when the imaging overlay measurement equipment uses a uniform camera exposure time and light source brightness to perform overlay measurement on the wafer, there are differences in the imaging brightness of the wafer. Some images may be too bright or too dark, affecting the clarity of the image and thus the accuracy of the overlay measurement results.

[0052] Based on this, an embodiment of the present application proposes a method for adjusting the brightness of overlay measurement imaging, which is applied to an imaging overlay measurement device. When the imaging overlay measurement device performs overlay measurement on each overlay mark of the wafer to be measured, the imaging parameters and light source of the camera of the imaging overlay measurement device are preferentially adjusted based on this method, so that the camera parameters, light source environment, etc. can adapt to the reflectivity of the structure of each overlay mark in the current wafer to be measured to the light source, so that the final overlay mark can be clearly imaged, thereby improving the accuracy of the overlay measurement of the wafer to be measured.

[0053] Reference Figure 1 , a flow chart of a method for adjusting the brightness of overlay measurement imaging provided in an embodiment of the present application is provided, and the implementation process of the method for adjusting the brightness of overlay measurement imaging is described. Specifically, the following steps may be included:

[0054] Step S110 , obtaining an initial image of the wafer to be measured, wherein the initial image is acquired by controlling a camera of an overlay measurement device according to preset initial imaging parameters.

[0055] During the integration and adjustment stage of the imaging overlay measurement equipment, an initial measurement state is usually calibrated using optical methods, wherein the initial measurement state calibrates the initial imaging parameters, which may specifically include: initial camera exposure time and initial light source attenuation sheet position, and optionally, may also include: focal length, aperture position, etc.

[0056] Optionally, each time the wafer to be tested is tested in the embodiment of the present application, the imaging overlay measurement equipment will be adjusted accordingly. It is possible that the imaging overlay measurement will not restore the calibrated measurement state after each measurement. Therefore, for this measurement, the state of the imaging overlay measurement equipment when the wafer was last measured is the initial imaging state of this measurement. The imaging parameters obtained by adjusting the wafer when it was last measured can be used as the initial imaging parameters of this measurement.

[0057] Furthermore, the imaging overlay measurement device collects images of the overlay marks to be measured in the wafer to be measured based on the initial imaging parameters of the camera to obtain an initial image. The purpose of collecting the initial image is to use the initial image as a basis for parameter adjustment, and to adjust the imaging parameters through the imaging effect of the wafer to be measured presented by the initial image, so as to improve the imaging effect of the wafer to be measured.

[0058] Step S120, determining whether the grayscale information of the overlay mark area in the initial image meets a preset condition. If the determination result is no, executing step S130; if the determination result is yes, performing overlay measurement on the wafer to be measured based on the initial imaging parameters.

[0059] Grayscale recognition processing is performed on the area where the overlay mark in the initial image is located to obtain grayscale information of the area where the overlay mark is located. The grayscale information is used to characterize the brightness of different pixels in the area where the overlay mark is located, and can quantify the brightness of each pixel in the image. Optionally, the grayscale information of the embodiment of the present application may be grayscale, grayscale value, etc., wherein grayscale generally refers to the brightness level in the image, that is, the grayscale value in a black and white image, and different grayscale values ​​correspond to different brightness. Optionally, the brightness of the image can also be represented by grayscale levels. For example, the grayscale is divided into multiple levels, such as 15 levels or 7 levels, etc. The larger the number of levels corresponding to the grayscale, the higher the brightness of the image. Optionally, the brightness of the overlay mark in the initial image can also be presented in the form of a brightness histogram, average brightness, etc.

[0060] It is understandable that the purpose of this application is to ensure that the overlay mark to be tested in the image is not too bright or too dark. Based on this, it is necessary to perform brightness recognition or grayscale recognition on the overlay mark. Optionally, grayscale recognition is performed on the entire initial image to obtain the grayscale value of each location, thereby determining the grayscale information corresponding to the overlay mark area of ​​the initial image.

[0061] In one possible implementation, a grayscale recognition process is performed on the overlay mark area in the initial image to obtain the grayscale of the overlay mark area as the grayscale information of the overlay mark area, including: identifying the inner area and the outer area of ​​the overlay mark area in the initial image; dividing the inner area and the outer area into a preset number of ROI areas respectively; performing grayscale recognition on each ROI area respectively to obtain the ROI grayscale of each ROI area; and determining the average value of the ROI grayscales corresponding to all ROI areas as the grayscale of the overlay mark area in the initial image.

[0062] Reference Figure 2, an example diagram of a grayscale recognition ROI area provided in an embodiment of the present application, wherein the overlay mark includes an inner region and an outer region. Optionally, the entire inner region and the outer region are regarded as a whole for grayscale recognition. However, due to differences in the structure of each area of ​​the overlay mark and the influence of external factors such as the light source, there are differences in the brightness / grayscale of different areas of an overlay mark, and the grayscale value obtained by the overall recognition may not accurately reflect the actual brightness state of the overlay mark.

[0063] In an embodiment of the present application, the overlay mark is divided into multiple ROI areas, wherein the ROI area (Region of Interest) needs to include at least the inner area or the outer area of ​​the overlay mark, and the shape, size, quantity, etc. of the area can be determined according to the shape and size of the overlay mark.

[0064] Reference Figure 2 The shapes of the outer and inner regions of the overlay mark are both rectangular, so the shape of the ROI region can also be set to a rectangle, and the size and number of each ROI region can be customized so that multiple ROI regions can basically cover the entire overlay mark, such as Figure 2 , set four ROI rectangular regions for the outer and inner regions of the overlay mark. Figure 3 , another example diagram of grayscale identification ROI area provided in an embodiment of the present application can also determine multiple ROI areas by scaling a graphic with the same shape as the inner layer area and the outer layer area, such as Figure 3 , wherein each ROI area has the same shape as the overlay mark but a different proportion. It can be seen that the shape, number, size, etc. of the ROI area can be set in various forms, and this application does not make a unique limitation.

[0065] Further, the grayscale value of each ROI region is identified, and the average brightness of the overlay mark is represented based on the average grayscale value of all ROI regions corresponding to the inner and outer regions of the overlay mark. Specifically, the grayscale of the overlay mark can be calculated by referring to the following formula (1).

[0066] (1)

[0067] Among them, G 0 represents the grayscale of the overlay mark area in the initial image, n represents the total number of ROI areas in the overlay mark, G i Represents the grayscale of the i-th ROI area.

[0068] Furthermore, the grayscale information of the overlay mark area in the initial image is compared with the preset conditions, such as comparing the grayscale of the overlay mark area with the preset grayscale threshold, to determine whether the image of the wafer to be tested acquired based on the initial imaging parameters meets the brightness requirements. Among them, the preset conditions and the preset grayscale threshold can be set by the equipment developer or tester according to the measurement requirements. Generally, when the overlay measurement accuracy is required, the image of the wafer to be tested cannot be too bright or too dark, which affects the clarity of the image. Therefore, the preset threshold can usually be set at an intermediate value between the two conditions of being too bright and too dark. In addition, in order to ensure that each overlay mark in the wafer to be tested is clearly imaged and the brightness is consistent, the preset grayscale threshold corresponding to each overlay mark should be the same threshold.

[0069] If the grayscale of the overlay mark area in the initial image is within the range specified by the preset grayscale threshold, it is determined that the grayscale information of the overlay mark area in the initial image meets the preset conditions, indicating that in the initial image corresponding to the initial imaging parameters, the brightness of the overlay mark meets the requirements and can be clearly imaged. There is no need to adjust the imaging parameters. According to the initial imaging parameters, the camera is controlled to capture the image of the overlay mark and perform overlay measurement.

[0070] However, if the grayscale of the overlay mark area in the initial image is not within the range specified by the preset grayscale threshold, it is determined that the grayscale information of the overlay mark area in the initial image does not meet the preset conditions, indicating that the initial image corresponding to the initial imaging parameters cannot meet the requirements of consistent brightness and clear imaging of the overlay mark, and it is necessary to further execute step S130 to adjust the imaging parameters.

[0071] Step S130, adjusting the initial camera exposure time to a first camera exposure time according to the corresponding relationship between the camera exposure time and the grayscale information.

[0072] Among them, the correspondence between the camera exposure time and the grayscale information can be: a correspondence determined by the inverse relationship between the adjustment amount of the initial camera exposure time and the grayscale information of the overlay mark area in the initial image, or a correspondence determined by the inverse relationship between the camera exposure time that makes the grayscale information of the overlay mark area after adjustment meet the preset conditions and the grayscale information of the overlay mark area in the initial image.

[0073] It is understandable that the exposure time of the camera, also known as the shutter speed, refers to the time that the light stays on the image sensor during the shooting process. The longer the exposure time, the shorter the light received by the image sensor, which makes the collected image of the overlay mark brighter, and the grayscale value / grayscale response of the overlay mark increases. On the contrary, if the exposure time is too short, the amount of light received by the image sensor is insufficient, and the collected image of the overlay mark is too dark, then the grayscale value / grayscale response of the overlay mark is low. Therefore, when the image of the overlay mark is too bright or too dark, the pattern details of the overlay mark may be overexposed or insufficient in light, resulting in unclear imaging, which may cause loss of pattern details or distortion of the pattern, and directly affect the result of the overlay measurement.

[0074] Based on this, if the grayscale information of the overlay mark area in the current initial image does not meet the preset conditions and the grayscale value is too large, the image is too bright and the initial camera exposure time is long, so the camera exposure time should be adjusted down. If the grayscale information of the overlay mark area in the current initial image does not meet the preset grayscale threshold conditions and the grayscale value is too small, the image is too dark and the initial camera exposure time is short, so the camera exposure time should be adjusted up. It can be seen that the adjusted camera exposure time is inversely proportional to the grayscale information of the overlay mark area in the initial image.

[0075] Further, the inverse relationship is precisely determined to determine the relationship between the grayscale information of the overlay mark area in the initial image and the adjustment amount of the camera exposure time, or to determine the relationship between the grayscale information of the overlay mark area in the initial image and the adjusted camera exposure time. In a possible implementation, a pre-set exposure time adjustment relationship formula that characterizes the corresponding relationship between the camera exposure time and the grayscale information is called, and the exposure time adjustment relationship formula is an expression of the camera exposure time with respect to the grayscale information of the overlay mark area, wherein the camera exposure time is equal to the quotient of the exposure parameter and the grayscale information of the overlay mark area, and the exposure parameter is the product of the preset grayscale information limit value and the initial camera exposure time; according to the exposure time adjustment relationship formula, a first camera exposure time corresponding to the grayscale information of the overlay mark area is determined; and the initial camera exposure time is adjusted to the first camera exposure time.

[0076] An exposure time adjustment equation representing the relationship between the grayscale of the overlay mark area in the current initial image and the adjusted camera exposure time is pre-fitted, referring to the following equation (2). Based on the exposure time adjustment equation, the adjusted first camera exposure time corresponding to the grayscale of the overlay mark area is determined.

[0077] (2)

[0078] Among them, T 2 Indicates the exposure time of the first camera, T 1represents the initial camera exposure time, G 0 represents the grayscale of the overlay mark area in the initial image, G max Indicates the preset grayscale upper limit, G min represents a preset grayscale lower limit value, wherein the grayscale upper limit value and the grayscale lower limit value are grayscale range values ​​defined in the preset grayscale threshold condition.

[0079] In another possible implementation, the relationship between the grayscale information of the overlay mark area and the camera exposure is determined, so as to further determine the first camera exposure time for adjusting the grayscale information of the overlay mark area to meet the preset conditions. Optionally, for the overlay mark, a plurality of different camera exposure times are set, and the imaging overlay measurement device is controlled to capture the image of the overlay mark with different camera exposure times, and the grayscale value or grayscale value of each image is identified, and each camera exposure time and the grayscale value corresponding to each camera exposure time are fitted to obtain the functional relationship between the camera exposure time and the grayscale. Based on the functional relationship, the camera exposure time corresponding to the grayscale value that meets the preset grayscale threshold condition is determined, and this is used as the first camera exposure time.

[0080] Step S140, determining whether the exposure time of the first camera meets the exposure condition. If the determination result is yes, executing step S150; if the determination result is no, executing step S160.

[0081] Step S150, using the first camera exposure time and the initial light source attenuation sheet position as imaging parameters, and controlling the camera to perform an acquisition operation.

[0082] It is understandable that camera exposure time is related to camera hardware performance, exposure mode, ISO value, lighting conditions, camera stability, and battery life. Therefore, camera exposure time is subject to exposure conditions and needs to be adjusted within a certain range and cannot be adjusted up or down indefinitely.

[0083] Based on this, the exposure condition is: the exposure time of the first camera is within the preset exposure time threshold range, and the preset exposure time threshold range is determined according to the exposure time range allowed by the hardware structure of the camera. The camera exposure time range allowed by the camera is determined in advance according to the imaging device in the imaging overlay measurement device, that is, the hardware performance of the camera, as the preset exposure time threshold.

[0084] Furthermore, the first camera exposure time is compared with the camera exposure time range. If the first camera exposure time exceeds the exposure time range that the camera can achieve, the first exposure time cannot be achieved, and it is necessary to adjust the brightness by adjusting other parameters in the imaging parameters, that is, to execute step S160. If the first camera exposure time is within the exposure time range that the camera can achieve, step S150 can be executed, using the first camera exposure time and the initial light source attenuation sheet gear as imaging parameters to perform image acquisition and overlay measurement on the overlay mark.

[0085] Step S160: adjusting the initial light source attenuation sheet position to the first light source attenuation sheet position according to the corresponding relationship between the light source attenuation sheet position and the grayscale information.

[0086] Step S170: Using the initial camera exposure time and the first light source attenuation plate position as imaging parameters, the camera is controlled to perform an acquisition operation.

[0087] Light source attenuation sheets, also known as neutral density filters, have the main function of reducing light intensity by absorbing, scattering or reflecting light. The material, design wavelength, thickness, etc. of the light source attenuation sheet will affect the light attenuation of the light source attenuation sheet. Usually, in order to meet various measurement requirements, imaging overlay measurement equipment will set up light source attenuation sheets with multiple gears. Among them, light source attenuation sheets with different gears have different attenuation amounts, that is, they have different degrees of attenuation of light. Figure 4 , a schematic diagram of a light source attenuation sheet provided in an embodiment of the present application, the light source attenuation mechanism of the imaging overlay device is usually an attenuation sheet turntable, which includes a plurality of light source attenuation sheets with different gears, and different light source attenuations can be achieved by switching light source attenuation sheets with different attenuation coefficients into the optical path.

[0088] In the embodiment of the present application, the lower the gear of the light source attenuation plate, the greater its attenuation, and the more obvious the light attenuation effect. Based on this, if the grayscale of the overlay mark area in the current initial image does not meet the preset grayscale threshold condition, and the grayscale is too large, there is a problem of the image being too bright, so it is necessary to appropriately lower the gear of the light source attenuation plate to enhance the light attenuation effect, so that the brightness of the overlay image collected after the gear is adjusted is reduced. On the contrary, if the grayscale of the overlay mark area in the current initial image does not meet the preset grayscale threshold condition, and the grayscale is too small, there is a problem of the image being too dark, so it is necessary to appropriately increase the gear of the light source attenuation plate to reduce the light attenuation effect, so that the brightness of the overlay image collected after the gear is adjusted is enhanced. Based on this, the adjusted gear of the light source attenuation plate is inversely proportional to the grayscale.

[0089] Furthermore, based on the inverse relationship between the light source attenuation plate position that makes the grayscale information of the overlay mark area after adjustment meet the preset conditions and the grayscale information of the overlay mark area in the initial image, the corresponding relationship between the light source attenuation plate position and the grayscale information is determined, or the relationship between the grayscale and the adjustment amount of the light source attenuation plate position is determined.

[0090] In a possible implementation, the process of adjusting the initial light source attenuation plate gear position to the first light source attenuation plate gear position according to the correspondence between the light source attenuation plate gear position and the grayscale information includes: calling a preset light source attenuation plate gear position adjustment relationship formula that characterizes the correspondence between the light source attenuation plate gear position and the grayscale information, the light source attenuation plate gear position adjustment relationship formula being an expression of the light source attenuation plate gear position with respect to the grayscale information of the overlay mark area, wherein the light source attenuation plate gear position is equal to the quotient of the attenuation plate gear position parameter and the grayscale information of the overlay mark area, and the attenuation plate gear position parameter is the quotient of the preset grayscale information limit value and the initial light source attenuation plate gear position; determining the pending light source attenuation plate gear position corresponding to the grayscale information of the overlay mark area according to the light source attenuation plate gear position adjustment relationship formula; obtaining a gear list of the light source attenuation plate gear positions; and determining, from the gear list, the light source attenuation plate gear position that is closest to the pending light source attenuation plate gear position as the first light source attenuation plate gear position.

[0091] The exposure time adjustment relationship that characterizes the relationship between the grayscale of the current overlay mark area and the adjusted light source attenuation plate position is pre-fitted, referring to the following formula (3). According to the light source attenuation plate position adjustment relationship, the grayscale information of the overlay mark area in the initial image is determined, that is, the adjusted light source attenuation plate position corresponding to the grayscale, that is, the undetermined light source attenuation plate position.

[0092] (3)

[0093] Among them, L 2 Indicates the undetermined light source attenuation position, L 1 Indicates the initial light source attenuation position, G max Indicates the preset grayscale upper limit, G min Indicates the preset grayscale lower limit.

[0094] Further, a gear list of light source attenuation plate gears is obtained; from the gear list, a light source attenuation plate gear that is closest to the to-be-determined light source attenuation plate gear is determined as the first light source attenuation plate gear.

[0095] It can be understood that the undetermined light source attenuation sheet level L2 obtained by formula (3) is in fractional form, while the actual light source attenuation sheet levels are all integers. Therefore, the actual level closest to L2 in the level list can be selected as the first light source attenuation sheet level.

[0096] Since the first camera exposure time no longer meets the camera performance, the initial camera exposure time and the first light source attenuation plate position are used as the camera imaging parameters to collect the image of the overlay mark and perform the next overlay measurement.

[0097] In summary, the overlay measurement imaging brightness adjustment method provided in the embodiment of the present application, when it is detected that the overlay mark image captured by the current initial imaging parameters has an image intensity that does not meet the preset requirements, the camera exposure time is preferentially adjusted according to the inverse relationship between the grayscale and the camera exposure time, and the brightness of the image captured again subsequently is adjusted. However, considering that the camera has a limitation on exposure time due to its own hardware limitations, if the exposure time of the first camera is not within the limitation range, the brightness of the image captured again subsequently is adjusted by adjusting the gear position of the light source attenuation plate.

[0098] Based on this, compared with the prior art of capturing the image of each overlay mark with fixed camera parameters, the present application can adjust parameters for each overlay mark in the wafer to be measured when performing overlay measurement, ensuring that the brightness of each overlay mark image meets the requirements, and performing overlay measurement based on the overlay mark image that meets the brightness requirements, thereby further improving the accuracy of the measurement of each overlay mark.

[0099] The overlay measurement imaging brightness adjustment device provided in an embodiment of the present application is described below. The overlay measurement imaging brightness adjustment device described below and the overlay measurement imaging brightness adjustment method described above can refer to each other.

[0100] First, combine Figure 5 , an overlay measurement imaging brightness adjustment device for a controller of an imaging overlay measurement device is introduced, such as Figure 5 As shown, the overlay measurement imaging brightness adjustment device may include:

[0101] The initial image acquisition unit 100 is used to acquire an initial image of the wafer to be measured, wherein the initial image is acquired by controlling the camera of the overlay measurement device according to the preset initial imaging parameters, wherein the initial image includes the overlay mark area where the overlay mark is located, and the initial imaging parameters at least include: initial camera exposure time and initial light source attenuation profile;

[0102] An exposure time adjustment unit 200 is used to adjust the initial camera exposure time to a first camera exposure time according to a correspondence between camera exposure time and grayscale information when the grayscale information of the overlay mark area does not meet a preset condition;

[0103] The control acquisition unit 300 is used to control the camera to perform an acquisition operation by taking the exposure time of the first camera and the initial light source attenuation sheet position as imaging parameters when the exposure time of the first camera meets the exposure condition.

[0104] In a possible implementation, when the exposure time of the first camera does not meet the exposure condition, the overlay measurement imaging brightness adjustment device further includes:

[0105] An attenuation sheet position adjustment unit, configured to adjust the initial light source attenuation sheet position to a first light source attenuation sheet position according to a corresponding relationship between the light source attenuation sheet position and grayscale information;

[0106] An acquisition control unit is used to control the camera to perform an acquisition operation by taking the initial camera exposure time and the first light source attenuation sheet position as imaging parameters.

[0107] In a possible implementation, the exposure condition is: the exposure time of the first camera is within a preset exposure time threshold range, and the preset exposure time threshold range is determined according to an exposure time range allowed by the hardware structure of the camera.

[0108] In one possible implementation, the correspondence between the camera exposure time and the grayscale information is a correspondence determined by the inverse relationship between the camera exposure time that makes the grayscale information of the overlay mark area after the adjustment meet the preset conditions and the grayscale information of the overlay mark area in the initial image, and the grayscale information is used to characterize the brightness of different pixel points in the area where the overlay mark is located.

[0109] In a possible implementation, the correspondence between the light source attenuation plate gear position and the grayscale information is a correspondence determined by the inverse relationship between the light source attenuation plate gear position that makes the grayscale information of the overlay mark area after adjustment meet preset conditions and the grayscale information of the overlay mark area in the initial image.

[0110] In a possible implementation, the exposure time adjustment unit 200 includes:

[0111] A relational expression calling subunit is used to call a preset exposure time adjustment relational expression that characterizes the corresponding relationship between camera exposure time and grayscale information, wherein the exposure time adjustment relational expression is an expression of the camera exposure time with respect to the grayscale information of the overlay mark area, wherein the camera exposure time is equal to a quotient of an exposure parameter and the grayscale information of the overlay mark area, and the exposure parameter is the product of a preset grayscale information limit value and the initial camera exposure time;

[0112] A first exposure time determination subunit, configured to determine a first camera exposure time corresponding to the grayscale information of the overlay mark area according to the exposure time adjustment relationship;

[0113] The time adjustment subunit is used to adjust the initial camera exposure time to the first camera exposure time.

[0114] In a possible implementation, the attenuation sheet gear position adjustment unit includes:

[0115] A gear adjustment relational formula calling subunit is used to call a preset light source attenuation sheet gear adjustment relational formula that characterizes the corresponding relationship between the light source attenuation sheet gear and the grayscale information, wherein the light source attenuation sheet gear adjustment relational formula is an expression of the light source attenuation sheet gear with respect to the grayscale information of the overlay mark area, wherein the light source attenuation sheet gear is equal to the quotient of the attenuation sheet gear parameter and the grayscale information of the overlay mark area, and the attenuation sheet gear parameter is the quotient of a preset grayscale information limit value and the initial light source attenuation sheet gear;

[0116] A to-be-determined gear position determination subunit, used to determine the first light source attenuation plate gear position corresponding to the grayscale information of the overlay mark area according to the light source attenuation plate gear position adjustment relationship;

[0117] A list acquisition subunit is used to acquire a gear list of the light source attenuation sheet gears;

[0118] The gear position determination subunit is used to determine, from the gear position list, a light source attenuation plate gear position that is closest to the to-be-determined light source attenuation plate gear position as the first light source attenuation plate gear position.

[0119] In a possible implementation, the functional unit for detecting the grayscale information of the overlay mark area in the initial image captured by the camera according to the preset initial imaging parameters includes:

[0120] The grayscale recognition unit is used to perform grayscale recognition processing on the overlay mark area in the initial image to obtain the grayscale of the overlay mark area as the grayscale information of the overlay mark area.

[0121] In a possible implementation, the grayscale recognition unit includes:

[0122] A region identification subunit, used for identifying an inner region and an outer region of the overlay mark region in the initial image;

[0123] The ROI region division subunit is used to divide the inner region and the outer region into a preset number of ROI regions respectively;

[0124] A regional grayscale identification subunit, used for performing grayscale identification on each of the ROI regions to obtain the ROI grayscale of each of the ROI regions;

[0125] The grayscale determination subunit is used to determine the average value of the ROI grayscales corresponding to all the ROI regions as the grayscale of the region where the overlay mark is located in the initial image.

[0126] In summary, the embodiment of the present application provides that when the image intensity of the overlay mark image captured by the current initial imaging parameters does not meet the preset requirements, the camera exposure time is preferentially adjusted according to the inverse relationship between the grayscale and the camera exposure time, and the brightness of the image captured again subsequently is adjusted. However, considering that the camera has a limitation on the exposure time due to its own hardware limitations, if the exposure time of the first camera is not within the limitation range, the brightness of the image captured again subsequently is adjusted by adjusting the gear position of the light source attenuation plate.

[0127] Based on this, compared with the prior art of capturing the image of each overlay mark with fixed camera parameters, the present application can adjust parameters for each overlay mark in the wafer to be measured when performing overlay measurement, ensuring that the brightness of each overlay mark image meets the requirements, and performing overlay measurement based on the overlay mark image that meets the brightness requirements, thereby further improving the accuracy of the measurement of each overlay mark.

[0128] The overlay measurement imaging brightness adjustment device provided in the embodiment of the present application can be applied to overlay measurement imaging brightness adjustment equipment.

[0129] Figure 6 The schematic diagram of the structure of the overlay measurement imaging brightness adjustment device is shown. Figure 6 The structure of the overlay measurement imaging brightness adjustment device may include: at least one processor 10, at least one memory 20, at least one communication bus 30 and at least one communication interface 40.

[0130] In the embodiment of the present application, the number of the processor 10 , the memory 20 , the communication bus 30 , and the communication interface 40 is at least one, and the processor 10 , the memory 20 , and the communication interface 40 communicate with each other through the communication bus 30 .

[0131] The processor 10 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0132] The memory 20 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), etc., such as at least one disk memory.

[0133] The memory stores a program, and the processor can call the program stored in the memory, and the program is used to implement each processing flow in the above-mentioned overlay measurement imaging brightness adjustment method.

[0134] A computer storage medium is also provided in an embodiment of the present application. The storage medium carries one or more computer programs. When the one or more computer programs are executed by the overlay measurement imaging brightness adjustment device, the overlay measurement imaging brightness adjustment device can implement any one of the overlay measurement imaging brightness adjustment methods provided in the embodiments of the present application.

[0135] The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website site, a computer, a training device, or a data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, training device, or data center. The computer-readable storage medium may be any available medium that a computer can store or a data storage device such as a training device, a data center, etc. that includes one or more available media integrations. The available medium may be a magnetic medium, (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)), etc.

[0136] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants 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. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0137] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0138] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for adjusting the brightness of overlay measurement imaging, characterized in that: include: Acquire an initial image of the wafer to be measured, wherein the initial image is acquired by controlling a camera of an overlay measurement device according to pre-set initial imaging parameters, wherein the initial image includes an overlay mark area where an overlay mark is located, and the initial imaging parameters at least include: an initial camera exposure time and an initial light source attenuation profile; When the grayscale information of the overlay mark area does not meet the preset condition, adjusting the initial camera exposure time to the first camera exposure time according to the corresponding relationship between the camera exposure time and the grayscale information; When the exposure time of the first camera meets the exposure condition, the exposure time of the first camera and the initial light source attenuation plate position are used as imaging parameters to control the camera to perform an acquisition operation.

2. The overlay measurement imaging brightness adjustment method according to claim 1, characterized in that: When the exposure time of the first camera does not meet the exposure condition, the overlay measurement imaging brightness adjustment method further includes: According to the corresponding relationship between the light source attenuation sheet position and the grayscale information, the initial light source attenuation sheet position is adjusted to the first light source attenuation sheet position; The initial camera exposure time and the first light source attenuation plate position are used as imaging parameters to control the camera to perform an acquisition operation.

3. The overlay measurement imaging brightness adjustment method according to claim 1, characterized in that: The exposure condition is: the exposure time of the first camera is within a preset exposure time threshold range, and the preset exposure time threshold range is determined according to the exposure time range allowed by the hardware structure of the camera.

4. The overlay measurement imaging brightness adjustment method according to claim 1, characterized in that: The correspondence between the camera exposure time and the grayscale information is a correspondence determined by the inverse relationship between the camera exposure time that makes the grayscale information of the overlay mark area after adjustment meet the preset conditions and the grayscale information of the overlay mark area in the initial image, and the grayscale information is used to characterize the brightness of different pixels in the overlay mark area.

5. The overlay measurement imaging brightness adjustment method according to claim 2, characterized in that: The correspondence between the light source attenuation plate gear position and the grayscale information is determined by the inverse relationship between the light source attenuation plate gear position that makes the grayscale information of the overlay mark area after adjustment meet the preset conditions and the grayscale information of the overlay mark area in the initial image.

6. The overlay measurement imaging brightness adjustment method according to claim 1, characterized in that: The adjusting the initial camera exposure time to the first camera exposure time according to the correspondence between the camera exposure time and the grayscale information includes: Calling a preset exposure time adjustment relational expression characterizing the correspondence between camera exposure time and grayscale information, wherein the exposure time adjustment relational expression is an expression of the camera exposure time with respect to the grayscale information of the overlay mark area, wherein the camera exposure time is equal to a quotient of an exposure parameter and the grayscale information of the overlay mark area, and the exposure parameter is the product of a preset grayscale information limit value and the initial camera exposure time; Determining a first camera exposure time corresponding to the grayscale information of the overlay mark area according to the exposure time adjustment relationship; The initial camera exposure time is adjusted to the first camera exposure time.

7. The overlay measurement imaging brightness adjustment method according to claim 2, characterized in that: The adjusting the initial light source attenuation sheet position to the first light source attenuation sheet position according to the correspondence between the light source attenuation sheet position and the grayscale information comprises: Calling a preset light source attenuation sheet position adjustment relational expression that characterizes the correspondence between the light source attenuation sheet position and the grayscale information, wherein the light source attenuation sheet position adjustment relational expression is an expression of the light source attenuation sheet position with respect to the grayscale information of the overlay mark area, wherein the light source attenuation sheet position is equal to the quotient of the attenuation sheet position parameter and the grayscale information of the overlay mark area, and the attenuation sheet position parameter is the quotient of a preset grayscale information limit value and the initial light source attenuation sheet position; Determine the undetermined light source attenuation plate gear position corresponding to the grayscale information of the overlay mark area according to the light source attenuation plate gear position adjustment relationship; Get the gear list of the light source attenuation sheet gear; From the gear list, a light source attenuation plate gear that is closest to the undetermined light source attenuation plate gear is determined as the first light source attenuation plate gear.

8. The overlay measurement imaging brightness adjustment method according to any one of claims 1 to 7, characterized in that: The process of detecting the grayscale information of the overlay mark area in the initial image captured by the camera according to the preset initial imaging parameters includes: Grayscale recognition processing is performed on the overlay mark area in the initial image to obtain the grayscale of the overlay mark area as grayscale information of the overlay mark area.

9. The overlay measurement imaging brightness adjustment method according to claim 8, characterized in that: The performing grayscale recognition processing on the overlay mark area in the initial image to obtain the grayscale of the overlay mark area includes: Identifying an inner region and an outer region of the overlay mark region in the initial image; Dividing the inner layer area and the outer layer area into a preset number of ROI areas respectively; Performing grayscale recognition on each of the ROI regions respectively to obtain the ROI grayscale of each of the ROI regions; The average value of the ROI grayscales corresponding to all the ROI regions is determined as the grayscale of the region where the overlay mark is located in the initial image.

10. An overlay measurement imaging brightness adjustment device, characterized in that: include: An initial image acquisition unit is used to acquire an initial image of the wafer to be measured, wherein the initial image is acquired by controlling the camera of the overlay measurement device according to preset initial imaging parameters, wherein the initial image includes an overlay mark area where the overlay mark is located, and the initial imaging parameters at least include: initial camera exposure time and initial light source attenuation profile; an exposure time adjustment unit, configured to adjust the initial camera exposure time to a first camera exposure time according to a correspondence between camera exposure time and grayscale information when the grayscale information of the overlay mark area does not meet a preset condition; The control acquisition unit is used to control the camera to perform an acquisition operation by taking the exposure time of the first camera and the initial light source attenuation sheet position as imaging parameters when the exposure time of the first camera meets the exposure condition.

11. An overlay measurement imaging brightness adjustment device, characterized in that: The method comprises at least one processor and a memory connected to the processor, wherein: The memory is used to store computer programs; The processor is used to execute the computer program so that the overlay measurement imaging brightness adjustment device can implement the overlay measurement imaging brightness adjustment method as described in any one of claims 1 to 9.

12. A computer storage medium, characterized in that: The storage medium carries one or more computer programs. When the one or more computer programs are executed by the overlay measurement imaging brightness adjustment device, the overlay measurement imaging brightness adjustment device can implement the overlay measurement imaging brightness adjustment method as described in any one of claims 1 to 9.

13. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, each step of the overlay measurement imaging brightness adjustment method according to any one of claims 1 to 9 is implemented.

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