Method, device and storage medium for positioning wafer measurement area

Abstract

The present application discloses a method, device and storage medium for positioning a wafer measurement area. The method comprises: collecting a measurement image and a reference image of a measurement area in a wafer; constructing a flatness template image related to the measurement area based on the measurement image; and matching the flatness template image with the reference image to obtain a matching result; and positioning the measurement area according to the matching result. By using the solution of the present application, accurate positioning of the measurement area in a wafer can be achieved.

Description

Technical Field

[0001] The present application generally relates to the field of wafer measurement technology. More specifically, the present application relates to a method, device and computer-readable storage medium for locating a wafer measurement area. Background Art

[0002] The measurement based on the unidirectional periodic SEM image is often assisted by the addressing pattern ("Addressing pattern") of the auxiliary positioning image (or reference image). Specifically, the position of the positioning image is first found through pattern matching ("pattern match"), and then the measurement position of the measurement area is determined by the deflection of the electron beam in the SEM according to the relative position relationship between the set measurement image and the positioning image.

[0003] It can be understood that after the aforementioned addressing mode positioning, in order to make the scanning electron microscope field of view reach the specified measurement position, the electron beam needs to be deflected. Mainly by controlling the deflector of the scanning electron microscope, the electron beam position is deflected to make it reach the measurement area. This process is a conventional measurement area positioning process, and there may be positioning deviations in the horizontal direction (for example, the X direction) or the vertical direction (for example, the Y direction). In pattern matching, the aforementioned positioning deviation problem can be solved by, for example, a zero mean normalized cross-correlation (Zero Mean Normalized Cross-Correlation, "ZNCC") algorithm. However, the method of pattern matching after the addressing mode auxiliary positioning is suitable for scenes with large image differences. For situations where the image texture, grayscale distribution characteristics, and edge characteristics in the measurement area are very close, it is difficult to achieve the purpose of accurate positioning only by the method of pattern matching after the addressing mode auxiliary positioning, which results in the subsequent inability to accurately locate the measurement position.

[0004] In view of this, there is an urgent need to provide a solution for positioning the measurement area of ​​the wafer, so as to accurately position the measurement area in the wafer. Summary of the invention

[0005] In order to at least solve one or more of the technical problems mentioned above, the present application proposes solutions for positioning a wafer measurement area in multiple aspects.

[0006] In a first aspect, the present application provides a method for locating a measurement area of ​​a wafer, comprising: acquiring a measurement image and a reference image of a measurement area in a wafer; constructing a flatness template image related to the measurement area based on the measurement image; and matching the flatness template image with the reference image to obtain a matching result; and locating the measurement area according to the matching result.

[0007] In one embodiment, the measurement image and the reference image are acquired along the longitudinal direction of the measurement area.

[0008] In another embodiment, constructing a flatness template image related to the measurement area based on the measurement image includes: performing a background removal operation on the measurement image; and performing a signal strength analysis on the measurement image after background removal to construct a flatness template image related to the measurement area.

[0009] In yet another embodiment, performing a background removal operation on the measurement image includes: using a ball to roll and scan each pixel point in the measurement image row by row, and removing the pixel points that the ball can touch, so as to perform a background removal operation on the measurement image.

[0010] In yet another embodiment, performing signal strength analysis on the measurement image after background removal to construct a flatness template image related to the measurement area includes: calculating the pixel mean along the longitudinal direction of the pixel points in the measurement image after background removal to construct the flatness template image related to the measurement area.

[0011] In yet another embodiment, before performing a background removal operation on the measurement image, it further includes: determining whether the background of the measurement image is a black feature; and in response to the background of the measurement image not being the black feature, performing a pixel inversion operation on image pixels in the measurement image.

[0012] In another embodiment, matching the flatness template image with the reference image to obtain a matching result includes: calculating a median error function between the flatness template image and the reference image; and determining a minimum value of the median error function to obtain the matching result.

[0013] In another embodiment, calculating the median error function between the flatness template image and the reference image includes: calculating the median of the reference image; and calculating the median error function between the flatness template image and the reference image based on the absolute value of the difference between each pixel in the flatness template image and the median.

[0014] In a second aspect, the present application provides a device for positioning a wafer measurement area, comprising: a processor; and a memory on which computer instructions for positioning a wafer measurement area are stored, and when the computer instructions are executed by the processor, multiple embodiments of the aforementioned first aspect are implemented.

[0015] In a third aspect, the present application provides a computer-readable storage medium having stored thereon computer program instructions for positioning a wafer measurement area, wherein when the computer program instructions are executed by one or more processors, multiple embodiments of the aforementioned first aspect are implemented.

[0016] Through the solution for positioning the wafer measurement area as provided above, the embodiment of the present application first constructs a flatness template image of the relevant measurement area based on the measurement image, and the flatness template image has a relatively different flatness feature. Then, the flatness template image is matched with the reference image, that is, the reference image is matched by the differentiated features, which can improve the accuracy of positioning the measurement area so as to accurately locate the measurement position later. Furthermore, the embodiment of the present application determines the matching result by the minimum value of the median error function, which can fully consider the matching accuracy of each area, and is particularly suitable for matching processes with obvious differences in pattern features, thereby improving matching accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present application will become easy to understand. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0018] Figure 1 is an exemplary schematic diagram showing periodic image measurement in the X direction;

[0019] Figure 2 is an exemplary flowchart showing a method for locating a wafer measurement area according to an embodiment of the present application;

[0020] Figure 3 is an exemplary framework diagram showing positioning of a wafer measurement area according to an embodiment of the present application;

[0021] Figure 4 is an exemplary flowchart showing the construction of a flatness template image according to an embodiment of the present application;

[0022] Figure 5 is an exemplary flow chart showing the overall positioning of the wafer measurement area according to an embodiment of the present application;

[0023] Figure 6 It is an exemplary structural block diagram of a device for positioning a wafer measurement area according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] 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 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 those skilled in the art without creative work are within the scope of protection of the present application.

[0025] It should be understood that the terms "include" and "comprising" used in the specification and claims of the present application indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0026] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this application specification and claims, unless the context clearly indicates otherwise, the singular forms of "a", "an" and "the" are intended to include plural forms. It should also be further understood that the term "and / or" used in this application specification and claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0027] As used in this specification and claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0028] Figure 1 FIG. 1 is an exemplary schematic diagram showing periodic image measurement in the X direction. Figure 1 FIG. 10( a ) shows, by way of example, the upper and lower overlapping regions of the white box A and the white box B, wherein the white box A represents the measurement region that actually needs to be positioned, and the white box B represents the region positioned by the addressing mode (e.g. Figure 1 After the electron beam is deflected and automatically focused on the measurement area, there is a positioning deviation in the Y direction. It can be understood that addressing and positioning is achieved by pattern recognition, using a special pattern that can be easily recognized by the image processing algorithm as an addressing reference image, and then using the pattern matching method to match the scanning electron microscope image collected by the scanning electron microscope with the reference image, and the image area with the greatest correlation in the matching result is used as the addressing and positioning result. For example Figure 1The right side of Figure (b) contains a rich pattern, with square holes and horizontal stripes of different sizes as reference patterns, which can be used as an addressing reference image.

[0029] In pattern matching, the area shown in the white box B needs to be matched to the area shown in the white box A. For the positioning deviation in the Y direction, since the surrounding features of the measurement type (such as line width type) are very similar, the measurement images of the upper and lower areas are very similar in grayscale, texture, and two-dimensional edge features. If only the ZNCC algorithm is used to achieve pattern matching, the matching accuracy will be poor, and the area to be measured (such as the area shown in the white box A) cannot be accurately positioned.

[0030] Based on this, the present application provides a solution for locating the wafer measurement area, by first constructing a flatness template image based on the measurement image, and then matching the flatness template image with the reference image. The flatness features on the flatness template image will have a large difference after photolithography, and by using this differentiated feature as a template for model matching, accurate positioning of the measurement area can be achieved.

[0031] The specific implementation of the present application is described in detail below with reference to the accompanying drawings.

[0032] Figure 2 FIG. 2 is an exemplary flowchart of a method 200 for locating a wafer measurement area according to an embodiment of the present application. Figure 2 As shown in, at step S201, a measurement image and a reference image of the measurement area in the wafer are collected. In some embodiments, the aforementioned measurement image and reference image can be obtained by, for example, collecting via a scanning electron microscope. In particular, the aforementioned measurement image and reference image are collected along the longitudinal direction (Y direction) of the measurement area. That is, the embodiment of the present application is used for positioning deviation in the Y direction. This is because there is a grayscale difference in the X direction, which can be positioned by pattern matching through, for example, a ZNCC algorithm, so that in the embodiment of the present application, it can be considered that the X direction has been positioned or there is no positioning deviation. In some implementation scenarios, in order to further improve the positioning accuracy, the embodiment of the present application can also be applied to the positioning deviation in the X direction, and the present application does not impose any restrictions on this.

[0033] Next, at step S202, a flatness template image of the relevant measurement area is constructed based on the measurement image. The construction of the flatness template image is to enhance the measurement image to remove the interference of background factors, and use the flatness feature image for subsequent matching to improve positioning accuracy.

[0034] In one embodiment, a background removal operation can be performed on the measurement image, and the signal strength analysis can be performed on the measurement image after the background is removed to construct a flatness template image of the relevant measurement area. In an implementation scenario, when performing a background removal operation on the measurement image, a ball can be used to roll and scan each pixel point in the measurement image line by line, and the pixel points that the ball can touch can be removed to perform a background removal operation on the measurement image. Specifically, a rolling ball algorithm can be used to perform a background removal operation. That is, each pixel point in the measurement image is scanned by a rolling ball line by line method, and all the relatively flat pixel points exposed outside the pixel depression are places that the ball can touch, and the pixel value can be cleared. For the pixel points that the ball cannot touch, some of the pixel points that the ball can touch are removed and then analyzed and counted, and the remaining pixel values ​​are averaged and analyzed and counted. Specifically, the pixel intensity of the remaining pixel points is analyzed, and different rolling ball diameters are used according to the different pixel intensities of the remaining pixel points. The statistical value after background subtraction is analyzed, and finally the rolling ball parameters that are optimal for removing the background are determined.

[0035] In one implementation scenario, the pixel average of the pixels in the measurement image after the background is removed can be calculated along the vertical direction to construct a flatness template image of the relevant measurement area. That is, the pixel values ​​of the remaining pixels are divided into columns, and the pixel values ​​of each column are averaged and analyzed and statistically analyzed to construct a flatness template image of the relevant measurement area.

[0036] In some implementation scenarios, before performing a background removal operation on the measurement image, it may also include determining whether the background of the measurement image is a black feature, and in response to the background of the measurement image not being a black feature, performing a pixel rotation operation on the image pixels in the measurement image. It can be understood that the aforementioned black feature is a pixel point with a pixel value of 0, and determining whether the background of the measurement image is a black feature is to determine whether the pixel value is 0. When the background of the measurement image is a black feature, the aforementioned background removal operation can be performed directly. When the background of the measurement image is not a black feature, a pixel rotation operation is first performed on the image pixels, and then the aforementioned background removal operation is directly performed. In some embodiments, the aforementioned pixel rotation operation can adopt, for example, a thresholding operation, usually setting a fixed threshold parameter or a dynamic threshold parameter, and converting part of the pixel values ​​whose background is not a black feature to a black background, so that an obvious brightness feature is presented in the area to be measured, which is convenient for subsequent more accurate matching.

[0037] Further, at step S203, the flatness template image is matched with the reference image to obtain a matching result. Specifically, in an implementation scenario, the median error function between the flatness template image and the reference image is first calculated, and the matching result is obtained by determining the minimum value of the median error function. In an implementation scenario, the median of the reference image is calculated, and the median error function between the flatness template image and the reference image is calculated based on the absolute value of the difference between each pixel in the flatness template image and the median. That is, the median error function is obtained by first determining the median of the pixel in the reference image, and then calculating the absolute value of the difference between each pixel in the flatness template image and the median. Among them, the position corresponding to the minimum value of the median error function is the matching point, that is, the matching result.

[0038] Finally, in step S204, the measurement area is positioned according to the matching result. In the implementation scenario, the flatness image is matched to the reference image by taking the position corresponding to the minimum value of the median error function as the matching point, so as to locate the measurement area and obtain an accurate measurement position.

[0039] Combined with the above description, it can be seen that the embodiment of the present application determines the matching result between the measurement image and the reference image by constructing a flatness template image of the measurement area based on the measurement image. Compared with directly using the original measurement image and reference image, the flatness template image enhanced by background removal has a relatively different flatness feature, which can more accurately locate the measurement area, so as to accurately locate the measurement position later, and help improve the reliability of short-term repeatability, and is also more conducive to the matching results between different measurement machines, and improves the overall performance indicators of the measurement machine.

[0040] Furthermore, the embodiment of the present application also determines the matching result by the minimum value of the median error function, which can further improve the matching accuracy. This is because the median error function uses each sample and the mean absolute value to sort in ascending order, and takes the middle value as the matching result, so that the matching accuracy of each area can be fully considered, and the matching accuracy can be improved, which is especially suitable for matching processes with obvious differences in pattern features.

[0041] Figure 3 is an exemplary framework diagram showing positioning of a wafer measurement area according to an embodiment of the present application. Figure 3As shown in , first, a reference image 301 and a measurement image 302 of a measurement area in a wafer are acquired by, for example, a scanning electron microscope. In particular, the reference image 301 and the measurement image 302 are acquired along the longitudinal direction (Y direction) of the measurement area. Next, a flatness template image 303 is constructed based on the measurement image 302. As can be seen from the foregoing, a background removal operation can be performed on the measurement image, and the signal intensity analysis can be performed on the measurement image after the background removal to construct a flatness template image of the relevant measurement area.

[0042] In some embodiments, a background removal operation can be performed by, for example, a rolling ball algorithm. Specifically, a ball is used to roll and scan each pixel point in the measurement image row by row, and the pixel points that the ball can touch are removed to perform a background removal operation on the measurement image. Furthermore, the pixel values ​​of the remaining pixels are divided into columns, and the pixels in each column are averaged and analyzed and statistically analyzed to construct a flatness template image of the relevant measurement area. In some embodiments, before performing a background removal operation on the measurement image, it is first determined whether the background in the measurement image is a black feature. If so, the background removal operation is performed directly. If not, a pixel rotation operation is performed first.

[0043] Based on the flatness template image 303 constructed above, the flatness template image 303 is matched 304 with the reference image 301 to determine a matching result, and then the measurement area is positioned by the matching result. In an implementation scenario, the matching can be achieved by calculating the median error function between the flatness template image and the reference image, and the minimum value of the median error function is determined as the matching result to achieve accurate positioning of the measurement area.

[0044] Figure 4 FIG. 1 is an exemplary flowchart showing the construction of a flatness template image according to an embodiment of the present application. Figure 4 As shown in , at step S401, the diameter parameter of the rolling ball is first set. The diameter of the rolling ball is different, and the pixel intensity of the final flatness template image will also be different. In the implementation scenario, the diameter parameter of the rolling ball can be set according to the pixel intensity to be obtained. Then, at step S402, it is determined whether the background of the measurement image is a black feature. That is, it is determined whether the pixel value of the corresponding pixel point in the measurement image is 0. If the background of the measurement image is a black feature, at step S403, a ball is used to roll and scan each pixel point in the measurement image row by row, and at step S404, the relatively flat pixel points exposed outside the pixel depression are removed. Further, at step S405, the remaining pixel values ​​are averaged and analyzed and counted, so as to obtain the flatness template image at step S406. For example, the pixel values ​​of the remaining pixels can be divided into columns, and the pixels in each column are averaged and analyzed and counted to construct the flatness template image of the relevant measurement area.

[0045] In addition, if the background of the measured image is not a black feature, in step S407, the pixel inversion operation is first performed on the image pixels in the measured image, and then the process jumps to step S402 to perform the above operations to obtain a flatness template image.

[0046] Figure 5 FIG. 1 is an exemplary flow chart showing the overall positioning of the wafer measurement area according to an embodiment of the present application. Figure 5 As shown in, at step S501, the wafer to be measured is loaded into the sample stage of the scanning electron microscope, and at step S502, the sample stage is moved so that the wafer is placed in the lens of the scanning electron microscope. Next, at step S503, the scanning electron microscope is used to perform addressing mode positioning on the area to be measured, and then at step S504, the fixed relationship between the area to be measured and the positioning addressing model in the addressing mode positioning method is used to complete the scanning of the measurement area through the deflection scanning coil and the moving deflection electron beam to obtain a measurement image. It should be understood that the aforementioned fixed relationship refers to the optimal matching position obtained by pattern matching based on the special form of the optical image in the scanning electron microscope to determine the approximate overall position to be measured, and the relationship between the actual area to be measured and the previously known positioning addressing is fixed.

[0047] Next, at step S505, first determine whether the X direction is positioned at the correct position. If the X direction is not positioned at the correct position, at step S506, directly position the measurement area by using the image template matching method. If the X direction has been positioned at the correct position, at step S507, along the Y direction according to the aforementioned pre-set area to be measured, at step S508, extract the measurement image of the measurement area. Further, at step S509, the image enhancement method of background removal is used to construct a flatness template image for the measurement image. For more details on constructing the flatness template image, please refer to Figure 2-Figure 4 The related description in the present application is not repeated here. Based on the constructed flatness template image, at step S510, the flatness template image is matched with the reference image to obtain a matching result, and at step S511, the measurement area is positioned according to the matching result. In an implementation scenario, the flatness template image can be matched with the reference image to obtain a matching result, for example, by finding the minimum value of the median error function.

[0048] Figure 6 FIG. 6 is an exemplary structural block diagram of a device 600 for positioning a wafer measurement area according to an embodiment of the present application. Figure 6As shown in , the device 600 of the present application may include a processor 601 and a memory 602, wherein the processor 601 and the memory 602 communicate with each other via a bus. The memory 602 stores program instructions for image alignment in wafer defect detection. When the program instructions are executed by the processor 601, the method steps described in the above text in combination with the accompanying drawings are implemented: collecting a measurement image and a reference image of a measurement area in a wafer; constructing a flatness template image related to the measurement area based on the measurement image; and matching the flatness template image with the reference image to obtain a matching result; and locating the measurement area according to the matching result.

[0049] According to the above description in combination with the accompanying drawings, those skilled in the art can also understand that the embodiments of the present application can also be implemented by software programs. Therefore, the present application also provides a computer-readable storage medium. The computer-readable storage medium stores computer-readable instructions for locating the wafer measurement area. When the computer-readable instructions are executed by one or more processors, the present application in combination with the accompanying drawings can be implemented. Figure 2 A method for locating a wafer metrology area is described.

[0050] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0051] It should be noted that although the operations of the method of the present application are described in a specific order in the accompanying drawings, this does not require or imply that the operations must be performed in this specific order, or that all the operations shown must be performed to achieve the desired results. On the contrary, the steps depicted in the flow chart can be performed in a different order. Additionally or alternatively, some steps can be omitted, multiple steps can be combined into one step, and / or one step can be decomposed into multiple steps.

[0052] It should be understood that when the terms "first", "second", "third" and "fourth" are used in the claims, the specification and the drawings of the present application, they are only used to distinguish different objects, rather than to describe a specific order. The terms "include" and "comprise" used in the specification and claims of the present application indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections.

[0053] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this application specification and claims, unless the context clearly indicates otherwise, the singular forms of "a", "an" and "the" are intended to include plural forms. It should also be further understood that the term "and / or" used in this application specification and claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0054] Although the implementation methods of the present application are as above, the contents described are only examples adopted to facilitate the understanding of the present application, and are not intended to limit the scope and application scenarios of the present application. Any technician in the technical field described in the present application can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present application, but the scope of patent protection of the present application shall still be subject to the scope defined in the attached claims.

Claims

1. A method for locating a wafer measurement area, comprising: Acquire a measurement image and a reference image of a measurement area in a wafer; constructing a flatness template image related to the measurement area based on the measurement image; as well as Using the flatness template image to match the reference image to obtain a matching result; as well as Positioning the measurement area according to the matching result, Wherein constructing a flatness template image related to the measurement area based on the measurement image comprises: performing a background removal operation on the measurement image; and Performing signal intensity analysis on the measured image after background removal to construct a flatness template image related to the measured area; The matching of the flatness template image with the reference image to obtain a matching result includes: Calculating a median value of the reference image; Calculating a median error function between the flatness template image and the reference image based on an absolute value of a difference between each pixel in the flatness template image and the median; and The position corresponding to the minimum value of the median error function is determined as the matching point to obtain the matching result. 2 . The method according to claim 1 , wherein the measurement image and the reference image are acquired along a longitudinal direction of the measurement area.

3. The method according to claim 1, wherein performing a background removal operation on the measurement image comprises: A ball is used to roll and scan each pixel point in the measurement image line by line, and the pixel points that can be touched by the ball are removed to perform a background removal operation on the measurement image.

4. The method according to claim 1, wherein performing signal intensity analysis on the measurement image after background removal to construct a flatness template image related to the measurement area comprises: The pixel mean value of the pixels in the measurement image after the background is removed is calculated along the longitudinal direction to construct a flatness template image related to the measurement area.

5. The method according to claim 1 or 3, wherein before performing a background removal operation on the measurement image, it further comprises: Determining whether the background of the measurement image is a black feature; as well as In response to the background of the measurement image not being the black feature, a pixel inversion operation is performed on image pixels in the measurement image.

6. A device for positioning a wafer measurement area, comprising: processor; as well as A memory having computer instructions for locating a wafer measurement area stored thereon, wherein when the computer instructions are executed by a processor, the method according to any one of claims 1-5 is implemented.

7. A computer-readable storage medium having stored thereon computer program instructions for locating a wafer measurement area, wherein when the computer program instructions are executed by one or more processors, the method according to any one of claims 1 to 5 is implemented.

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