A photolithography model construction method, a method for predicting SRAF pattern exposure imaging, and a program product

Abstract

The present application relates to the field of computing lithography, in particular to a kind of photolithography model construction method, comprising the following steps: obtaining the actual exposure imaging result of part SRAF pattern on wafer;Establish initial lithography model, image measurement plane and light intensity threshold are added to initial lithography model as variable;Part SRAF pattern is substituted into initial lithography model to simulate, and based on different image measurement plane and light intensity threshold, the simulation result corresponding to part SRAF pattern is obtained;Compare simulation result with actual exposure imaging result, the image measurement plane and light intensity threshold corresponding to the simulation result with highest similarity are recorded as optimal simulation point;According to optimal simulation point, initial lithography model is calibrated, and prediction lithography model is obtained.The present application also provides a kind of prediction SRAF pattern exposure imaging method and program product, solve the problem that traditional OPC lithography model cannot accurately predict SRAF exposure imaging result.

Description

[Technical Field]

[0001] This invention relates to the field of computational lithography, and particularly to a method for constructing a lithography model, a method and program product for predicting SRAF pattern exposure imaging. [Background Technology]

[0002] Photolithography is a key process in the manufacturing of semiconductor devices, essentially transferring patterns from a photomask onto a silicon wafer. Photomask designs typically include both densely distributed patterns (such as equally spaced lines) and sparse patterns (such as individual lines). The photolithography process window for sparse patterns is significantly smaller than that for densely distributed patterns, thus limiting the overall process window.

[0003] To address this issue, sub-resolution assist features (SRAFs) are typically added around sparse patterns. This makes the sparse patterns appear as dense patterns from an optical perspective, thereby improving the lithography process window. However, as assist patterns, SRAFs should not be used to generate patterns on the wafer. If the SRAF pattern size is small, the improvement in the process window is not significant. If the SRAF pattern size is large, there is a risk of generating sidelobe patterns on the wafer. Sidelobes are considered defects and affect yield. Therefore, choosing the appropriate SRAF is crucial.

[0004] Predicting the exposure imaging of SRAF patterns on wafers can provide important information for selecting the appropriate SRAF.

[0005] Mainstream lithography models based on optical proximity correction (OPC) are typically applicable to the master pattern but not to the SRAF pattern, resulting in inaccurate predictions of SRAF exposure imaging. This is because the feature sizes of the master and SRAF patterns differ significantly. Therefore, a highly accurate lithography model for predicting SRAF exposure imaging on wafers is urgently needed. [Summary of the Invention]

[0006] To address the problem that traditional OPC lithography models cannot accurately predict SRAF exposure imaging results, this invention provides a lithography model construction method, a method for predicting SRAF pattern exposure imaging, and a program product.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for constructing a lithography model, comprising the following steps: obtaining actual exposure imaging results of a portion of SRAF patterns on a wafer; establishing an initial lithography model, adding the image measurement plane and light intensity threshold as variables to the initial lithography model; substituting the portion of the SRAF patterns into the initial lithography model for simulation, and obtaining simulation results corresponding to the portion of the SRAF patterns based on different image measurement planes and light intensity thresholds; comparing the simulation results with the actual exposure imaging results, and recording the image measurement plane and light intensity threshold corresponding to the simulation result with the highest similarity as the optimal simulation point; calibrating the initial lithography model based on the optimal simulation point to obtain a predicted lithography model.

[0008] Preferably, obtaining the simulation results of the partial SRAF pattern under different image measurement planes and light intensity thresholds includes the following steps: constructing a two-dimensional solution space with the image measurement plane and light intensity threshold as the horizontal and vertical coordinates, the two-dimensional solution space including multiple process points, each process point corresponding to an image measurement plane and light intensity threshold; substituting each process point and the partial SRAF pattern into the initial lithography model for simulation solution, obtaining the difference between the light intensity distribution of the exposure image corresponding to the partial SRAF pattern and the light intensity threshold; determining the printing probability of the current SRAF pattern based on the difference between the light intensity distribution of the exposure image and the light intensity threshold.

[0009] Preferably, determining the printing probability of the current SRAF pattern based on the difference between the light intensity distribution of the exposed image and the light intensity threshold includes the following steps: if the difference between the light intensity after exposure and the light intensity threshold is greater than a preset tolerance range, and the light intensity is relatively large, then the printing probability is determined to be high; if the difference between the light intensity after exposure and the light intensity threshold is greater than the preset tolerance range, and the light intensity threshold is relatively large, then the printing probability is determined to be low; if the difference between the light intensity after exposure and the light intensity threshold is less than the preset tolerance range, then the printing probability is determined to be moderate; the printing probability is calculated to be between 0 and 1 based on the magnitude of the difference between the light intensity and the light intensity threshold.

[0010] Preferably, obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer includes the following steps: acquiring a scanning electron microscope (SEM) image of a portion of the SRAF pattern on the wafer; and adding a corresponding imaging status label to each SRAF pattern marker based on whether the SRAF pattern generates a pattern in the SEM image after exposure and whether the generated pattern is continuous.

[0011] Preferably, the SEM images include SEM images exposed under standard and non-standard conditions.

[0012] Preferably, the optical information of the initial lithography model, except for the image measurement plane and the light intensity threshold, is consistent with the lithography model used for the actual exposure of the partial SRAF pattern.

[0013] Preferably, after obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer, the method further includes the following steps: dividing the actual exposure imaging results of the portion of the SRAF pattern on the wafer into a calibration group and a verification group; inputting the calibration group into the initial lithography model for simulation and calibration of the initial lithography model; inputting the verification group into the predictive lithography model to obtain verification simulation results, and comparing the verification simulation results with the actual exposure results to verify the reliability of the predictive lithography model.

[0014] Preferably, if the reliability of the predicted lithography model does not meet the preset requirements, the predicted lithography model is further calibrated according to the inspection group.

[0015] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: A method for predicting SRAF pattern exposure imaging includes the following steps: obtaining a predictive lithography model based on the above-mentioned lithography model construction method; predicting whether other SRAF patterns on the wafer will be printed through the predictive lithography model.

[0016] 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, the steps of the above-mentioned photolithography model construction method are implemented.

[0017] Compared with the prior art, the photolithography model construction method provided by the present invention has the following beneficial effects:

[0018] 1. The lithography model construction method provided in the first embodiment of the present invention includes the following steps: obtaining the actual exposure imaging results of a portion of SRAF patterns on a wafer; establishing an initial lithography model, adding the image measurement plane and light intensity threshold as variables to the initial lithography model; substituting a portion of the SRAF patterns into the initial lithography model for simulation, and obtaining simulation results corresponding to the portion of the SRAF patterns based on different image measurement planes and light intensity thresholds; comparing the simulation results with the actual exposure imaging results, and recording the image measurement plane and light intensity threshold corresponding to the simulation result with the highest similarity as the optimal simulation point; calibrating the initial lithography model based on the optimal simulation point to obtain the predicted lithography model. It can be understood that by recalibrating the image measurement plane and light intensity threshold based on the exposure imaging results of a portion of SRAF patterns on a wafer, a lithography model suitable for SRAF is established. Compared with the traditional OPC lithography model, this method can more accurately predict the exposure imaging results of SRAF patterns, with higher reliability and stronger practicality.

[0019] 2. The lithography model construction method provided in the first embodiment of the present invention obtains the simulation results of a portion of the SRAF pattern under different image measurement planes and light intensity thresholds by including the following steps: constructing a two-dimensional solution space with the image measurement plane and light intensity threshold as the horizontal and vertical coordinates, the two-dimensional solution space including multiple process points, each process point corresponding to an image measurement plane and a light intensity threshold; substituting each process point and a portion of the SRAF pattern into the initial lithography model for simulation and solution, obtaining the difference between the light intensity distribution of the exposure image corresponding to the portion of the SRAF pattern and the light intensity threshold; determining the printing probability of the current SRAF pattern based on the difference between the light intensity distribution of the exposure image and the light intensity threshold. It is understandable that by performing simulation calculations on all process points, it is more beneficial to find the process point that best matches the actual process from a large number of simulation results, making the subsequent model calibration process more reliable.

[0020] 3. In the photolithography model construction method provided in the first embodiment of the present invention, determining the printing probability of the current SRAF pattern based on the difference between the light intensity distribution of the exposed image and the light intensity threshold includes the following steps: if the difference between the light intensity after exposure and the light intensity threshold is greater than a preset tolerance range, and the light intensity is relatively large, then the printing probability is determined to be high; if the difference between the light intensity after exposure and the light intensity threshold is greater than the preset tolerance range, and the light intensity threshold is relatively large, then the printing probability is determined to be low; if the light intensity after exposure is equal to the light intensity threshold, then the printing probability is determined to be moderate; if the difference between the light intensity after exposure and the light intensity threshold is less than the preset tolerance range, then the printing probability is determined to be moderate; the printing probability is calculated to be between 0 and 1 based on the magnitude of the difference between the light intensity and the light intensity threshold. It can be understood that the exposure imaging result of the SRAF pattern at the current process point can be evaluated relatively accurately based on the difference between the light intensity after exposure and the light intensity threshold.

[0021] 4. In the photolithography model construction method provided in the first embodiment of the present invention, obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer includes the following steps: obtaining SEM images of a portion of the SRAF pattern on the wafer; adding corresponding imaging status labels to each SRAF pattern marker based on whether the SRAF pattern generates a pattern in the SEM image after exposure and whether the generated pattern is continuous. It can be understood that adding imaging status labels to the generated pattern based on the SEM image is equivalent to classifying the actual exposure imaging results. The classified actual exposure imaging results are easier to compare with simulation results; it is only necessary to determine whether the simulation result falls into a certain category, without needing to compare them one by one to obtain the optimal simulation point. Therefore, the above method is simple, easy to implement, and highly reliable.

[0022] 5. In the lithography model construction method provided in the first embodiment of the present invention, the SEM images include SEM images exposed under standard conditions and non-standard conditions. Understandably, SEM images under both conditions can provide richer samples for the initial lithography model, improving the accuracy of the calibration model.

[0023] 6. In the lithography model construction method provided in the first embodiment of the present invention, the optical information of the initial lithography model, except for the image measurement plane and the light intensity threshold, is consistent with the lithography model used for the actual exposure of some SRAF patterns. It is understandable that ensuring the consistency of other optical information can maximize the reproduction of the real lithography process, making the simulation results more accurate and the obtained optimal simulation points more practical.

[0024] 7. In the lithography model construction method provided in the first embodiment of the present invention, after obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer, the method further includes the following steps: dividing the actual exposure imaging results of a portion of the SRAF pattern on the wafer into a calibration group and a verification group; inputting the calibration group into the initial lithography model for simulation and calibration of the initial lithography model; inputting the verification group into the predictive lithography model to obtain verification simulation results, and comparing the verification simulation results with the actual exposure results to verify the reliability of the predictive lithography model. It can be understood that the setting of the verification group further verifies the reliability of the predictive lithography model, ensuring reliability during application.

[0025] 8. In the lithography model construction method provided in the first embodiment of the present invention, if the reliability of the predicted lithography model does not meet the preset requirements, the predicted lithography model is further calibrated according to the verification group. Under normal circumstances, the classification of the verification group and the calibration group is uniform, that is, SRAF patterns of different types and positions are evenly divided into the two groups. Normally, the calibration and verification results are basically consistent. In practical applications, if inconsistent results occur, it is because the calibrated model does not cover the types of the verification group. In this case, further calibration of the model using the verification group can ensure the reliability of the model.

[0026] 9. The present invention also provides a method for predicting SRAF pattern exposure imaging, which has the same beneficial effects as the above-mentioned method for constructing a lithography model, and will not be described in detail here.

[0027] 10. This invention also provides a program product that has the same beneficial effects as the above-described photolithography model construction method, which will not be described in detail here. [Attached Image Description]

[0028] Figure 1 This is a flowchart illustrating the photolithography model construction method provided in the first embodiment of the present invention.

[0029] Figure 2This is a schematic diagram of the two-dimensional solution space of the photolithography model construction method provided in the first embodiment of the present invention.

[0030] Figure 3 This is a standard example diagram of label setting for the photolithography model construction method provided in the first embodiment of the present invention.

[0031] Figure 4 This is a comparison chart of the label and P value of each SRAF at the optimal simulation point of the lithography model construction method provided in the first embodiment of the present invention.

[0032] Figure 5 This is a verification result diagram of the inspection group in the photolithography model construction method provided in the first embodiment of the present invention.

[0033] Figure 6 This is a flowchart illustrating the method for predicting SRAF pattern exposure imaging provided in the second embodiment of the present invention.

[0034] Figure 7 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. Photolithography model construction method; 2. Method for predicting SRAF pattern exposure imaging; 3. Program product;

[0037] 30. Computer program instructions.

Detailed Implementation Methods

[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 1 The first embodiment of the present invention provides a method 1 for constructing a lithography model, comprising the following steps: obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer; establishing an initial lithography model, adding the image measurement plane and light intensity threshold as variables to the initial lithography model; substituting a portion of the SRAF pattern into the initial lithography model for simulation, and obtaining the simulation results corresponding to the portion of the SRAF pattern under different image measurement planes and light intensity thresholds based on different image measurement planes and light intensity thresholds; comparing the simulation results with the actual exposure imaging results, and recording the image measurement plane and light intensity threshold corresponding to the simulation result with the highest similarity as the optimal simulation point; calibrating the initial lithography model based on the optimal simulation point to obtain a predicted lithography model.

[0040] Understandably, based on the partial SRAF exposure imaging results on the wafer, the image measurement plane and light intensity threshold of the initial lithography model are recalibrated to establish a lithography model suitable for SRAF. Compared with the traditional OPC lithography model, it can more accurately predict the exposure imaging results of SRAF patterns, with higher reliability and greater practicality.

[0041] Preferably, the initial lithography model, except for the image measurement plane and light intensity threshold, has optical information consistent with the lithography model used in the actual exposure of some SRAF patterns. Understandably, ensuring consistency in other optical information maximizes the reproduction of the real lithography process, making the simulation results more accurate and the obtained optimal simulation points more practical. Specifically, the optical information that maintains consistency includes...

[0042] In some embodiments, obtaining simulation results of partial SRAF graphics under different image measurement planes and light intensity thresholds includes the following steps: constructing a two-dimensional solution space with the image measurement plane and light intensity threshold as the horizontal and vertical axes, such as... Figure 2 As shown, the two-dimensional solution space includes multiple process points, each corresponding to an image measurement plane and a light intensity threshold. Each process point and a portion of the SRAF pattern are substituted into the initial lithography model for simulation and solution, obtaining the difference between the light intensity distribution and the light intensity threshold of the exposure image corresponding to the portion of the SRAF pattern. The printing probability of the current SRAF pattern is determined based on the difference between the light intensity distribution and the light intensity threshold of the exposure image.

[0043] Understandably, simulating all process points makes it easier to identify the process points that best match the actual process from a large number of simulation results, making the subsequent model calibration process more reliable.

[0044] Furthermore, determining the printing probability of the current SRAF pattern based on the difference between the light intensity distribution of the exposed image and the light intensity threshold includes the following steps: if the difference between the light intensity after exposure and the light intensity threshold is greater than a preset tolerance range, and the light intensity is greater than the light intensity threshold, then the printing probability is determined to be high; if the difference between the light intensity after exposure and the light intensity threshold is greater than a preset tolerance range, and the light intensity threshold is greater than the light intensity, then the printing probability is determined to be low; if the difference between the light intensity after exposure and the light intensity threshold is less than a preset tolerance range, then the printing probability is determined to be moderate; the printing probability is calculated to be between 0 and 1 based on the magnitude of the difference between the light intensity and the light intensity threshold.

[0045] Specifically, the P-value represents the printing probability, where P indicates the probability of SRAF imaging simulated by the lithography model, which is affected by two variables: the image measurement plane and the light intensity threshold. When the sidelobe risk is high, the P-value is between 0.5 and 1; when the sidelobe risk is constant, the P-value is approximately 0.5; and when the sidelobe risk is low, the P-value is between 0 and 0.5.

[0046] Understandably, the difference between the light intensity after exposure and the light intensity threshold can be used to evaluate the exposure imaging results of the SRAF pattern at the current process point relatively accurately.

[0047] In some embodiments, obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer includes the following steps: acquiring a SEM image of the portion of the SRAF pattern on the wafer; and adding a corresponding imaging status label to each SRAF pattern marker based on whether the SRAF pattern generates a pattern in the SEM image after exposure and whether the generated pattern is continuous. It can be understood that adding imaging status labels based on the generated pattern from the SEM image is equivalent to classifying the actual exposure imaging results. The classified actual exposure imaging results are easier to compare with simulation results; it is only necessary to determine whether the simulation result falls into a certain category, without needing to compare them one by one to obtain the optimal simulation point. Therefore, the above method is simple, easy to implement, and highly reliable.

[0048] In some embodiments, the imaging status label setting method is as follows:

[0049] If no image is generated after SRAF exposure, its imaging status label is defined as 0.

[0050] If the image exists and is continuous after SRAF exposure, its imaging state label is defined as 1.

[0051] If an image exists but is discontinuous after SRAF exposure, its imaging status label is defined as 0.5. A standard example of label setting is shown below. Figure 3 As shown.

[0052] Furthermore, the SEM images include those exposed under both standard and non-standard conditions. SEM images exposed under standard conditions comprise at least half of the total dataset to ensure that the simulation is primarily conducted under standard conditions. Understandably, SEM images from both conditions provide a richer sample for the initial lithography model, improving the accuracy of the calibration model.

[0053] In some embodiments, after obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer, the method further includes the following steps: dividing the actual exposure imaging results of the portion of the SRAF pattern on the wafer into a calibration group and a verification group; inputting the calibration group into the initial lithography model for simulation and calibration of the initial lithography model; inputting the verification group into the predictive lithography model to obtain verification simulation results, and comparing the verification simulation results with the actual exposure results to verify the reliability of the predictive lithography model. Understandably, the setting of the verification group further verifies the reliability of the predictive lithography model, ensuring reliability during application.

[0054] Furthermore, if the reliability of the predicted lithography model does not meet the preset requirements, the predicted lithography model is further calibrated according to the verification group. Under normal circumstances, the classification of the verification group and the calibration group is uniform, meaning that SRAF patterns of different types and locations are evenly assigned to the two groups. Normally, the calibration and verification results are basically consistent. In practical applications, if inconsistent results occur, it is because the calibrated model does not cover the types of the verification group. In this case, recalibrating the model using the verification group can ensure the model's reliability.

[0055] The photolithography model construction method 1 provided in the first embodiment of this invention will be described below with specific examples:

[0056] 104 SRAF data points were collected from the wafer, including 84 SEM images exposed under standard conditions and 20 SEM images exposed under non-standard conditions. Of these, 27 SRAFs were continuous and present on the wafer after exposure, and their label was set to 1. 38 SRAFs were discontinuous and present on the wafer after exposure, and their label was set to 0.5. 39 SRAFs did not generate an image on the wafer after exposure, and their label was set to 0. The data were randomly divided into two groups: a calibration group with 84 SRAFs and a verification group with 20 SRAFs.

[0057] Based on the OPC software's lithography model, an initial lithography model is established by inputting information on the light source, photomask, and photoresist, with a photoresist thickness of 85nm. The exposure focus is consistent with the main pattern exposure focus and is set at 54nm from the top of the photoresist. The image measurement plane and light intensity threshold are added as variables to the model.

[0058] The image measurement plane is solved within a range of 5 to 85 nm from the top of the photoresist, with a step size of 5 nm. The light intensity threshold is solved within a range of 0.0966 to 0.1.046, with a step size of 0.005.

[0059] The light intensity distribution of the SRAF-exposed image under the solution conditions was calculated. The difference between the peak light intensity and the light intensity threshold was obtained, and the P-value was obtained through S-shaped function mapping. Comparing the simulation results with the actual results, it can be found that when the image measurement plane is 80nm and the light intensity threshold value is 0.0991, the simulation results are closest to the actual results. The label and P-value of SRAF at various locations in the calibration group are as follows. Figure 4 As shown, the p-values ​​of the 53 SRAFs with labels of 0.5 and 1 are all greater than 0.5. Of the 31 SRAFs with a label of 0, 29 have p-values ​​less than 0.5, and 2 have p-values ​​greater than 0.5. Overall, 97.6% of the SRAF simulation results are consistent with reality, with no missed alarms; however, 2.4% of the SRAFs exhibit false alarms.

[0060] The initial lithography model was calibrated using a process point with an image measurement plane of 80nm and a light intensity threshold of 0.0991, resulting in a predicted lithography model. The predicted lithography model was then used to simulate the test group, and the results are as follows: Figure 5 As shown in the figure, the p-values ​​of the 12 SRAFs with labels of 0.5 and 1 are all greater than 0.5. Among the 8 SRAFs with a label of 0, the p-values ​​of 7 SRAFs are less than 0.5, and the p-value of 1 SRAF is greater than 0.5. Based on the verification simulation results, it can be determined that the reliability of the predictive lithography model is relatively high.

[0061] Please see Figure 6 A second embodiment of the present invention provides a method 2 for predicting SRAF pattern exposure imaging, comprising the following steps: obtaining a predictive lithography model according to the lithography model construction method 1 provided in the first embodiment of the present invention; and predicting whether other SRAF patterns on the wafer will be printed using the predictive lithography model. It should be understood that other SRAF patterns refer to SRAF patterns not obtained from the wafer during the construction of the predictive lithography model.

[0062] Please see Figure 7 The third embodiment of the present invention also provides a program product 3, including computer program instructions 30, which, when executed, implement the steps of the photolithography model construction method 1 described above.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 noteworthy 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. Compared with the prior art, the photolithography model construction method provided by this invention has the following beneficial effects:

[0067] 1. The lithography model construction method provided in the first embodiment of the present invention includes the following steps: obtaining the actual exposure imaging results of a portion of SRAF patterns on a wafer; establishing an initial lithography model, adding the image measurement plane and light intensity threshold as variables to the initial lithography model; substituting a portion of the SRAF patterns into the initial lithography model for simulation, and obtaining simulation results corresponding to the portion of the SRAF patterns based on different image measurement planes and light intensity thresholds; comparing the simulation results with the actual exposure imaging results, and recording the image measurement plane and light intensity threshold corresponding to the simulation result with the highest similarity as the optimal simulation point; calibrating the initial lithography model based on the optimal simulation point to obtain the predicted lithography model. It can be understood that by recalibrating the image measurement plane and light intensity threshold based on the exposure imaging results of a portion of SRAF patterns on a wafer, a lithography model suitable for SRAF is established. Compared with the traditional OPC lithography model, this method can more accurately predict the exposure imaging results of SRAF patterns, with higher reliability and stronger practicality.

[0068] 2. The lithography model construction method provided in the first embodiment of the present invention obtains the simulation results of a portion of the SRAF pattern under different image measurement planes and light intensity thresholds by including the following steps: constructing a two-dimensional solution space with the image measurement plane and light intensity threshold as the horizontal and vertical coordinates, the two-dimensional solution space including multiple process points, each process point corresponding to an image measurement plane and a light intensity threshold; substituting each process point and a portion of the SRAF pattern into the initial lithography model for simulation and solution, obtaining the difference between the light intensity distribution of the exposure image corresponding to the portion of the SRAF pattern and the light intensity threshold; determining the printing probability of the current SRAF pattern based on the difference between the light intensity distribution of the exposure image and the light intensity threshold. It is understandable that by performing simulation calculations on all process points, it is more beneficial to find the process point that best matches the actual process from a large number of simulation results, making the subsequent model calibration process more reliable.

[0069] 3. In the photolithography model construction method provided in the first embodiment of the present invention, determining the printing probability of the current SRAF pattern based on the difference between the light intensity distribution of the exposed image and the light intensity threshold includes the following steps: if the difference between the light intensity after exposure and the light intensity threshold is greater than a preset tolerance range, and the light intensity is relatively large, then the printing probability is determined to be high; if the difference between the light intensity after exposure and the light intensity threshold is greater than the preset tolerance range, and the light intensity threshold is relatively large, then the printing probability is determined to be low; if the light intensity after exposure is equal to the light intensity threshold, then the printing probability is determined to be moderate; if the difference between the light intensity after exposure and the light intensity threshold is less than the preset tolerance range, then the printing probability is determined to be moderate; the printing probability is calculated to be between 0 and 1 based on the magnitude of the difference between the light intensity and the light intensity threshold. It can be understood that the exposure imaging result of the SRAF pattern at the current process point can be evaluated relatively accurately based on the difference between the light intensity after exposure and the light intensity threshold.

[0070] 4. In the photolithography model construction method provided in the first embodiment of the present invention, obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer includes the following steps: obtaining SEM images of a portion of the SRAF pattern on the wafer; adding corresponding imaging status labels to each SRAF pattern marker based on whether the SRAF pattern generates a pattern in the SEM image after exposure and whether the generated pattern is continuous. It can be understood that adding imaging status labels to the generated pattern based on the SEM image is equivalent to classifying the actual exposure imaging results. The classified actual exposure imaging results are easier to compare with simulation results; it is only necessary to determine whether the simulation result falls into a certain category, without needing to compare them one by one to obtain the optimal simulation point. Therefore, the above method is simple, easy to implement, and highly reliable.

[0071] 5. In the lithography model construction method provided in the first embodiment of the present invention, the SEM images include SEM images exposed under standard conditions and non-standard conditions. Understandably, SEM images under both conditions can provide richer samples for the initial lithography model, improving the accuracy of the calibration model.

[0072] 6. In the lithography model construction method provided in the first embodiment of the present invention, the optical information of the initial lithography model, except for the image measurement plane and the light intensity threshold, is consistent with the lithography model used for the actual exposure of some SRAF patterns. It is understandable that ensuring the consistency of other optical information can maximize the reproduction of the real lithography process, making the simulation results more accurate and the obtained optimal simulation points more practical.

[0073] 7. In the lithography model construction method provided in the first embodiment of the present invention, after obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer, the method further includes the following steps: dividing the actual exposure imaging results of a portion of the SRAF pattern on the wafer into a calibration group and a verification group; inputting the calibration group into the initial lithography model for simulation and calibration of the initial lithography model; inputting the verification group into the predictive lithography model to obtain verification simulation results, and comparing the verification simulation results with the actual exposure results to verify the reliability of the predictive lithography model. It can be understood that the setting of the verification group further verifies the reliability of the predictive lithography model, ensuring reliability during application.

[0074] 8. In the lithography model construction method provided in the first embodiment of the present invention, if the reliability of the predicted lithography model does not meet the preset requirements, the predicted lithography model is further calibrated according to the verification group. Under normal circumstances, the classification of the verification group and the calibration group is uniform, that is, SRAF patterns of different types and positions are evenly divided into the two groups. Normally, the calibration and verification results are basically consistent. In practical applications, if inconsistent results occur, it is because the calibrated model does not cover the types of the verification group. In this case, further calibration of the model using the verification group can ensure the reliability of the model.

[0075] 9. The present invention also provides a method for predicting SRAF pattern exposure imaging, which has the same beneficial effects as the above-mentioned method for constructing a lithography model, and will not be described in detail here.

[0076] 10. This invention also provides a program product that has the same beneficial effects as the above-described photolithography model construction method, which will not be described in detail here.

[0077] The foregoing has provided a detailed description of a lithography model construction method, a method for predicting SRAF pattern exposure imaging, 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 the 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 constructing a photolithography model, characterized in that: Includes the following steps: Obtain the actual exposure imaging results of a portion of the SRAF pattern on the wafer; An initial lithography model is established, and the image measurement plane and light intensity threshold are added as variables to the initial lithography model; The partial SRAF pattern is substituted into the initial lithography model for simulation, and the simulation results corresponding to the partial SRAF pattern are obtained based on different image measurement planes and light intensity thresholds. The simulation results are compared with the actual exposure imaging results, and the image measurement plane and light intensity threshold corresponding to the simulation result with the highest similarity are recorded as the optimal simulation point. The initial lithography model is calibrated based on the optimal simulation point to obtain the predicted lithography model; Obtaining the simulation results of the aforementioned partial SRAF graphics under different image measurement planes and light intensity thresholds includes the following steps: A two-dimensional solution space is constructed using the image measurement plane and the light intensity threshold as the horizontal and vertical axes. The two-dimensional solution space includes multiple process points, and each process point corresponds to an image measurement plane and a light intensity threshold. Substitute each process point and the partial SRAF pattern into the initial photolithography model for simulation and solution to obtain the difference between the light intensity distribution of the exposure image corresponding to the partial SRAF pattern and the light intensity threshold. The printing probability of the current SRAF pattern is determined based on the difference between the light intensity distribution of the exposed image and the light intensity threshold. The printing probability is calculated to be between 0 and 1 based on the magnitude of the difference between the light intensity and the light intensity threshold. Obtaining the actual exposure imaging results of a portion of the SRAF pattern on the wafer includes the following steps: Obtain a SEM image of the SRAF pattern on the upper part of the wafer; Based on whether the SRAF pattern generates an image in the SEM image after exposure and whether the generated image is continuous, a corresponding imaging status label is added to each SRAF pattern marker: If no image is generated after SRAF exposure, its imaging status label is defined as 0; If the image exists and is continuous after SRAF exposure, its imaging status label is defined as 1; If an image exists but is discontinuous after SRAF exposure, its imaging status label is defined as 0.

5.

2. The photolithography model construction method as described in claim 1, characterized in that: Determining the printing probability of the current SRAF pattern based on the difference between the light intensity distribution of the exposed image and the light intensity threshold includes the following steps: If the difference between the light intensity after exposure and the light intensity threshold is greater than the preset tolerance range, and the light intensity is relatively large, then the probability of printing is considered to be high. If the difference between the light intensity after exposure and the light intensity threshold is greater than the preset tolerance range, and the light intensity threshold is large, then the probability of printing is judged to be low. If the difference between the light intensity after exposure and the light intensity threshold is less than the preset tolerance range, then the printing probability is determined to be moderate.

3. The photolithography model construction method as described in claim 1, characterized in that: The SEM images include SEM images exposed under standard and non-standard conditions.

4. The photolithography model construction method as described in claim 1, characterized in that: The initial lithography model, except for the image measurement plane and light intensity threshold, has the same optical information as the lithography model used for the actual exposure of the SRAF pattern.

5. The photolithography model construction method as described in claim 1, characterized in that: Obtain partial SRAF patterns on the wafer The actual exposure imaging results are followed by the following steps: The actual exposure imaging results of the aforementioned SRAF patterns on the wafer are divided into a calibration group and an inspection group; The calibration group is passed into the initial lithography model for simulation and calibration of the initial lithography model; The test group is input into the predictive lithography model to obtain the test simulation results, and the test simulation results are compared with the results obtained from the predictive lithography model. The actual exposure results are compared to verify the reliability of the predicted lithography model.

6. The photolithography model construction method as described in claim 5, characterized in that: If the reliability of the predicted lithography model does not meet the preset requirements, the predicted lithography model shall be further calibrated according to the inspection group.

7. A method for predicting SRAF pattern exposure imaging, characterized in that: Includes the following steps: A predictive lithography model is obtained according to the lithography model construction method as described in any one of claims 1-6; The predictive lithography model is used to predict whether other SRAF patterns on the wafer will be printed.

8. A program product comprising computer program instructions, characterized in that: When the computer program instructions are executed, they implement the steps of the photolithography model construction method as described in any one of claims 1-6.

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