A method of screening overlay marks, readable storage medium and program product

Abstract

The present application relates to the field of computing lithography, in particular to a kind of overlay mark screening method, readable storage medium and program product, overlay mark screening method includes the following steps: obtaining the characteristic parameter of overlay mark to be screened;Obtain the optical parameter of overlay measurement, and establish optical model according to optical parameter;Characteristic parameter is brought into optical model and at least two overlay errors in the preset range are set, and then the asymmetry result of overlay mark to be screened is simulated and calculated;Overlay error and asymmetry result are calculated by linear fitting, and fitting result is obtained;According to fitting result, overlay mark to be screened is screened.The overlay mark screening method provided by the present application can screen out overlay mark prone to larger measurement error.

Description

Technical Field

[0001] This invention relates to the field of computational lithography, and particularly to a method for screening overlay marks, a readable storage medium, and a program product. Background Technology

[0002] In integrated circuit manufacturing, overlay represents the alignment relationship between two process layers, requiring an overlay error of less than one-third of the critical dimension. As photolithography process nodes continue to advance and critical dimensions shrink, the requirements for overlay error become increasingly stringent. In the photolithography process, overlay error is controlled through real-time measurement and feedback. Accurate measurement of overlay error is a fundamental prerequisite for overlay error control.

[0003] The robustness and sensitivity of overlay measurement results are closely related to the characteristics of the overlay marks, and the design of the overlay marks is the foundation for accurate measurement of overlay errors. In the actual screening process, it is necessary to perform simulation calculations on a large number of overlay marks with different characteristics, sort them according to the simulation calculation results, and select the overlay marks that can meet the process requirements.

[0004] The simulation results represent relevant indicators for overlay measurement. For example, the k-value represents the sensitivity of the measurement results to changes in overlay error. However, current overlay mark screening indicators, represented by k, cannot identify overlay marks that are prone to causing large measurement errors. Summary of the Invention

[0005] To address the problem that traditional methods cannot identify overlay marks that can easily cause significant measurement errors, this invention provides a method for screening overlay marks, a readable storage medium, and a program product.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for screening overprinted marks, the method comprising the following steps: obtaining feature parameters of the overprinted marks to be screened; obtaining optical parameters of overprinting measurement, and establishing an optical model based on the optical parameters; substituting the feature parameters into the optical model and setting at least two overprinting errors within a preset range, and then simulating and calculating the asymmetry result of the overprinted marks to be screened; performing linear fitting calculation on the overprinting errors and the asymmetry result to obtain a fitting result; and screening the overprinted marks to be screened based on the fitting result.

[0007] Preferably, the fitting result includes the ratio of the intercept to the slope of the fitted line and / or the correlation index of the fitted line.

[0008] Preferably, the number of overlay errors is two.

[0009] Preferably, the screening of the overprinted marks to be screened based on the fitting results includes the following steps: when the number of overprinting errors is two, the overprinted marks to be screened are screened based on the ratio of the intercept to the slope of the fitted line; when the number of overprinting errors is greater than two, the overprinted marks to be screened are screened based on the correlation index of the fitted line and / or the ratio of the intercept to the slope.

[0010] Preferably, when the ratio of the intercept to the slope of the fitted line is greater than a preset first threshold and / or the correlation index is less than a preset second threshold, the overlay mark corresponding to the fitted line is selected.

[0011] Preferably, the preset range is 0~40nm.

[0012] Preferably, the overlay error and the asymmetry result are fitted with a straight line to obtain the following linear equation:

[0013] Asy = slope*overlay + intercept;

[0014] Where Asy represents the asymmetry result, overlay represents the set overlay error, and slope and intercept correspond to the slope and intercept of the fitted line, respectively.

[0015] Preferably, the feature parameters include film thickness, film material, pattern size, pattern parameters, and segmentation parameters; the optical parameters include light source type, wavelength, and other parameters.

[0016] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a readable storage medium storing computer program instructions thereon, wherein when the computer program instructions are executed, the steps of the screening method for overlay markings as described above are implemented.

[0017] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a program product, including computer program instructions, wherein when the computer program instructions are executed, they implement the steps of the method described above.

[0018] Compared with the prior art, the screening method for overlay marks provided by the present invention has the following beneficial effects:

[0019] 1. The first embodiment of the present invention provides a method for screening overlay marks, comprising the following steps: obtaining characteristic parameters of the overlay marks to be screened; obtaining optical parameters for overlay measurement and establishing an optical model based on the optical parameters; inputting the characteristic parameters into the optical model and setting at least two overlay errors within a preset range, and then simulating and calculating the asymmetry result of the overlay marks to be screened; performing linear fitting calculation between the overlay error and the asymmetry result to obtain the fitting result; and screening the overlay marks to be screened based on the fitting result. It can be understood that the asymmetry result of the overlay marks can be used to reflect the overlay error generated by the overlay marks during the exposure process. By performing linear fitting between the asymmetry result and the overlay error, the fitting result can be used to determine which overlay marks are prone to large measurement errors under preset process conditions. It should be understood that compared to the actual exposure process, the fitting condition can be considered ideal. If some overlay marks can be fitted and calculated to have large measurement errors under ideal conditions, then they are more likely to have large measurement errors in the actual process. As can be seen, the overlay mark screening method provided in the first embodiment of the present invention screens overlay marks that are prone to large measurement errors during the actual exposure process by means of linear fitting. On the one hand, it eliminates the need to determine which overlay marks will produce large measurement errors after exposure through the actual exposure process, thereby improving the yield rate of the process and reducing costs. On the other hand, the method can screen a large number of overlay marks in a short time, thereby improving the efficiency of the process.

[0020] 2. In the first embodiment of the present invention, a method for screening overlay marks is provided. The fitting result includes the ratio of the intercept to the slope of the fitted straight line and / or the correlation index of the fitted straight line. It should be understood that the correlation index and the ratio of the intercept to the slope of the fitted straight line are both related to the calculation error. The calculation error corresponds to the measurement error in the actual process flow. The larger the correlation index, the smaller the calculation error; the smaller the ratio of the intercept to the slope, the smaller the calculation error. It can be seen that the calculation error is positively or negatively correlated with the correlation index and the ratio of the intercept to the slope of the fitted straight line. The magnitude of the calculation error can be determined by evaluating these two indicators.

[0021] 3. In the first embodiment of the present invention, a screening method for overlay marks is provided, wherein the number of overlay errors is two. It should be understood that fitting a straight line requires at least two points. The more points fitted, the more accurate the fitted line will be. However, this will also increase the time of the fitting simulation process. Therefore, setting only two overlay errors can shorten the simulation process time and improve the screening efficiency while ensuring the fitting conditions.

[0022] 4. The first embodiment of the present invention provides a method for screening overlay marks. The screening of overlay marks based on the fitting results includes the following steps: when the number of overlay errors is two, the overlay marks are screened based on the ratio of the intercept to the slope of the fitted line; when the number of overlay errors is greater than two, the overlay marks are screened based on the correlation index of the fitted line and / or the ratio of the intercept to the slope. It can be understood that the larger the correlation index of the fitted line, the smaller the calculation error; the smaller the ratio of the intercept to the slope of the fitted line, the smaller the calculation error. When fitting is performed using only two points, evaluating the correlation index of the line is meaningless; therefore, the magnitude of the calculation error is determined solely by evaluating the ratio of the intercept to the slope. When the number of overlay errors exceeds two, the calculation error can be evaluated using both the correlation index and the ratio of the intercept to the slope. Therefore, the above method is more flexible and practical.

[0023] 5. In the first embodiment of the present invention, a method for screening overlay marks is provided. When the ratio of the intercept to the slope of the fitted straight line is greater than a preset first threshold and / or the correlation index is less than a preset second threshold, the overlay marks corresponding to the fitted straight line are screened out. It is understood that the purpose of the overlay mark screening method provided in the first embodiment of the present invention is to screen out overlay marks that are prone to large measurement errors. However, the evaluation criteria for the magnitude of measurement errors may not be the same in different process flows. Therefore, the screening criteria can be flexibly adjusted using preset first and second thresholds to meet the screening tasks under different process flows.

[0024] 6. In the first embodiment of the present invention, a screening method for overlay marks is provided, wherein the preset range is 0~40nm. It is understood that a large range of overlay errors is not likely to occur in actual production and would waste unnecessary computing resources. Based on production experience, setting the preset range of overlay errors within 0~40nm saves computing resources while also covering most of the overlay errors that are likely to occur in actual production.

[0025] 7. The second embodiment of the present invention also provides a readable storage medium, which has the same beneficial effects as the screening method of the overprinted mark described above, and will not be repeated here.

[0026] 8. The third embodiment of the present invention also provides a program product that has the same beneficial effects as the screening method of the above-described overlay mark, and will not be described again here. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the screening method for overprinted marks provided in the first embodiment of the present invention.

[0028] Figure 2This is a schematic diagram illustrating the correspondence between the intercept / slope of different marker fittings and the overlay error provided in the first embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram illustrating the correspondence between different marker linear fitting correlation indices and overlay calculation errors provided in the first embodiment of the present invention.

[0030] Figure 4 This is a schematic diagram of the steps for screening overprinted marks to be screened, provided in the first embodiment of the present invention.

[0031] Figure 5 This is a schematic diagram of the features of a one-dimensional overlay mark provided in the first embodiment of the present invention.

[0032] Figure 6 This is a schematic diagram showing the correspondence between the asymmetry of overlay marks with different features and the set overlay value provided in the first embodiment of the present invention.

[0033] Figure 7 This is a schematic diagram of the structure of a readable storage medium provided in the second embodiment of the present invention.

[0034] Figure 8 This is a schematic diagram of the structure of the program product provided in the third embodiment of the present invention.

[0035] Explanation of reference numerals in the attached diagram:

[0036] 1. A method for filtering overprinted marks; 2. A readable storage medium; 3. A program product;

[0037] 20. Computer program instructions; 30. Computer program instructions. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] Please see Figure 1The first embodiment of the present invention provides a method 1 for screening overprinted marks, comprising the following steps: obtaining characteristic parameters of the overprinted marks to be screened; obtaining optical parameters of overprinting measurement, and establishing an optical model based on the optical parameters. It should be understood that the optical parameters of overprinting measurement are some set parameters measured in the actual process, which are used as simulation parameters to establish the optical model (the optical parameters can be manually input or imported from a preset database); inputting the characteristic parameters into the optical model and setting at least two overprinting errors within a preset range, and then simulating and calculating the asymmetry result of the overprinted marks to be screened; performing linear fitting calculation on the overprinting error and the asymmetry result to obtain the fitting result; and screening the overprinted marks to be screened based on the fitting result.

[0040] Understandably, the asymmetry of overlay marks can be used to reflect the overlay error generated during the exposure process. By fitting the asymmetry result with the overlay error using a straight line, it is possible to determine which overlay marks are prone to large measurement errors under preset process conditions. It should be understood that the fitting condition is an ideal condition compared to the actual exposure process. If some overlay marks can be fitted and calculated to have large measurement errors under ideal conditions, then they are more likely to have large measurement errors in the actual process. Therefore, the overlay mark screening method 1 provided in the first embodiment of the present invention screens overlay marks that are prone to large measurement errors in the actual exposure process by using a straight line fitting method. On the one hand, it eliminates the need to determine which overlay marks will produce large measurement errors after exposure through the actual exposure process, thus improving the yield rate of the process and reducing costs. On the other hand, this method can screen a large number of overlay marks in a short time, improving the efficiency of the process flow.

[0041] It should be understood that the criterion for determining a large measurement error can be determined based on the number of simulation results. When the number of simulation results is large, the identifiable error value can be smaller, and vice versa.

[0042] In some embodiments, the feature parameters include film thickness, film material, pattern size, pattern parameters, and segmentation parameters; as shown in Table 1:

[0043]

[0044] Table 1 Overlay Marking Settings

[0045] Optical parameters include light source type, wavelength, and other parameters, as shown in Table 2:

[0046]

[0047] Table 2 Range of measured light parameters

[0048] Furthermore, some parameters with minor impact on simulation calculations in Tables 1 and 2 were omitted, such as the film layer parameters with overlay markings. The main selection was based on graphic parameters with graphic layers, as shown in Table 3:

[0049]

[0050] Table 3

[0051] Furthermore, the asymmetry result is the difference in intensity between the positive and negative first-order diffraction beams. Understandably, the overlay error and the difference in intensity between the positive and negative first-order diffraction beams have a linear relationship within a certain process range. This certain process range refers to a tolerable measurement range.

[0052] For example, calculating the intensity difference between the positive and negative first-order diffraction light includes the following steps:

[0053] Set the overlay mark parameters and the measured light parameters (as shown in Table 3);

[0054] The overlay marking features are input into a model with preset optical parameters to calculate the spectra of different diffraction orders;

[0055] The obtained spectra of different diffraction orders are converted into intensities, and the intensity difference between the positive and negative first-order diffraction light is calculated.

[0056] Please combine Figure 2 and Figure 3 In some embodiments, the fitting results include the ratio of the intercept to the slope of the fitted line (Intercept / Slope) and / or the correlation index of the fitted line. It should be understood that both the correlation index and the intercept / slope ratio of the fitted line are related to the overlay error, which corresponds to the measurement error in the actual process flow. A larger correlation index indicates a smaller overlay error; a smaller intercept / slope ratio indicates a smaller overlay error. Therefore, the overlay error is positively or negatively correlated with the correlation index and the intercept / slope ratio of the fitted line, and the magnitude of the overlay error can be determined by evaluating these two indicators.

[0057] In some embodiments, the overlay error and the asymmetry result are fitted with a straight line to obtain the following linear equation:

[0058] Asy = slope*overlay + intercept

[0059] Where Asy represents the asymmetry result (i.e., the difference in intensity between the positive and negative first-order diffraction light), overlay represents the set overlay error, and slope and intercept correspond to the slope and intercept of the fitted line, respectively.

[0060] The correlation index is calculated as follows:

[0061] R-squared value = regression sum of squares / total sum of squares;

[0062] Where: Regression sum of squares = Total sum of squares - Residual sum of squares;

[0063] Total sum of squares = Sum of squares of the actual values ​​of y;

[0064] Assume the actual measured value is The values ​​calculated from the fitted curves are respectively ,but

[0065] Sum of squared residuals: ;

[0066] Total sum of squares: ;

[0067] = ;

[0068] This is the correlation indicator.

[0069] Please see Figure 4 In some embodiments, the screening of overlay marks to be screened based on the fitting results includes the following steps: determining the number of overlay errors; when the number of overlay errors is two, screening the overlay marks to be screened based on the ratio of the intercept to the slope of the fitted line; when the number of overlay errors is more than two, screening the overlay marks to be screened based on the correlation index of the fitted line and / or the ratio of the intercept to the slope.

[0070] Understandably, the higher the correlation index of the fitted line, the smaller the calculation error; the smaller the ratio of the intercept to the slope of the fitted line, the smaller the calculation error. When fitting using only two points, evaluating the correlation index of the fitted line is meaningless because the correlation index is 1. In this case, the calculation error is judged solely by evaluating the ratio of the intercept to the slope. When the number of overlay errors exceeds two, the calculation error can be evaluated using both the correlation index and the ratio of the intercept to the slope. Therefore, the above methods for evaluating calculation errors are more flexible and practical.

[0071] Furthermore, the number of overlay errors is two. It should be understood that fitting a straight line requires at least two points; the more points used for fitting, the more accurate the fitted line, but this also increases the simulation time. Preferably, the number of overlay errors is two. Setting only two overlay errors can shorten the simulation time and improve the efficiency of the selection process while ensuring the fitting conditions.

[0072] In some embodiments, when the ratio of the intercept to the slope of the fitted straight line is greater than a preset first threshold and / or the correlation index is less than a preset second threshold, the overlay marks corresponding to the fitted straight line are selected. The selected overlay marks are those that are prone to causing large measurement errors in actual production. It is understood that the purpose of the overlay mark selection method 1 provided in the first embodiment of the present invention is to select overlay marks that are prone to causing large measurement errors. However, the evaluation criteria for the magnitude of measurement errors may not be the same in different process flows. Therefore, the selection criteria can be flexibly adjusted using preset first and second thresholds to meet the selection tasks under different process flows.

[0073] Further, the range of the first threshold is 2~5nm, and the range of the second threshold is 0.9~0.99; preferably, the first threshold is 2~3nm, and the range of the second threshold is 0.94~0.96; specifically, the first threshold is 2nm, and the second threshold is 0.95.

[0074] In some embodiments, the preset range of overlay error is 0~40nm. Understandably, a large range of overlay errors is not likely to occur in actual production. Setting an excessively large range would waste unnecessary computing resources. Based on production experience, setting the preset range of overlay error within 0~40nm saves computing resources while also covering most of the overlay errors that are likely to occur in actual production.

[0075] For example, please combine Figure 5 and Figure 6 One-dimensional overlay marks with different features were screened using screening method 1, and the simulation results are as follows: Figure 6 As shown, the overlay error of the overlay mark with a large calculation error exhibits a non-linear characteristic with the result of asymmetric fitting; the overlay error of the overlay mark with a small calculation error shows a linear relationship with the result of asymmetric fitting, and the intercept is small.

[0076] Simulation results show that setting multiple correlation indices between overlay errors and asymmetry for linear fitting can accurately identify most overlay marks with large measurement errors. In the linear fitting of two-point overlay errors, the ratio of intercept to slope can accurately identify overlay marks with large measurement errors. Furthermore, both methods rarely produce false positives.

[0077] Please see Figure 7 The second embodiment of the present invention provides a readable storage medium 2, on which computer program instructions 20 are stored, and when the computer program instructions 20 are executed, the steps of the above-described screening method 1 for overlay marks are implemented.

[0078] Please see Figure 8The third embodiment of the present invention provides a program product 3, which includes computer program instructions 30. When the computer program instructions 30 are executed, they implement the steps of the above-described screening method 1 for overlay marks.

[0079] In the embodiments provided by this invention, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0080] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of the invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Those skilled in the art should also recognize that the embodiments described in the specification are optional embodiments, and the actions and modules involved are not necessarily essential to the invention.

[0081] In various embodiments of the present invention, it should be understood that the sequence number of each process does not necessarily imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0082] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It is particularly important to note that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0083] Compared with the prior art, the screening method for overlay marks provided by the present invention has the following beneficial effects:

[0084] 1. The first embodiment of the present invention provides a method for screening overlay marks, comprising the following steps: obtaining characteristic parameters of the overlay marks to be screened; obtaining optical parameters for overlay measurement and establishing an optical model based on the optical parameters; inputting the characteristic parameters into the optical model and setting at least two overlay errors within a preset range, and then simulating and calculating the asymmetry result of the overlay marks to be screened; performing linear fitting calculation between the overlay error and the asymmetry result to obtain the fitting result; and screening the overlay marks to be screened based on the fitting result. It can be understood that the asymmetry result of the overlay marks can be used to reflect the overlay error generated by the overlay marks during the exposure process. By performing linear fitting between the asymmetry result and the overlay error, the fitting result can be used to determine which overlay marks are prone to large measurement errors under preset process conditions. It should be understood that compared to the actual exposure process, the fitting condition can be considered ideal. If some overlay marks can be fitted and calculated to have large measurement errors under ideal conditions, then they are more likely to have large measurement errors in the actual process. As can be seen, the overlay mark screening method provided in the first embodiment of the present invention screens overlay marks that are prone to large measurement errors during the actual exposure process by means of linear fitting. On the one hand, it eliminates the need to determine which overlay marks will produce large measurement errors after exposure through the actual exposure process, thereby improving the yield rate of the process and reducing costs. On the other hand, the method can screen a large number of overlay marks in a short time, thereby improving the efficiency of the process.

[0085] 2. In the first embodiment of the present invention, a method for screening overlay marks is provided. The fitting result includes the ratio of the intercept to the slope of the fitted straight line and / or the correlation index of the fitted straight line. It should be understood that the correlation index and the ratio of the intercept to the slope of the fitted straight line are both related to the calculation error. The calculation error corresponds to the measurement error in the actual process flow. The larger the correlation index, the smaller the calculation error; the smaller the ratio of the intercept to the slope, the smaller the calculation error. It can be seen that the calculation error is positively or negatively correlated with the correlation index and the ratio of the intercept to the slope of the fitted straight line. The magnitude of the calculation error can be determined by evaluating these two indicators.

[0086] 3. In the first embodiment of the present invention, a screening method for overlay marks is provided, wherein the number of overlay errors is two. It should be understood that fitting a straight line requires at least two points. The more points fitted, the more accurate the fitted line will be. However, this will also increase the time of the fitting simulation process. Therefore, setting only two overlay errors can shorten the simulation process time and improve the screening efficiency while ensuring the fitting conditions.

[0087] 4. The first embodiment of the present invention provides a method for screening overlay marks. The screening of overlay marks based on the fitting results includes the following steps: when the number of overlay errors is two, the overlay marks are screened based on the ratio of the intercept to the slope of the fitted line; when the number of overlay errors is greater than two, the overlay marks are screened based on the correlation index of the fitted line and / or the ratio of the intercept to the slope. It can be understood that the larger the correlation index of the fitted line, the smaller the calculation error; the smaller the ratio of the intercept to the slope of the fitted line, the smaller the calculation error. When fitting is performed using only two points, evaluating the correlation index of the line is meaningless; therefore, the magnitude of the calculation error is determined solely by evaluating the ratio of the intercept to the slope. When the number of overlay errors exceeds two, the calculation error can be evaluated using both the correlation index and the ratio of the intercept to the slope. Therefore, the above method is more flexible and practical.

[0088] 5. In the first embodiment of the present invention, a method for screening overlay marks is provided. When the ratio of the intercept to the slope of the fitted straight line is greater than a preset first threshold and / or the correlation index is less than a preset second threshold, the overlay marks corresponding to the fitted straight line are screened out. It is understood that the purpose of the overlay mark screening method provided in the first embodiment of the present invention is to screen out overlay marks that are prone to large measurement errors. However, the evaluation criteria for the magnitude of measurement errors may not be the same in different process flows. Therefore, the screening criteria can be flexibly adjusted using preset first and second thresholds to meet the screening tasks under different process flows.

[0089] 6. In the first embodiment of the present invention, a screening method for overlay marks is provided, wherein the preset range is 0~40nm. It is understood that a large range of overlay errors is not likely to occur in actual production and would waste unnecessary computing resources. Based on production experience, setting the preset range of overlay errors within 0~40nm saves computing resources while also covering most of the overlay errors that are likely to occur in actual production.

[0090] 7. The second embodiment of the present invention also provides a readable storage medium, which has the same beneficial effects as the screening method of the overprinted mark described above, and will not be repeated here.

[0091] 8. The third embodiment of the present invention also provides a program product that has the same beneficial effects as the screening method of the above-described overlay mark, and will not be described again here.

[0092] The foregoing has provided a detailed description of a screening method for overlay marks, a readable storage medium, and a program product disclosed in the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent substitutions, and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for screening overprinted marks, characterized in that: The method for filtering overprinted marks includes the following steps: Obtain the feature parameters of the overprinted marks to be screened; Obtain the optical parameters required for overlay measurement, and establish an optical model based on the optical parameters; Substitute the characteristic parameters into the optical model and set at least two overlay errors within a preset range, then simulate and calculate the asymmetry result of the overlay mark to be screened; The overlay error and the asymmetry result are fitted with a straight line to obtain the fitting result; The overlay marks to be screened are screened based on the fitting results; The fitting results include the ratio of the intercept to the slope of the fitted line and / or the correlation index of the fitted line.

2. The screening method for overlay marks as described in claim 1, characterized in that: The number of overlay errors is two.

3. The screening method for overlay marks as described in claim 1, characterized in that: The process of filtering the overlay marks to be screened based on the fitting results includes the following steps: When there are two overlay errors, the overlay marks to be screened are screened according to the ratio of the intercept to the slope of the fitted straight line. When the number of overprinting errors is greater than two, the overprinting marks to be screened are screened based on the correlation index of the fitted straight line and / or the ratio of intercept to slope.

4. The screening method for overlay marks as described in claim 3, characterized in that: When the ratio of the intercept to the slope of the fitted line is greater than a preset first threshold and / or the correlation index is less than a preset second threshold, the overlay mark corresponding to the fitted line is selected.

5. The screening method for overlay marks as described in claim 1, characterized in that: The preset range is 0~40nm.

6. The screening method for overlay marks as described in claim 1, characterized in that: The following linear equation is obtained by performing a linear fitting calculation between the overlay error and the asymmetry result: Asy = slope*overlay + intercept; Where Asy represents the asymmetry result, overlay represents the set overlay error, and slope and intercept correspond to the slope and intercept of the fitted line, respectively.

7. The screening method for overlay marks as described in claim 1, characterized in that: The characteristic parameters include film thickness, film material, pattern size, pattern parameters, and segmentation parameters; the optical parameters include light source type, wavelength, numerical aperture (NA), wavelength sampling distance, and Sigma sampling distance.

8. A readable storage medium having computer program instructions stored thereon, characterized in that: When the computer program instructions are executed, they implement the steps of the screening method for overlay marks as described in any one of claims 1-7.

9. A program product comprising computer program instructions, characterized in that: When the computer program instructions are executed, they implement the steps of the method as described in any one of claims 1-7.

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