A method for optimizing the brightness of square holes in a mask via layer

Abstract

This invention discloses a method for optimizing the brightness of square holes in a mask through-hole layer. The method includes the following steps: S01: Locating and calibrating the coverage area of ​​each square hole on the Mask image and the generated mask design file; S02: Calculating the histogram of the original grayscale value of each pixel in the coverage area of ​​the square hole on the Mask image, defining a light-dark boundary value, designating areas above the light-dark boundary value as bright areas, and using the peak point of the grayscale histogram of the bright areas as grayscale marker values. Then, the original grayscale value of each pixel in the coverage area of ​​each square hole is marked with the corresponding grayscale marker value, resulting in a square hole grayscale image B. This method can optimize the brightness of square holes on the Mask image, preserving the characteristics of defects while effectively reducing the difference in pixel grayscale between the generated mask design file image and the actual Mask image, which is beneficial for defect detection.

Description

Technical Field

[0001] This invention relates to a method for optimizing the brightness of square holes in the through-hole layer of a photomask, belonging to the field of semiconductor detection technology. Background Technology

[0002] Masks are used to transfer circuit patterns during semiconductor manufacturing. The CNT (Through-Nut) layer on a mask refers to the via structure used to connect different metal layers in a multilayer metallization process. These vias allow current to flow from one metal layer to another, enabling vertical interconnection of circuits. Larger masks may be used to manufacture larger integrated circuit boards. When the mask size is large, the unevenness of the light source becomes more pronounced during mask inspection. The unevenness of the mask's background light source can cause uneven brightness in individual square holes in the via layer image, leading to an excessive number of false defects and the omission of true defects in the detection of square holes. Therefore, in addition to addressing the unevenness of the detection light source at the hardware level, mitigating the impact of unevenness at the algorithm level is crucial to ensuring the accuracy of CNT layer detection and improving production efficiency.

[0003] The brightness of individual square holes in the CNT image of the Mask image acquired by the camera is uneven. However, the image generated by the design file (including but not limited to design file formats such as GDS and OASIS) (i.e., the generated image of the mask design file) has uniform and close gray values ​​within the square hole range. This can equalize the gray values ​​of the unevenly bright square holes to be close to the uniformity of the square holes in the generated image of the mask design file, so that the generated image of the mask design file can match the Mask image acquired by the camera well. This is the key to ensuring the accuracy and error rate of defect detection. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for optimizing the brightness of square holes in the through-hole layer of a mask. This method can optimize the brightness of square holes on the mask image, thereby preserving the characteristics of defects and facilitating defect detection.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for optimizing the brightness of square holes in the through-hole layer of a photomask, the method comprising the following steps:

[0006] S01: Locate and calibrate the coverage area of ​​each square hole on the Mask diagram and the generated mask design file;

[0007] S02: Calculate the histogram for the original grayscale value of each pixel in the area covered by the square hole on the Mask image, define the light and dark boundary value, take the area above the light and dark boundary value as the bright area, and take the grayscale peak point of the bright area as the grayscale mark value. Then mark the original grayscale value of each pixel in the area covered by each square hole as the corresponding grayscale mark value to obtain the grayscale image B of the square hole.

[0008] S03: Calculate the grayscale simulated background value C of each pixel in the generated image of the mask design file based on the original grayscale value of each pixel and its neighboring pixels, and calculate the grayscale simulated background value D of each pixel in the Mask image based on the grayscale value image B of the square hole and its neighboring pixels.

[0009] S04: Based on the grayscale simulated background value C of each pixel and its neighboring pixels obtained in step S03, calculate the reference brightness value E of each pixel in the generated image of the mask design file and the reference brightness value F of each pixel in the Mask image based on the grayscale simulated background value D of each pixel and its neighboring pixels obtained in step S03. Subtract the reference brightness value F from the reference brightness value E to obtain the reference brightness change value G: If G is positive, it means that the brightness of the pixel position needs to be increased and the grayscale value increased; if G is negative, it means that the brightness of the pixel position needs to be decreased and the grayscale value decreased.

[0010] S05: Calculate the grayscale offset value I. Add the grayscale offset value I to the original grayscale value H of the corresponding pixel on the Mask image to obtain the optimized grayscale value; where I = H * G / E.

[0011] Furthermore, step S01 specifically includes:

[0012] S011: Locate the coverage area of ​​the square hole and define the square hole features. Mark the square hole marker points for each pixel point within the coverage area that conforms to the square hole features.

[0013] S012: Fit all square hole marker points within the coverage area of ​​the corresponding square hole to a representative point of the square hole position to mark the pixel points within the coverage area that conform to the square hole feature.

[0014] In step S012, the coordinates of the representative point of the square hole position within the corresponding square hole coverage area are the average of the coordinates of all square hole marker points within the corresponding square hole coverage area.

[0015] Furthermore, in step S03, the grayscale simulated background value of the corresponding pixel is calculated as follows: take M pixels with grayscale values ​​arranged in descending order from the surrounding N*N range of the corresponding pixel, calculate the average grayscale value of these M pixels, and use it as the grayscale simulated background value of the pixel.

[0016] Furthermore, N*N has a range of 3*3; and / or M is 4.

[0017] Furthermore, in step S04, the reference brightness value of the corresponding pixel is calculated as follows: Reference brightness value of the corresponding pixel = grayscale simulated background value of the corresponding pixel + half of the grayscale simulated background values ​​of the pixels at the top, bottom, left, and right positions of the pixel + 1 / 4 of the grayscale simulated background values ​​of the pixels at the top left, bottom left, top right, and bottom right corners of the pixel.

[0018] Furthermore, in step S05, it is determined whether the grayscale value of the corresponding pixel on the Mask image is greater than the set minimum detection grayscale value. If it is greater, the brightness of the pixel is optimized.

[0019] After adopting the above technical solution, the method of the present invention performs brightness equalization on the pixel values ​​of each individual square hole image that is uneven on the Mask image, so that the pixel values ​​of the overly bright parts after comparison with the generated image of the mask design file are reduced to a suitable brightness. It can improve the brightness of the dark parts while retaining the brightness pixel values ​​of the dark parts of the defective parts, thereby preserving the characteristics of the defect.

[0020] Compared with existing technologies, the present invention has the following advantages: (1) It can optimize the gray value of the pixel value of the actual photographed image of the square hole without adjusting the brightness of the light source through hardware, so that the gray value is close to the gray value of the generated image of the mask design file; (2) It can perform gray-scale equalization on both bright and dark areas, reduce the gray value of the brighter areas and increase the gray value of the darker areas; (3) It can preserve the details of the dark areas without affecting the brightness of the defective parts, thus ensuring the detection accuracy. Attached Figure Description

[0021] Figure 1 The mask image acquired by the camera of this invention;

[0022] Figure 2 This is a magnified view of a portion of the Mask image acquired by the camera of this invention;

[0023] Figure 3 This is a diagram showing the generation of the mask design file for the present invention;

[0024] Figure 4 This is a partial enlarged view of the mask design file generation diagram of the present invention.

[0025] Figure 5 This is a diagram showing the position markings of the square holes in this invention;

[0026] Figure 6 This is a partial enlarged view of the square hole position marking diagram of the present invention. Detailed Implementation

[0027] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0028] like Figures 1-6 As shown, a method for optimizing the brightness of square holes in a through-hole layer of a photomask includes the following steps:

[0029] S01: Locate and calibrate the coverage area of ​​each square hole on the Mask diagram and the generated mask design file;

[0030] S02: Calculate the histogram for the original grayscale value of each pixel in the area covered by the square hole in the Mask image, define the light and dark boundary value, and take the area above the light and dark boundary value as the bright area. Then, mark the original grayscale value of each pixel in each area covered by the square hole as the corresponding grayscale mark value to obtain the grayscale image B of the square hole; the light and dark boundary value can be 128.

[0031] S03: Calculate the grayscale simulated background value C of each pixel in the generated image of the mask design file based on the original grayscale value of each pixel and its neighboring pixels, and calculate the grayscale simulated background value D of each pixel in the Mask image based on the grayscale value image B of the square hole and its neighboring pixels.

[0032] S04: Based on the grayscale simulated background value C of each pixel and its neighboring pixels obtained in step S03, calculate the reference brightness value E of each pixel in the generated image of the mask design file and the reference brightness value F of each pixel in the Mask image based on the grayscale simulated background value D of each pixel and its neighboring pixels obtained in step S03. Subtract the reference brightness value F from the reference brightness value E to obtain the reference brightness change value G: If G is positive, it means that the brightness of the pixel position needs to be increased and the grayscale value increased; if G is negative, it means that the brightness of the pixel position needs to be decreased and the grayscale value decreased.

[0033] S05: Calculate the grayscale offset value I. Add the grayscale offset value I to the original grayscale value H of the corresponding pixel on the Mask image to obtain the optimized grayscale value; where I = H * G / E.

[0034] Specifically, step S01 is as follows:

[0035] S011: Locate the coverage area of ​​the square hole and define the square hole features. Mark the square hole marker points for each pixel point within the coverage area that conforms to the square hole features.

[0036] S012: Fit all square hole marker points within the coverage area of ​​the corresponding square hole to a representative point of the square hole position to mark the pixel points within the coverage area that conform to the square hole feature.

[0037] In step S012, the coordinates of the representative point of the square hole position within the corresponding square hole coverage area are the average of the coordinates of all square hole marker points within the corresponding square hole coverage area.

[0038] Specifically, in step S03, the grayscale simulated background value of the corresponding pixel is calculated as follows: take M pixels with grayscale values ​​arranged in descending order from the surrounding N*N range of the corresponding pixel, calculate the average grayscale value of these M pixels, and use it as the grayscale simulated background value of the pixel.

[0039] Specifically, N*N can be in the range of 3*3; M can be 4.

[0040] Specifically, in step S04, the reference brightness value of the corresponding pixel is calculated as follows: Reference brightness value of the corresponding pixel = grayscale simulated background value of the corresponding pixel + half of the grayscale simulated background values ​​of the pixels at the top, bottom, left, and right positions of the pixel + 1 / 4 of the grayscale simulated background values ​​of the pixels at the top left, bottom left, top right, and bottom right corners of the pixel.

[0041] Specifically, in step S05, it is determined whether the gray value of the corresponding pixel on the Mask image is greater than the set minimum detection gray value. If it is greater, the brightness of the pixel is optimized.

[0042] The specific embodiments described above further illustrate the technical problems, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing the brightness of square holes in a through-hole layer of a photomask, characterized in that... The steps of the method include: S01: Locate and calibrate the coverage area of ​​each square hole on the Mask diagram and the generated mask design file; S02: Calculate the histogram for the original grayscale value of each pixel in the area covered by the square hole on the Mask image, define the light and dark boundary value, take the area above the light and dark boundary value as the bright area, and take the grayscale peak point of the bright area as the grayscale mark value. Then mark the original grayscale value of each pixel in the area covered by each square hole as the corresponding grayscale mark value to obtain the grayscale image B of the square hole. S03: Calculate the grayscale simulated background value C of each pixel in the generated image of the mask design file based on the original grayscale value of each pixel and its neighboring pixels, and calculate the grayscale simulated background value D of each pixel in the Mask image based on the grayscale value image B of the square hole and its neighboring pixels. S04: Based on the grayscale simulated background value C of each pixel and its neighboring pixels obtained in step S03, calculate the reference brightness value E of each pixel in the generated image of the mask design file and the reference brightness value F of each pixel in the Mask image based on the grayscale simulated background value D of each pixel and its neighboring pixels obtained in step S03. Subtract the reference brightness value F from the reference brightness value E to obtain the reference brightness change value G: If G is positive, it means that the brightness of the pixel needs to be increased and the grayscale value increased; if G is negative, it means that the brightness of the pixel needs to be decreased and the grayscale value decreased. S05: Calculate the grayscale offset value I. Add the grayscale offset value I to the original grayscale value H of the corresponding pixel on the Mask image to obtain the optimized grayscale value; where I = H * G / E; In step S03, the grayscale simulated background value of the corresponding pixel is calculated as follows: take M pixels with grayscale values ​​arranged in descending order from the surrounding N*N range of the corresponding pixel, calculate the average grayscale value of these M pixels, and use it as the grayscale simulated background value of the pixel. In step S04, the reference brightness value of the corresponding pixel is calculated as follows: Reference brightness value of the corresponding pixel = grayscale simulated background value of the corresponding pixel + half of the grayscale simulated background values ​​of the pixels at the top, bottom, left, and right positions of the pixel + half of the grayscale simulated background values ​​of the pixels at the top left, bottom left, top right, and bottom right corners of the pixel.

2. The method according to claim 1, characterized in that, Step S01 is as follows: S011: Locate the coverage area of ​​the square hole and define the square hole features. Mark the square hole marker points for each pixel point within the coverage area that conforms to the square hole features. S012: Fit all square hole marker points within the coverage area of ​​the corresponding square hole to a unique square hole location representative point to mark the pixel points within the coverage area that conform to the square hole feature.

3. The method according to claim 2, characterized in that, In step S012, the coordinates of the representative point of the square hole position within the corresponding square hole coverage area are the average of the coordinates of all square hole marker points within the corresponding square hole coverage area.

4. The method according to claim 1, characterized in that, The range of N*N is 3*3; and / or M is 4.

5. The method according to claim 1, characterized in that, In step S05, it is determined whether the gray value of the corresponding pixel on the Mask image is greater than the set minimum detection gray value. If it is greater, the brightness of the pixel is optimized.

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