TW202020933A - Method for optimizing focal parameters of lithographic process - Google Patents

Abstract

A method for optimizing focal parameters of lithographic process includes:　Performing a first image capturing step on a first measured pattern with a plurality of focus points; selecting a plurality of the first pattern images corresponding to an intermediate value of the focus from the first pattern images and stacking the selected first pattern images to form a first reference image; removing a plurality of error images from the first pattern images; selecting at least two of the remaining first pattern images corresponding to the intermediate value from the remaining first pattern images and stacking the selected remaining first pattern images to form a first standard image; performing a first similarity analysis on the remaining first pattern images according to the first standard image to obtain a plurality of first image scores; and obtained an optimized focal location according to the first image scores.

Description

Method for optimizing lithographic focusing parameters

This specification relates to a semiconductor process, and particularly to a yellow light lithography process.

In semiconductor process technology, when a pattern is to be transferred from a photomask to a photoresist, energy is needed to activate the photoresist. The source of energy is generally provided by radiation, such as an ultraviolet light source (UV). Focus is to focus the radiant energy of radiated light on a single point. The accuracy of focusing directly affects the accuracy of the lithography process. Generally speaking, different pattern designs require different radiant energy and different focus positions. Conventional technology usually monitors the focus of the lithography process by examining the critical dimension (CD), line end shortening (LES) and side wall angle (SWA) parameters of the exposed pattern to optimize the process quality. Among them, the shortening of the end of the line refers to the difference between the actual printing position and the predetermined position of the photoresist at the end of the line; the side wall angle refers to the profile of the photoresist after energy exposure.

However, the key dimensions, the shortening of the end of the line, and the angle of the side walls are all measured by the detection device to measure the diffraction value of the light emitted from the reticle, and then obtained by simulation. In the case of excessive background noise, lithography out of focus, or measurement position error, incorrect parameter information will continue to be provided, and abnormal conditions cannot be immediately reflected, resulting in monitoring failure and inability to obtain better focus to optimize the micro The operating quality of the shadow process.

Therefore, there is a need to provide a more advanced method for optimizing the lithographic focusing parameters to improve the problems faced by conventional technologies.

One aspect of this specification is about a method for optimizing lithographic focusing parameters, including the following steps: First, the first image capturing step is performed on the first test pattern with a plurality of focus positions to obtain a plurality of The first pattern image. Then, a plurality of first pattern images corresponding to the intermediate values of the focus positions are selected from the first pattern images, and a first overlay step is performed to form a first reference image. Then, based on the first reference image, a plurality of erroneous images are removed from the first pattern images. Then, at least two of the plurality of remaining first pattern images corresponding to the intermediate values of the focal points are selected, and a second overlay step is performed to form a first standard image. Subsequently, a first similarity analysis is performed on the remaining first pattern images according to the first standard image to obtain a plurality of first image scores, and thereby determine the best focus position.

According to the above embodiments, this specification provides a method for optimizing lithographic focusing parameters. It uses an image analysis method, first selecting multiple focal positions including a better focal length range to capture a pattern image. Afterwards, a plurality of pattern images are selected from a plurality of pattern images corresponding to the intermediate values of the focal positions for overlay, to form a plurality of reference images. The reference image is compared with the captured pattern image for image comparison and analysis, so as to eliminate false images caused by factors such as excessive background noise, lithography out of focus, or measurement position error. After erroneous and erroneous images are removed, at least two of the remaining pattern images corresponding to the median value of the focus position are selected to perform another overlay, to obtain a plurality of standard images. The standard image and the remaining pattern images are compared and analyzed again to calculate the image score that can represent the quality of each remaining pattern image, and then statistical analysis is performed according to the image score to obtain the best focus position. In some embodiments, the image score refers to the degree of correlation between each remaining pattern image and its corresponding standard image.

With the lithographic focusing parameter optimization method provided by the above embodiment of the present invention, erroneous images that may cause measurement failures can be eliminated in the lithography process in real time, ensuring process monitoring and obtaining better focus to optimize lithography Operational quality of the process.

This manual discloses a method for optimizing lithographic focusing parameters. In order to make the above embodiments and other objects, features, and advantages of the present specification more obvious and understandable, a few preferred embodiments are described below in conjunction with the accompanying drawings for detailed description. However, it must be noted that these specific implementation examples and methods are not intended to limit the present invention. The present invention can still be implemented using different features, elements, methods, and parameters of other embodiments. The proposed preferred embodiments are only used to illustrate the technical features of the present invention, and are not intended to limit the patent application scope of the present invention. Those with ordinary knowledge in this technical field will be able to make equal modifications and changes based on the description of the following description without departing from the spirit of the present invention. In different embodiments and drawings, the same elements will be denoted by the same element symbols.

Please refer to FIG. 1, which is a flowchart of a method for optimizing lithographic focusing parameters according to an embodiment of the present specification. Wherein, the method for optimizing the lithography focusing parameters includes the following steps: First, an image capturing step is performed on at least one measured pattern with a plurality of focus positions to obtain a plurality of pattern images (step 101).

In some embodiments of the present specification, the image capturing step may select a plurality of local patterns (tested patterns) at different positions for image capturing according to the circuit layout to be transferred in the lithography process. In addition, in some embodiments, different light energy (for example, ultraviolet light) may also be used to illuminate the same test pattern to capture different pattern images. Among them, the selection of the plurality of focus positions may be based on the critical size of the circuit layout, the complexity of the pattern, or other process factors, and may select multiple focus positions that may be included in the better focal length range to capture the pattern image.

For example, please refer to FIG. 2, according to an embodiment of the present specification, FIG. 2 shows the result after image capturing of at least one tested pattern. In this implementation, three different light energies are used, such as energy 1 (such as 23.5 microjoule (mJ)), energy 2 (such as 32.2 microjoules) and energy 3 (such as 28 microjoules), with 11 different The focal position of the lens (the focal length is arranged from small to large, respectively, the focal length is -5 microns (micrometer, µm), -4 microns, -3 microns, -2 microns, -1 microns, 0 microns, 1 microns, 2 microns, 3 microns , 4 microns and 5 microns), respectively for 5 different tested patterns, such as the first tested pattern 201A, the second tested pattern 201B, the third tested pattern 201C, the fourth tested pattern 201D and the fifth tested Pattern 201E, image capture, a total of 165 (3×11×5) pattern images were obtained.

As shown in FIG. 2, each of the three solid boxes above, middle, and below includes using different light energies (such as energy 1, energy 2, and energy 3) for the first test pattern 201A, The second tested pattern 201B, the third tested pattern 201C, the fourth tested pattern 201D, and the fifth tested pattern 201E perform 55 pattern images obtained by image capturing. In addition, according to the tested patterns (first tested pattern 201A, second tested pattern 201B, third tested pattern 201C, fourth tested pattern 201D, and fifth tested pattern 201E), these 165 pattern images can be It is divided into three groups, namely a first pattern image 202A, a second pattern image 202B, a third pattern image 202C, a fourth pattern image 202D, and a fifth pattern image 202D.

Among them, the first pattern image 202A includes 11 images (in the first row in the upper solid box) using energy 1 to capture the pattern images, 11 images (in the middle solid box in the first row) using energy 2 The captured pattern images and 11 images (located in the first row in the solid box below) using energy 3 captured pattern images. The second pattern image 202B contains 11 images (in the second row in the solid box above) using energy 1 to capture the pattern images, and 11 images (in the middle solid box in the second row) using energy 2 to capture The pattern images and 11 images (located in the second row in the solid box below) using energy 3 captured the pattern images. The third pattern image 202C contains 11 images (in the third row in the solid box above) using energy 1 and 11 images (in the third solid box in the middle) using energy 2 The pattern images and 11 images (located in the third row in the solid box below) using the energy 3 captured pattern images. The fourth pattern image 202D contains 11 images (in the fourth row in the solid box above) that were captured with energy 1 and 11 images (in the fourth row in the middle solid box) were captured with energy 2 The pattern images and 11 images (located in the fourth row in the solid box below) using the energy 3 captured pattern images. The fifth pattern image 202E contains 11 images (in the fifth row in the upper solid box) using energy 1 to capture the pattern images, and 11 images (in the middle solid box in the fifth row) using energy 2 to capture The pattern images and 11 images (located in the fifth row in the solid box below) using the energy 3 to capture the pattern images.

However, it is worth noting that the number of the tested pattern, the energy used, the focus position and the pattern image are not limited to this. Any person with ordinary knowledge in the technical field can choose the desired pattern according to actual needs , Energy and focus, and increase or decrease the number of elements described above.

After that, a plurality of pattern images corresponding to the intermediate value of the focus position are selected from each group of pattern images, and the first image overlay step is performed to form a plurality of reference images (step 102). For example, please refer to FIG. 3, which illustrates the selection of 12 third pattern images corresponding to the median value (0 microns) of 11 focus positions from the 55 third pattern images 202C in FIG. 2 (such as (Represented by the dotted box), and the selected 12 third pattern images are subjected to the first overlay step 204 to form a reference image 203.

In some embodiments of the present specification, the first overlay step 204 overlaps the selected 12 third pattern images to form a third reference image 203 with overlapping images. At the same time, the first pattern image 202A, the second pattern image 202B, the fourth pattern image 202D, and the fifth pattern image 202D also use the same method to perform the above-mentioned first overlay step 204 to form a first image with overlapping images. Reference image, second reference image, fourth reference image and fifth reference image (not shown).

In some embodiments of the present specification, before performing the first image stacking step 204, a noise filtering step may be optionally performed on the selected 12 third pattern images. For example, in this embodiment, Gaussian Blur technology is used to pre-process the selected 12 third pattern images to reduce image noise.

Next, according to the first reference image, the second reference image (not shown), the third reference image 203, the fourth reference image, and the fifth reference image (not shown), the first pattern image 202A, the second pattern image 202B , The third pattern image 202C, the fourth pattern image 202D, and the fifth pattern image 202E remove a plurality of error images (step 103). In some implementations of this specification, the steps of removing a plurality of erroneous images from the first pattern image 202A, the second pattern image 202B, the third pattern image 202C, the fourth pattern image 202D, and the fifth pattern image 202E may be Including calculating the IOU (intersection-over-union, IOU) index of each first pattern image 202A and the first reference image; calculating the IOU index of each second pattern image 202B and the second reference image; calculating each third pattern The IOU index of the image 202C and the third reference image 203; the IOU index of each fourth pattern image 202D and the fourth reference image and the IOU index of each fifth pattern image 202E and the fifth reference image are calculated. After that, one or more (or possibly zero) first pattern images 202A, second pattern images 202B, third pattern images 202C, fourth pattern images 202D, and fifth pattern images having a value less than a predetermined IOU index value are deleted 202E.

Please refer to FIG. 4. FIG. 4 is a simplified schematic diagram of a method for calculating the IOU indicators of a pattern image and a reference image according to an embodiment of this specification. Taking the third pattern image 202C and the third reference image 203 as an example, a method of calculating the IOU index of each third pattern image 202C and the third reference image 203 includes the step of each third pattern image 202C and the third reference image 203 The intersection of the two images is divided by the combined portion of the two images. The intersection of the third pattern image 202C and the third reference image 203 refers to the image area A1 where the third pattern image 202C and the third reference image 203 overlap each other. The combined image portion of the third pattern image 202C and the third reference image 203 refers to the image area A2 of the third pattern image 202C that does not overlap with the third reference image 203, plus the third reference image 203 and the third The image area A3 where the pattern image 202C overlaps, plus the image area A1 where the two overlap. The IOU index can be expressed by formula (1): IOU=A1/(A1+A2+A3) .... (1) In this embodiment, referring to the calculated result, delete the IOU index value is less than the custom lower limit 11 wrong third pattern images 202C (as shown by the solid boxes in Figure 3), leaving 22 remaining third pattern images 202C.

In some embodiments of the present specification, the steps of removing a plurality of erroneous images from the first pattern image 202A, the second pattern image 202B, the third pattern image 202C, the fourth pattern image 202D, and the fifth pattern image 202E, also It may include evaluating the correlation between each first pattern image 202A and the first reference image; evaluating the correlation between each second pattern image 202B and the second reference image; evaluating each third pattern image 202C and the first The correlation between the three reference images 203; evaluating the correlation between each fourth pattern image 202D and the fourth reference image and evaluating the correlation between each fifth pattern image 202E and the fifth reference image. After that, one or more (or possibly zero) first patterns with a low degree of correlation with the corresponding first reference image, second reference image, third reference image, fourth reference image, and fifth reference image are deleted The image 202A, the second pattern image 202B, the third pattern image 202C, the fourth pattern image 202D, and the fifth pattern image 202E.

來代表；第三參考影像203的影像畫素值，可以由一個25個數字元素構成的第二矩陣

來代表。接著，分別將第一矩陣和第二矩陣轉換為一個25個數字元素所構成的數列。例如，將第一矩陣轉換為第一數列A(x)：[0 6 12.... 132 138 134]；將第二矩陣轉換為第二數列B(y)：[50 52 54....94 96 98]。計算第一數列A(x)和第二數列B(y)的相關係數r_xy ，相關係數r_xy 以算式(2)表示：

其中S_x 和S_y 分別為第一數列A(x)和第二數列B(y)的標準差。在本實施例中，參照計算所得的結果，刪除相關係數數值小於自訂的值的11張錯誤的第三圖案影像202C(如第3圖實線方框所繪示)，餘留下22個剩餘的第三圖案影像202C。Taking the third pattern image 202C and the third reference image 203 as examples, the step of evaluating the correlation between each third pattern image 202C and the third reference image 203 includes calculating each third pattern image 202C and the third reference Correlation coefficient between images 203. First, the pixel values of one of the third pattern images 202C and the third reference image 203 are obtained respectively. For example, in this embodiment, the pixel value of one of the third pattern images 202C may be a first matrix composed of 25 digital elements

To represent; the image pixel value of the third reference image 203 can be a second matrix of 25 digital elements

To represent. Next, the first matrix and the second matrix are converted into a sequence of 25 digital elements, respectively. For example, convert the first matrix to the first sequence A(x): [0 6 12.... 132 138 134]; convert the second matrix to the second sequence B(y): [50 52 54... .94 96 98]. Calculating a first number of columns in A (x) and a second number of columns B (y) of correlation coefficient r _xy, the correlation coefficient r _xy represented by formula (2):

Where S _x and S _y are the standard deviations of the first series A(x) and the second series B(y), respectively. In this embodiment, referring to the calculated result, 11 erroneous third pattern images 202C (as shown by the solid line boxes in FIG. 3) with the correlation coefficient value less than the customized value are deleted, leaving 22 The remaining third pattern image 202C.

It is worth noting that the steps of removing a plurality of erroneous images from the first pattern image 202A, the second pattern image 202B, the third pattern image 202C, the fourth pattern image 202D, and the fifth pattern image 202E can be performed separately. The calculation of indicators or the evaluation of correlations alone can also include both.

Then, at least two of the plurality of remaining pattern images corresponding to the middle value of the focus are selected, and a second overlay step 205 is performed to form a standard image (step 104). Please refer to FIG. 5. FIG. 5 illustrates an implementation method of performing the second step 205 of superimposing images after removing a plurality of erroneous images according to an embodiment of the present specification. In some embodiments of this specification, the second overlay step 205 includes the following steps: First, the remaining first pattern image 202A and the second pattern after the plurality of erroneous images (indicated by crosses) have been removed Among the image 202B, the third pattern image 202C, the fourth pattern image 202D, and the fifth pattern image 202E, a plurality of pattern images captured with the same light energy are selected respectively. For example, in this embodiment, 11 first pattern images 202A, 11 second pattern images 202B, 7 third pattern images 202C, 10 fourth pattern images 202D, and 9 first Five pattern image 202E.

Then, the pattern images (11 first pattern images 202A, 11 second pattern images 202B, 7 third pattern images 202C, 10 fourth pattern images 202D, and 9 images) captured by the same light energy are used. In the fifth pattern image 202E), select a plurality of pattern images (for example, three first pattern images 202A and three second patterns shown as dotted boxes, respectively, corresponding to the median value of the focal position (the focal length is 0 μm) Image 202B, three third pattern images 202C, three fourth pattern images 202D and three fifth pattern images 202E), and then three selected first pattern images 202A, three second pattern images 202B, Three third pattern images 202C, three fourth pattern images 202D, and three fifth pattern images 202E are subjected to a second overlay step 205, thereby forming a first standard image 206A, a second standard image 206B, and a second standard image with overlapping images Three standard images 206C, fourth standard images 206D and fifth standard images 206E.

Wherein, the implementation method of the second overlay step 205 is roughly similar to the aforementioned first overlay step 204, all of which select the pattern image corresponding to the intermediate value of the focus position. The only difference is that the pattern image selected in the second overlay step 205 must be a pattern image captured with the same light energy.

Subsequently, based on the first standard image 206A, the second standard image 206B, the third standard image 206C, the fourth standard image 206D, and the fifth standard image 206E, the remaining first pattern after the erroneous image (represented by a cross) is removed Image 202A, second pattern image 202B, third pattern image 202C, fourth pattern image 202D, and fifth pattern image 202E, perform similarity analysis to obtain a plurality of first image scores, second image scores, and third images, respectively Score, fourth image score and fifth image score (step 105).

In some embodiments of this specification, the similarity analysis based on the first standard image 206A, the second standard image 206B, the third standard image 206C, the fourth standard image 206D, and the fifth standard image 206E includes calculating each The first correlation coefficient between the remaining first pattern image 202A and the first standard image 20A6, and the second correlation coefficient between each remaining second pattern image 202B and the second standard image 206B Calculate the third correlation coefficient between each remaining third pattern image 202C and the third standard image 206C, and calculate the difference between each remaining fourth pattern image 202D and the fourth standard image 206D The fourth correlation coefficient and the fifth correlation coefficient between each remaining fifth pattern image 202E and the fifth standard image 206E are calculated.

Each of the obtained first correlation coefficient, second correlation coefficient, third correlation coefficient, fourth correlation coefficient, and fifth correlation coefficient, after normalization of the data, can be used as each remaining first The first image score, the second image score, the third image score, the fourth image score, and the fifth of the pattern image 202A, the second pattern image 202B, the third pattern image 202C, the fourth pattern image 202D, and the fifth pattern image 202E Image score.

Subsequently, the best focus position is determined by the first image score, the second image score, the third image score, the fourth image score, and the fifth image score (step 106). In some embodiments of the present specification, the step of determining the optimal focus position includes: according to each remaining first pattern image 202A, second pattern image 202B, third pattern image 202C, fourth pattern image 202D, and the first The first image score, the second image score, the third image score, the fourth image score, and the fifth image score of the five-pattern image 202E, together with their corresponding focus positions (focal length), are respectively made into a first focus-image A score relationship curve 601, a second focus-image score relationship curve 602, a third focus-image score relationship curve 603, a fourth focus-image score relationship curve 604, and a fifth focus-image score relationship curve 605.

For example, please refer to FIG. 6, which is a plurality of focus-image score relationship curves used to determine the optimal focus position according to an embodiment of the present specification. In Fig. 6, the horizontal axis is the focal position (focal length), and the vertical axis is the normalized image score. Among them, the focal point position is distributed between a focal length of -6 microns and 6 microns, and the image score is distributed between -0.1 and 0.1. This displays each remaining first pattern image 202A, second pattern image 202B, third pattern image 202C, fourth pattern image 202D, and fifth pattern image 202E, respectively with the first standard image 206A and the second standard image 206B The third standard image 206C, the fourth standard image 206D, and the fifth standard image 206E have extremely high similarities. In other words, most of the failed images due to excessive background noise, lithography out of focus, or measurement position errors have been eliminated.

Next, the first focus-image score relationship curve 601, the second focus-image score relationship curve 602, the third focus-image score relationship curve 603, the fourth focus-image score relationship curve 604, and the fifth focus-image score are respectively analyzed. The image score of the relationship curve 605 is subjected to linear regression to obtain a curve of second order 606. Then, the quadratic curve 605 is differentiated, and the coordinates of the vertex 607 of the obtained quadratic curve 606 are the optimal focus positions. In this embodiment, the optimal focus position is 0.45 microns.

According to the above embodiments, this specification provides a method for optimizing lithographic focusing parameters. It uses an image analysis method, first selecting multiple focal positions including a better focal length range to capture a pattern image. Afterwards, a plurality of pattern images are selected from a plurality of pattern images corresponding to the intermediate values of the focal positions for overlay, to form a plurality of reference images. The reference image is compared with the captured pattern image for image comparison and analysis, so as to eliminate false images caused by factors such as excessive background noise, lithography out of focus, or measurement position error. After erroneous and erroneous images are removed, at least two of the remaining pattern images corresponding to the median value of the focus position are selected to perform another overlay, to obtain a plurality of standard images. The standard image and the remaining pattern images are compared and analyzed again to calculate the image score that can represent the quality of each remaining pattern image, and then statistical analysis is performed according to the image score to obtain the best focus position. In some embodiments, the image score refers to the degree of correlation between each remaining pattern image and its corresponding standard image.

With the lithographic focusing parameter optimization method provided by the above embodiment of the present invention, erroneous images that may cause measurement failures can be eliminated in the lithography process in real time, ensuring process monitoring and obtaining better focus to optimize lithography Operational quality of the process.

Although this specification has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in this technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be deemed as defined by the appended patent application scope.

101: Perform image capturing steps on at least one tested pattern with a plurality of focus positions to obtain a plurality of pattern images 102: Select a plurality of pattern images corresponding to the intermediate value of the focus position from the plurality of pattern images, and perform the first Steps to form a plurality of reference images 103: remove a plurality of error images from the plurality of pattern images based on these reference images 104: select at least two of the plurality of remaining pattern images corresponding to the intermediate value of the focus position , Perform the second overlay step to form a plurality of standard images 105: perform similarity analysis on the remaining pattern images after removing the plurality of error images according to these standard images to obtain a plurality of image scores 106 respectively: by these Image score to determine the best focus position 201A: first tested pattern 201B: second tested pattern 201C: third tested pattern 201D: fourth tested pattern 201E: fifth tested pattern 202A: first pattern image 202B: Second pattern image 202C: Third pattern image 202D: Fourth pattern image 202D: Fifth pattern image 204, 205: Overlay step 203: Third reference image 206A: First standard image 206B: Second standard image 206C : Third standard image 206D: Fourth standard image 206E: Fifth standard image 601, 602, 603, 604, 605: Focus-image score relationship curve 606: Quadratic curve 607: Vertex of quadratic curve

In order to make the above-mentioned embodiments of the invention and other objects, features and advantages more obvious and understandable, several preferred embodiments are described in detail in conjunction with the attached drawings, and the detailed descriptions are as follows: A flow chart of a method for optimizing lithographic focusing parameters as shown in the embodiment; FIG. 2 is a result of image capturing of at least one tested pattern according to an embodiment of the present specification; FIG. 3 is a drawing Select the 12 third pattern images corresponding to the intermediate value of the focus position from the 55 third pattern images in the second image to perform the first image overlay step to form a reference image; FIG. 4 is based on this specification As shown in an embodiment of FIG. 1, a simplified schematic diagram of a method of calculating the IOU index of a pattern image and a reference image; FIG. 5 is a second overlay step after removing a plurality of erroneous images according to an embodiment of the present specification Implementation method: and FIG. 6 is a plurality of focus-image score relationship curves used to determine the optimal focus position according to an embodiment of the present specification.

101: Perform image capturing steps on at least one tested pattern with a plurality of focus positions to obtain a plurality of pattern images

102: Select a plurality of pattern images corresponding to the intermediate value of the focus position from the plurality of pattern images, and perform the first stacking step to form a plurality of reference images

103: Remove a plurality of error images from the plurality of pattern images based on these reference images

104: Select at least two of the plurality of remaining pattern images corresponding to the intermediate value of the focus position, and perform a second overlay step to form a plurality of standard images

105: According to these standard images, the remaining Perform similarity analysis on pattern images to obtain multiple image scores

106: Use these image scores to determine the best focus position

Claims (10)

A method for optimizing lithography focusing parameters, including: performing a first image capturing step on a first measured pattern at a plurality of focus positions to obtain a plurality of first pattern images; from the first patterns Select a plurality of first pattern images corresponding to an intermediate value of the focus positions from the image, and perform a first overlay step to form a first reference image; based on the first reference image, select the first reference image Remove a plurality of erroneous images from the pattern image; select at least two of the plurality of remaining first pattern images corresponding to the intermediate values of the focus positions, and perform a second overlay step to form a A first standard image; and performing a first similarity analysis on the remaining first pattern images according to the first standard image to obtain a plurality of first image scores, and thereby determine an optimal focus position. The method for optimizing lithographic focusing parameters as described in item 1 of the patent application scope, wherein the first image capturing step includes using a plurality of light energies in combination with the focus positions to capture the first pattern images. The method for optimizing lithographic focusing parameters as described in item 2 of the patent application scope, wherein after removing a plurality of erroneous images from the first pattern images, further includes: selecting more from the remaining first pattern images A first pattern image captured with the same light energy; from the plurality of remaining first pattern images corresponding to the intermediate values of the focus positions, select a plurality of captured images using the same light energy Of the first pattern image, the second image overlay step; and comparing each of the first pattern images captured with the same light energy with the first standard image to obtain the first image scores . The method for optimizing lithographic focusing parameters as described in item 3 of the patent application scope, wherein the step of obtaining the first image scores includes: capturing one of the first pattern images captured at the same focal position A first pixel value group; extract a standard pixel value group of the first standard image; and calculate a correlation coefficient between the first pixel value group and the standard pixel value group. The method for optimizing lithographic focusing parameters as described in item 3 of the patent application scope further includes a noise filtering step before performing the second overlay step. The method for optimizing lithographic focusing parameters as described in item 5 of the patent application scope, wherein the noise filtering step includes using a Gaussian Blur algorithm. The method for optimizing lithographic focusing parameters as described in item 1 of the patent scope further includes: performing a second image capturing step on a second tested pattern with the focus positions to obtain a plurality of second pattern images Selecting a plurality of second pattern image images corresponding to the intermediate values of the focus positions from the second pattern images, and performing a third overlay step to form a second reference image; according to the second A reference image, remove a plurality of erroneous images from the second pattern images; select at least two of the plurality of remaining second pattern images corresponding to the intermediate values of the focal points, and perform a fourth The step of overlaying images to form a second standard image; and performing a second similarity analysis on the remaining second pattern images according to the second standard image to obtain a plurality of second image scores. The method for optimizing lithographic focusing parameters as described in item 7 of the patent application scope, wherein determining the best focus includes: forming a first focus-image score based on the first image scores and the second image scores, respectively A relationship curve and a second focus-image score relationship curve; performing a linear regression on the first focus-image score relationship curve and the second focus-image score relationship curve to obtain a curve of second order); and a derivative of the quadratic curve. The method for optimizing lithographic focusing parameters as described in item 1 of the patent application scope, wherein the step of removing a plurality of erroneous images from the first pattern images includes calculating each of the first image based on the first reference image An IOU (intersection-over-union, IOU) indicator of a pattern image. The method for optimizing lithographic focusing parameters as described in item 1 of the patent scope, wherein the IOU index refers to an image intersection of one of the first pattern images and the first reference image divided by the two Part of the image of the author.

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