A method, device and computer equipment for calculating a focus point of a lithography beam

Abstract

The application relates to the field of photoetching technology, in particular to a method and device for calculating a focus point of a photoetching light beam and a computer device, the method comprises the following steps: S0, acquiring a critical dimension of a mask pattern; S1, establishing a focus depth model according to the critical dimension and a preset optical modeling model; S2, under a preset metrology level, bringing the critical dimension into the focus depth model, and calculating a focus point offset of the critical dimension and feature information through a preset first algorithm; and S3, calculating a final focus point of the critical dimension through a preset second algorithm according to the focus point offset and the feature information. The method provided by the application considers the focus point offset and the focus depth information, and can more accurately find the focus point of the photoetching light beam.

Description

Technical Field

[0001] This invention relates to the field of photolithography, and particularly to a method, apparatus, and computer device for calculating the focal point of a photolithography beam. Background Technology

[0002] With the development of photolithography technology, the size of devices in integrated circuit manufacturing has evolved from submicron to ultra-deep submicron. In semiconductor fabrication, photolithography equipment projects a beam of light through a photomask and optical lenses, exposing the circuit pattern onto a silicon wafer with a photosensitive coating. Trenches are formed by etching the exposed or unexposed areas, followed by deposition, etching, and doping to create circuits of different materials. As process nodes in integrated circuit manufacturing continue to advance and feature sizes continue to shrink, accurately finding the focal point of the photolithography beam for exposure imaging becomes crucial. Current photolithography optical modeling does not take into account the focal displacement and depth of focus changes that occur during beam transmission, making it difficult to correct lithography errors caused by beam deviation, resulting in insufficient beam focus accuracy. Summary of the Invention

[0003] To address the technical problem of insufficient precision in existing beam focus, this invention provides a method, apparatus, and computer device for calculating the focus of a lithographic beam.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for calculating the focus of a lithographic beam, comprising the following steps: S0: obtaining the key dimensions of a mask pattern; S1: establishing a depth-of-focus model based on the key dimensions and a preset optical modeling model; S2: at a preset metrological level, inputting the key dimensions into the depth-of-focus model, and calculating the focus offset and feature information of the key dimensions using a preset first algorithm; S3: calculating the final focus of the key dimensions based on the focus offset and feature information.

[0005] Preferably, the critical dimensions include multi-state critical dimensions and single-state critical dimensions.

[0006] Preferably, in step S2, the focus offset of the multi-state key dimension and the feature information of the multi-state key dimension and the single-state key dimension are calculated by a preset first algorithm.

[0007] Preferably, calculating the focus offset of the multi-state key dimension using a preset first algorithm includes the following steps:

[0008] S21: Under a preset measurement level, the parameters of a multi-state key dimension under different states are input into the depth of focus model, and simulation calculation is performed within a preset imaging point range to obtain the CD value corresponding to the multi-state key dimension within the preset imaging point range. The CD is used to describe the image sharpness.

[0009] S22: Based on the CD value corresponding to the multi-state key size within the preset imaging point range, establish offset fitting quadratic curves for different states on a fitting coordinate system established with the imaging point and CD value as coordinate axes, and obtain the fitting focus and fitting weight.

[0010] S23: Under a preset measurement level, the fitting focus and fitting weight are used to obtain the focus offset of the multi-state key dimensions through a weighted average algorithm.

[0011] Preferably, calculating the focus offset of the multi-state key dimension includes the following steps: S24: Determine whether there are any multi-state key dimensions whose focus offset has not yet been calculated. If so, calculate it through the above steps and perform a weighted average calculation on the results calculated for all multi-state key dimensions to obtain the focus offset. If not, obtain the focus offset directly.

[0012] Preferably, the feature information includes optimal focus and depth of focus.

[0013] Preferably, calculating the feature information includes the following steps:

[0014] S26: Input the parameters of the multi-state key dimension and the single-state key dimension in the same state into the depth of focus model, and perform simulation calculation within the preset imaging point range to obtain the CD value of each key dimension within the preset imaging point range.

[0015] S27: Based on the CD value of each of the key dimensions within the preset imaging point range, establish a focal depth fitting quadratic curve on the fitting coordinate system established with the imaging point and CD value as coordinate axes, and obtain the focal depth of each of the key dimensions in the same state.

[0016] S28: Using the focal depth as a reference, the key dimensions are filtered according to preset filtering conditions to obtain the filtered key dimensions;

[0017] S29: Combine the selected key dimensions with the data of the corresponding fitted quadratic curve to obtain the optimal focus at the preset measurement level.

[0018] Preferably, the preset screening conditions include:

[0019] Arrange the critical dimensions in descending order of the depth of focus, and delete the last 40% to 60% of the critical dimensions in the sequence.

[0020] Preferably, when calculating the optimal focus, dimensions with a CD value greater than a preset value are not included in the calculation.

[0021] Preferably, the focus offset and the optimal focus are used to obtain the final focus at a preset measurement level.

[0022] Preferably, the method further includes the following step: S4: verifying the optical error of the final focus.

[0023] Preferably, verifying the optical error of the final focus includes the following steps:

[0024] S40: Provide an initial focus. Under a preset measurement level, incorporate the key dimensions and the initial focus into the optical modeling model to obtain the initial optical error.

[0025] S41: Under a preset measurement level, the key dimensions and the final focus are incorporated into the optical modeling model to obtain optimized optical errors;

[0026] S42: Compare the initial optical error with the optimized optical error to draw a conclusion.

[0027] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: an apparatus for implementing the above method, the apparatus comprising:

[0028] Input module: Used to obtain key dimensions of the mask graphic;

[0029] Modeling module: Used to create a depth-of-focus model based on key dimensions and preset optical modeling models;

[0030] Calculation module: used to calculate focus offset, feature information, and final focus.

[0031] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a computer device, the computer device including a memory, a processor and a computer program stored in the memory, the processor executing the computer program to implement the above-mentioned method.

[0032] Compared with the prior art, the method, apparatus, and computer equipment for calculating the focal point of a photolithographic beam provided by the present invention have the following beneficial effects:

[0033] 1. The method provided in this embodiment of the invention includes the following steps: S0: obtaining the key dimensions of the mask pattern; S1: establishing a depth-of-focus model based on the key dimensions and a preset optical modeling model; S2: at a preset metrological level, inputting the key dimensions into the depth-of-focus model, and calculating the focal offset and feature information of the key dimensions using a preset first algorithm; S3: calculating the final focal point of the key dimensions based on the focal offset and feature information. Existing lithography optical modeling does not take into account the focal displacement and depth-of-focus changes generated by the beam during transmission, making it difficult to correct lithography errors caused by beam offset. The method provided in this embodiment of the invention further refines the focal point calculation by combining the focal offset and feature information of the key dimensions, making the focal point calculation results more accurate, thereby better optimizing the computational lithography effect.

[0034] 2. The key dimensions of the method provided in this embodiment of the invention include multi-state key dimensions and single-state key dimensions. In step S2, the focus offset of the multi-state key dimensions and the feature information of the multi-state key dimensions and single-state key dimensions are calculated by a preset first algorithm. By separating the multi-state key dimensions from the single-state key dimensions and calculating them separately according to their characteristics, the optical error of the final focus is reduced, and the reliability of the final focus is improved.

[0035] 3. The method provided in this embodiment of the invention for calculating the focal offset of the multi-state key dimension using a preset first algorithm includes the following steps: S20: Establishing a fitted coordinate system with the imaging point and CD value as coordinate axes; S21: Substituting the parameters of a multi-state key dimension under different states into the depth-of-focus model, and performing simulation calculations within a preset imaging point range to obtain the CD value corresponding to the multi-state key dimension within the preset imaging point range; S22: Establishing offset fitting quadratic curves under different states on the fitted coordinate system based on the multi-state key dimension within the preset imaging point range and the corresponding CD value, and giving the following definition:

[0036]

[0037]

[0038] In the formula, focus is the fitting focus, weight is the weight, and a and b represent the quadratic and linear coefficients of the offset fitting quadratic curve corresponding to a certain multi-state key dimension in a certain state, respectively; S23: The preset first algorithm is a weighted average algorithm. Under the preset measurement level, the fitting focus and fitting weight are substituted into the following formula for calculation:

[0039]

[0040] In the formula, focus shift is the focus offset, focus and weight are the fitted focus and weight of a certain multi-state dimension in different states, and N is the total number of quadratic curves fitted to the offset of the multi-state key dimension in different states; S24: Determine whether there are any multi-state key dimensions whose focus offset has not yet been calculated. If so, calculate it through the above steps, and perform a weighted average of the results calculated for all multi-state key dimensions to obtain the focus offset. If not, obtain the focus offset directly. It can be seen that the focus offset generated by the multi-state key dimensions after the beam passes through the lens can be fitted and calculated through the above steps, which is of great significance for the error correction of the final focus and further improves the accuracy of the final focus.

[0041] 4. The feature information of the method provided in this embodiment includes optimal focus and depth of focus. Optimal focus is an intermediate quantity for calculating the final focus, that is, the optimal focus that theoretically does not produce focus shift, and it has important reference significance for the calculation process. Depth of focus, on the other hand, measures the importance of each critical dimension on the mask pattern in the current state, and its weight can be interpreted. Depth of focus can evaluate the critical dimensions involved in the calculation of optimal focus. Therefore, the innovative introduction of the concepts of optimal focus and depth of focus into the method provided in this embodiment is one of the inventive points of this invention, and considering the influence of depth of focus makes the error of the calculated final focus smaller.

[0042] 5. The method for calculating feature information provided in this embodiment of the invention includes the following steps: S25: Establishing a fitting coordinate system with imaging points and CD values ​​as coordinate axes; S26: Under a preset measurement level, inputting the parameters of the multi-state key dimensions and single-state key dimensions in the same state into the depth-of-focus model, and performing simulation calculations within a preset imaging point range to obtain the CD value of each key dimension within the preset imaging point range; S27: Based on the CD value of each key dimension within the preset imaging point range, establishing a depth-of-focus fitting quadratic curve corresponding to each key dimension on the fitting coordinate system; S28: Calculating the depth-of-focus of each key dimension in the same state by inputting the data of the depth-of-focus fitting quadratic curve into the following formula:

[0043] dof=g(|a|)

[0044] In the formula, dof is the depth of focus, and a is the coefficient of the quadratic term of each depth-of-focus fitted quadratic curve; using the depth of focus as a reference, the key dimensions are screened according to preset screening conditions to obtain the screened key dimensions; S29: Substitute the data of the fitted quadratic curve corresponding to the screened key dimensions into the following formula for calculation to obtain the optimal focus at the preset measurement level:

[0045]

[0046] In the formula, best focus is the optimal focus, weight and focus represent the weight and fitted focus of all the key dimensions in the same state, respectively, and N is the total number of key dimensions involved in the calculation.

[0047] 6. The preset screening conditions in the method provided in this embodiment of the invention include: arranging the key dimensions in descending order of their depth of focus, and deleting the last 40% to 60% of the key dimensions in the sequence. Screening out key dimensions with larger depth of focus can reduce the influence of key dimensions with smaller depth of focus (i.e., those relatively unfavorable to exposure) on the focal point, thereby increasing the proportion of key dimensions with larger depth of focus in determining the optimal focal point calculation, resulting in a lower optical error in the final focal point of the key dimensions of the mask pattern at a certain measurement level.

[0048] 7. In the method provided in this embodiment of the invention, after establishing the offset fitting quadratic curve and the depth-of-focus fitting quadratic curve, the erroneous dimensions are identified according to a preset standard. When calculating the optimal focus, the erroneous dimensions are not included in the calculation. Therefore, this step eliminates the influence of invalid dimensions measured during the measurement of critical dimensions on the calculation, further improving the accuracy of the optimal focus and reducing the optical error of the optimal focus.

[0049] 8. In the method provided in this embodiment of the invention, the focus offset and the optimal focus are substituted into the following formula for calculation to obtain the final focus at a preset measurement level:

[0050] final focus=best focus±focus shift

[0051] In the formula, "final focus" refers to the final focal point. The above formula incorporates the resulting focus offset into the calculation process, making the calculated final focus closer to the true focal point.

[0052] 9. The method provided in the embodiments of the present invention further includes the following steps:

[0053] S4: Verify the optical error of the final focus. Verifying the optical error of the calculated final focus further demonstrates the method's optimization after taking focus shift and depth of focus into account, showcasing the reliability of the method provided in this embodiment of the invention compared to traditional methods.

[0054] 10. A second embodiment of the present invention also provides an apparatus for implementing the above method, which has the same beneficial effects as the above method for calculating the focal point of a photolithographic beam, and will not be described in detail here.

[0055] 11. A third embodiment of the present invention also provides a computer device, which includes a memory, a processor, and a computer program stored in the memory. The processor executes the method for calculating the focal point of a lithographic beam as described in any of the above embodiments, and has the same beneficial effects as the above-described method for calculating the focal point of a lithographic beam, which will not be described in detail here. Attached Figure Description

[0056] Figure 1 This is a flowchart illustrating the method provided in the first embodiment of the present invention. Figure 1 .

[0057] Figure 2 This is a flowchart illustrating the process of calculating the focus offset of a multi-state critical dimension using the method provided in the first embodiment of the present invention.

[0058] Figure 3 This is a flowchart illustrating the calculation of feature information using the method provided in the first embodiment of the present invention.

[0059] Figure 4 This is a flowchart illustrating the method provided in the first embodiment of the present invention. Figure 2 .

[0060] Figure 5 This is a schematic diagram comparing the differences in RMS calculated by the optical modeling model and the depth-of-focus model provided in the first embodiment of the present invention under different metrological levels.

[0061] Figure 6 This is a schematic diagram of the device provided in the second embodiment of the present invention.

[0062] Figure 7 This is a schematic diagram of the structure of a computer device provided in the third embodiment of the present invention.

[0063] Explanation of reference numerals in the attached diagram:

[0064] 1. Method; 2. Apparatus; 3. Computer equipment. Detailed Implementation

[0065] 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.

[0066] Please see Figure 1The first embodiment of this invention provides a method 1 for calculating the focus of a lithographic beam. Method 1 includes the following steps: S0: obtaining the key dimensions of a mask pattern; S1: establishing a depth-of-focus model based on the key dimensions and a preset optical modeling model; S2: at a preset metrological level, incorporating the key dimensions into the depth-of-focus model, and calculating the focus offset and feature information of the key dimensions using a preset first algorithm; S3: calculating the final focus of the key dimensions based on the focus offset and feature information. Existing lithographic optical modeling does not take into account the focus displacement and depth-of-focus changes generated by the beam during transmission, making it difficult to correct lithographic errors caused by beam offset. The method 1 provided by this embodiment of the invention further refines the focus calculation by combining the focus offset and feature information of the key dimensions, making the focus calculation results more accurate, and thus better optimizing the calculated lithography effect.

[0067] It should be understood that different metrology levels refer to measurements taken at different thicknesses of photoresist when measuring critical dimensions, and model fitting refers to fitting and simulating the target parameters at different thicknesses of photoresist.

[0068] In some embodiments, the critical dimensions include multi-state critical dimensions and single-state critical dimensions. In step S2, the focal offset of the multi-state critical dimensions and the feature information of the multi-state and single-state critical dimensions are calculated using a preset first algorithm. It should be understood that the focal offset refers to the slight deviation of the light beam during photolithography, which can lead to process errors. By separating the multi-state and single-state critical dimensions and calculating them separately based on their characteristics, and by incorporating the focal offset into the calculation of the final focal point, the optical error of the final focal point is reduced, and the reliability of the final focal point is improved.

[0069] Please see Figure 2 In some embodiments, calculating the focus offset of a multi-state key dimension using a preset first algorithm includes the following steps: S21: Under a preset measurement level, the parameters of a multi-state key dimension in different states are input into the depth-of-focus model, and simulation calculations are performed within a preset imaging point range to obtain the CD value corresponding to the multi-state key dimension within the preset imaging point range, where the CD is used to describe image sharpness; S22: Based on the CD value corresponding to the multi-state key dimension within the preset imaging point range, a quadratic curve of offset fitting for different states is established on a fitting coordinate system with the imaging point and CD value as coordinate axes to obtain the fitted focus and fitting weight. The following definitions are given:

[0070]

[0071]

[0072] In the formula, focus is the fitting focus, weight is the weight, and the value of weight is related to a. a and b represent the quadratic and linear coefficients of the offset fitting quadratic curve corresponding to a certain multi-state key dimension in a certain state, respectively. Table i below shows a and b of the offset fitting quadratic curve in different states. It should be understood that one state of the multi-state key dimension corresponds to one offset fitting quadratic curve, and multiple states result in multiple offset fitting quadratic curves; S23: Under a preset measurement level, the fitting focus and fitting weight are used to obtain the focus offset of the multi-state key dimension through a weighted average algorithm:

[0073]

[0074] In the formula, focus shift is the focus offset, focus and weight are the fitted focus and weight of a multi-state dimension in different states, N is the total number of quadratic curves fitted to the offset of the multi-state key dimension in different states, and Standard focus is the focus of the quadratic curve fitted to the offset of the multi-state key dimension in the standard state; S24: Determine if there are any multi-state key dimensions whose focus offset has not yet been calculated. If so, calculate it through the above steps, and perform a weighted average of the results calculated for all multi-state key dimensions to obtain the focus offset. If not, obtain the focus offset directly. It can be seen that the above steps can fit and calculate the focus offset of the multi-state key dimensions after the beam passes through the lens, which is of great significance for the error correction of the final focus and further improves the accuracy of the final focus.

[0075] In some embodiments, the feature information of Method 1 includes optimal focus and depth of focus. Optimal focus is an intermediate quantity for calculating the final focus, that is, the optimal focus that theoretically does not produce focus shift, and it has important reference significance for the calculation process. Depth of focus, on the other hand, measures the importance of each critical dimension on the mask pattern in the current state, i.e., the degree of influence of defocus error on image sharpness. If the image changes very little with the amount of defocus, then a larger depth of focus is more beneficial for exposure. The weights can be interpreted through depth of focus, and it can also evaluate the critical dimensions involved in the optimal focus calculation. Therefore, the innovative introduction of the concepts of optimal focus and depth of focus into Method 1 provided by this embodiment is one of the inventive points of this invention, as considering the influence of depth of focus makes the error between the calculated final focus and the true optimal focus smaller.

[0076] Please see Figure 3In some embodiments, calculating feature information includes the following steps: S26: Substituting the parameters of multi-state key dimensions and single-state key dimensions in the same state into the depth-of-focus model, and performing simulation calculations within a preset imaging point range to obtain the CD value of each key dimension within the preset imaging point range. It should be understood that the same state of multi-state key dimensions and single-state key dimensions is the standard state; S27: Based on the CD value of each key dimension within the preset imaging point range, establishing a depth-of-focus fitting quadratic curve on a fitting coordinate system established with the imaging point and CD value as coordinate axes to obtain the depth of focus of each key dimension in the same state, as defined below:

[0077]

[0078] In the formula, dof represents the depth of focus, and a represents the coefficient of the quadratic term of each depth-of-focus fitted quadratic curve. Using the depth of focus as a benchmark, key dimensions are screened according to preset screening criteria to obtain the screened key dimensions. S28: Using the depth of focus as a benchmark, key dimensions are screened according to preset screening criteria to obtain the screened key dimensions. S29: Substituting the data from the fitted quadratic curves corresponding to the screened key dimensions into the following formula for calculation, the optimal focus at the preset measurement level is obtained.

[0079]

[0080] In the formula, best focus is the optimal focus, weight and focus represent the weight and fitted focus of all key dimensions in the same state, i.e., the standard state, respectively, and N is the total number of key dimensions involved in the calculation.

[0081] In some embodiments, the preset screening criteria include: sorting the key dimensions in descending order of depth of focus, and deleting the last 40% to 60% of the key dimensions in the sequence. Screening out key dimensions with larger depths of focus can reduce the influence of key dimensions with smaller depths of focus, i.e., those relatively unfavorable to exposure, on the focus, thereby increasing the proportion of key dimensions with larger depths of focus in determining the optimal focus calculation, resulting in a lower optical error in the final focus of the key dimensions on the mask pattern at a certain measurement level.

[0082] In some embodiments, after establishing the offset fitting quadratic curve and the depth-of-focus fitting quadratic curve, the erroneous dimensions are identified according to a preset standard. These erroneous dimensions are not included in the calculation of the optimal focus. Therefore, this step eliminates the influence of invalid dimensions measured during the measurement of critical dimensions on the calculation, further improving the accuracy of the optimal focus and reducing the optical error of the optimal focus.

[0083] Understandably, the preset standard for judging erroneous dimensions is the standard CD value. When the peak of the fitted quadratic curve exceeds the standard CD value, the dimension corresponding to the standard state or process window state of the curve is judged as an erroneous dimension.

[0084] In some embodiments, the focus offset and the optimal focus are substituted into the following formula to calculate the final focus at a preset metering level:

[0085]

[0086] In the formula, "final focus" refers to the final focal point. It should be understood that the + / - sign in the formula is determined by the optical error generated by the calculated final focus. If a + sign indicates a smaller calculated optical error, then a + sign is used, and vice versa. The above formula incorporates the resulting focal point shift into the calculation process, resulting in a final focus that is closer to the true focal point.

[0087] Please see Figure 4 In some embodiments, method 1 further includes the following steps:

[0088] S4: Verify the optical error of the final focus. Verifying the optical error of the calculated final focus further demonstrates the degree of optimization of Method 1 after taking focus offset and depth of focus into account, compared with the traditional Method 1, and reflects the reliability of Method 1 provided by the embodiments of the present invention.

[0089] In some embodiments, S4 further includes the following step: S40: Calculate the final focal position at different metering levels using a depth-of-focus model;

[0090] S41: Calculate the optical error of the final focal position at each measurement level using the depth-of-focus model;

[0091] S42: Compare the optical errors of the optical modeling model and the depth-of-focus model.

[0092] It should be understood that the optical error between the optical modeling model and the depth-of-focus model in S42 is the fitted optical error, calculated by the following formula:

[0093]

[0094] Where RMS is the fitting optical error, the definitions of parameters a and b are the same as the definition of focus, and c represents the constant term of the quadratic curve of the depth of focus fitting under standard conditions for different key dimensions.

[0095] As an example, this embodiment first obtains 628 key dimensions for the 28nm node, including 1 multi-state key dimension and 627 single-state key dimensions;

[0096] Establish a depth-of-focus model based on key dimensions and a pre-defined optical modeling model;

[0097] The final focal point and depth of focus under different metrological levels were calculated based on the above formula and focal depth model fitting. The calculation results are shown in Table 1.

[0098] MP 25 30 35 40 45 50 55 60 65 Final focus 32.51 35.44 37.09 38.00 38.65 39.70 41.62 44.98 50.45 dof 22.68 22.60 22.57 22.46 22.27 22.08 22.17 22.19 22.67

[0099] Table 1. Final focus and depth of focus information under different measurement levels (MP) of the depth of focus model.

[0100] Continue to calculate the optical error (RMS) of the final focus at each measurement level (MP) according to the above formula. The calculation results are shown in Table 2.

[0101] MP 25 30 35 40 45 50 55 60 65 70 Final focus 32.51 35.44 37.09 38.00 38.65 39.70 41.62 44.98 50.45 58.04 rms 1.79 1.80 1.81 1.81 1.80 1.76 1.71 1.66 1.68 1.75

[0102] Table 2 Final focal position and optical error under different metrological levels of the depth-of-focus model.

[0103] By inputting the final focal position under different metrological levels into the optical modeling model, the optical error of the final focal position under different metrological levels of the optical modeling model is obtained, and compared with the optical error of the depth-of-focus model, such as... Figure 5 As shown, under the same metrological level, the optical error (RMS) of the depth-of-focus model is significantly smaller than that of the optical modeling model. This indicates that the depth-of-focus model, after incorporating focus shift and depth of focus (dof), is closer to the real focus than the final focus fitted by the optical modeling model, has smaller optical error, and exhibits better optical characteristics during the photolithography process.

[0104] Please see Figure 6 The second embodiment of the present invention also provides an apparatus 2 for implementing the above method 1, comprising: an input module for acquiring key dimensions of a mask pattern;

[0105] Modeling module: Used to create a depth-of-focus model based on key dimensions and preset optical modeling models;

[0106] Calculation module: used to calculate focus offset, feature information, and final focus.

[0107] Please see Figure 7 The third embodiment of the present invention also provides a computer device 3, which includes a memory, a processor, and a computer program stored in the memory. The processor executes the computer program to implement the method 1 described above.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] The foregoing has provided a detailed description of a method, apparatus, and computer device for calculating the focus of a lithographic beam, as 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 embodiments above 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 calculating the focal point of a photolithographic beam, characterized in that: Includes the following steps: S0: Obtain the key dimensions of the mask pattern; S1: Establish a depth-of-focus model based on the key dimensions and the preset optical modeling model; S2: Under a preset measurement level, the key dimension is input into the depth-of-focus model, and the focus offset and feature information of the key dimension are calculated using a preset first algorithm; S3: Calculate the final focus of the key dimension based on the focus offset and feature information; The key dimensions include multi-state key dimensions and single-state key dimensions. In step S2, the focus offset of the multi-state key dimensions and the feature information of the multi-state key dimensions and single-state key dimensions are calculated by a preset first algorithm. Calculating the focus offset of the multi-state key dimensions using a preset first algorithm includes the following steps: S21: Under a preset measurement level, the parameters of a multi-state key dimension under different states are input into the depth of focus model, and simulation calculation is performed within a preset imaging point range to obtain the CD value corresponding to the multi-state key dimension within the preset imaging point range. The CD is used to describe the image sharpness. S22: Based on the CD value corresponding to the multi-state key size within the preset imaging point range, establish offset fitting quadratic curves for different states on a fitting coordinate system established with the imaging point and CD value as coordinate axes, and obtain the fitting focus and fitting weight. S23: Under a preset measurement level, the fitting focus and fitting weight are used to obtain the focus offset of the multi-state key dimensions through a weighted average algorithm; The feature information includes optimal focus and depth of focus; The focus offset and the optimal focus are then substituted into the following formula to calculate the final focus at the preset measurement level: ； Where finalfocus is the final focus, bestfocus is the best focus, and focusshift is the focus offset; Calculating the feature information includes the following steps: S26: Input the parameters of the multi-state key dimension and the single-state key dimension in the same state into the depth of focus model, and perform simulation calculation within the preset imaging point range to obtain the CD value of each key dimension within the preset imaging point range. S27: Based on the CD value of each of the key dimensions within the preset imaging point range, establish a focal depth fitting quadratic curve on the fitting coordinate system established with the imaging point and CD value as coordinate axes, and obtain the focal depth of each of the key dimensions in the same state. S28: Using the focal depth as a reference, the key dimensions are filtered according to preset filtering conditions to obtain the filtered key dimensions; S29: Substitute the data of the fitted quadratic curve corresponding to the selected key dimensions into the following formula for calculation to obtain the optimal focus at the preset measurement level: ； Where bestfocus is the optimal focus, weight and focus represent the weight and fit focus of all key dimensions in the same state, i.e., the standard state, respectively, and N is the total number of key dimensions involved in the calculation.

2. The method as described in claim 1, characterized in that: Calculating the focus offset of the multi-state key dimension includes the following steps: S24: Determine if there are any multi-state key dimensions for which the focus offset has not yet been calculated. If so, perform the calculation through the above steps and calculate the weighted average of the results calculated for all multi-state key dimensions to obtain the focus offset. If not, obtain the focus offset directly.

3. The method as described in claim 1, characterized in that: The preset filtering conditions include: Arrange the critical dimensions in descending order of the depth of focus, and delete the last 40% to 60% of the critical dimensions in the sequence.

4. The method as described in claim 1, characterized in that: When calculating the optimal focus, dimensions with a CD value greater than a preset value are not included in the calculation.

5. The method as described in claim 1, characterized in that: The method further includes the following steps: S4: Verify the optical error of the final focus.

6. The method as described in claim 5, characterized in that: Verifying the optical error of the final focus includes the following steps: S40: Provide an initial focus. Under a preset measurement level, incorporate the key dimensions and the initial focus into the optical modeling model to obtain the initial optical error. S41: Under a preset measurement level, the key dimensions and the final focus are incorporated into the optical modeling model to obtain optimized optical errors; S42: Compare the initial optical error with the optimized optical error to draw a conclusion.

7. An apparatus for calculating the focal point of a lithographic beam, used to implement the method for calculating the focal point of a lithographic beam as described in any one of claims 1-6, characterized in that: The device includes: Input module: Used to obtain key dimensions of the mask graphic; Modeling module: Used to create a depth-of-focus model based on key dimensions and preset optical modeling models; Calculation module: used to calculate focus offset, feature information, and final focus.

8. A computer device, characterized in that: The computer device includes a memory, a processor, and a computer program stored in the memory, the processor executing the computer program to implement the method as described in any one of claims 1-6.

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