Methods for correcting OPC models, methods for fabricating photomasks, and photolithography methods

Abstract

This invention provides a method for correcting an OPC model, a method for fabricating a photomask, and a photolithography method. The OPC model correction method first establishes an initial OPC model; then corrects the initial OPC model to obtain a corrected OPC model, and performs a convergence check on the corrected OPC model until it converges before proceeding to the next step. In the step of correcting the initial OPC model, this invention adjusts the number of corrections based on the convergence of the corrected OPC model, achieving the effect of reducing runtime without affecting the accuracy of the OPC model correction. Specifically, each client layout file corresponds to a different number of OPC model corrections. When the number of corrections for the OPC model is less than the number in the standard file, no extra corrections are needed. When the number of corrections for the OPC model is greater than the number in the standard file, it avoids wasting time running OPCV when the number of corrections is insufficient and the OPC model is not properly corrected.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and in particular to a method for modifying an OPC model, a method for fabricating a photomask, and a photolithography method. Background Technology

[0002] As process nodes continue to shrink, OPC (optical proximity correction) models are an indispensable part of modern semiconductor processes in order to improve process windows and yield. However, simulation calculations of OPC models often involve a lot of resources and time. How to reduce run time without affecting accuracy is a problem that all semiconductor manufacturers need to solve.

[0003] During the development of existing OPC models, the impact of different numbers of corrections on the results is tested. After development, to avoid affecting the performance of subsequent tape-out (the final stage after design completion and preparation for sending data to the manufacturing plant), the recipe is fixed, forming a golden recipe (standard process document). However, after mass production begins, there are hundreds of different customer layout files (DBs) that need to be corrected. Not every customer layout file DB is suitable for the original number of corrections. There is a possibility that the number of corrections may be insufficient, the OPC model may not be properly corrected, and time may be wasted running OPCV (OPC Verification). Summary of the Invention

[0004] The purpose of this invention is to provide a method for correcting an OPC model, a method for creating a photomask, and a photolithography method, in order to solve the problem that the number of corrections in the standard OPC model cannot be fully applied to every customer layout file (DB), which may result in insufficient corrections to the OPC model, incomplete correction of the OPC model, and wasted time running OPC verification.

[0005] To address the aforementioned technical problems, this invention provides a method for modifying an OPC model, comprising:

[0006] Establish the initial OPC model;

[0007] The initial OPC model is modified to obtain a modified OPC model, and the convergence of the modified OPC model is checked until the modified OPC model converges before proceeding to the next step. The number of times the initial OPC model is modified is adjusted according to the convergence check result of the modified OPC model.

[0008] The modified OPC model is verified to check its accuracy. If it meets the standard, a photomask is made using the modified OPC model.

[0009] Optionally, methods for modifying the initial OPC model to obtain a modified OPC model include:

[0010] Step S21: Perform a first correction step on the initial OPC model and check the convergence of the OPC model after the first correction step. If the OPC model after the first correction step converges, the correction of the initial OPC model ends. If the OPC model after the first correction step does not converge, mark the first non-converged region and proceed to step S22.

[0011] Step S22: Perform a second correction step on the first non-converged region of the OPC model after the first correction step and check the convergence of the OPC model after the second correction step. If the OPC model after the second correction step converges, the correction of the OPC model after the first correction step ends. If the OPC model after the second correction step does not converge, mark the second non-converged region and execute step S23.

[0012] Step S23: Perform a third correction step on the second non-converged region of the OPC model after the second correction step and check the convergence of the OPC model after the third correction step. If the OPC model after the third correction step converges, the correction of the OPC model after the second correction step ends. If the OPC model after the third correction step does not converge, continue to mark the third non-converged region and continue to correct the OPC model after the third correction step until the OPC model converges.

[0013] Optionally, the number of corrections to the initial OPC model includes the number of corrections in the first correction step, the number of corrections in the second correction step, and the number of corrections in the third correction step.

[0014] Optionally, the number of corrections in the first correction step, the number of corrections in the second correction step, and the number of corrections in the third correction step shall be at least greater than one.

[0015] Optionally, the number of corrections in the first correction step, the number of corrections in the second correction step, and the number of corrections in the third correction step decrease sequentially.

[0016] Optionally, the method for establishing the initial OPC model includes:

[0017] Obtain the target image;

[0018] The wiring process is performed based on the target pattern to obtain wafer data;

[0019] The wafer data was used for initial OPC modeling.

[0020] Optionally, the steps of performing wiring processes based on the target pattern and obtaining wafer data include:

[0021] Design test patterns and create test masks based on the test patterns;

[0022] The test pattern is transferred to the wafer using the test mask template, an actual pattern is formed on the wafer, and wafer data obtained by testing the actual pattern is acquired.

[0023] Optionally, the method for validating the modified OPC model includes:

[0024] The test graphic is processed using an OPC model to obtain a simulated graphic;

[0025] The simulated graphic is verified; if the verification passes, the simulated graphic is determined to be correct.

[0026] Based on the same inventive concept, the present invention also provides a method for manufacturing a photomask, which uses an OPC model modified by the OPC model correction method described above to obtain a simulated pattern, and transfers the simulated pattern onto the photomask to form a mask pattern.

[0027] Based on the same inventive concept, the present invention also provides a photolithography method, comprising: fabricating a mask pattern using the method for fabricating a photomask as described above, and transferring the mask pattern onto a wafer using an exposure process and a development process to form a photolithographic pattern on the wafer.

[0028] In the OPC model correction method provided by this invention, an initial OPC model is first established; the initial OPC model is corrected to obtain a corrected OPC model, and the convergence of the corrected OPC model is checked until it converges before proceeding to the next step. The number of corrections to the initial OPC model is adjusted based on the convergence check result of the corrected OPC model. The corrected OPC model is then verified to check its accuracy. If it meets the standard, a photomask is fabricated using the corrected OPC model. This invention adjusts the number of corrections based on the convergence of the corrected OPC model in the step of correcting the initial OPC model, achieving the effect of reducing runtime without affecting the accuracy of the OPC model correction. That is, each client layout file (DB) corresponds to a different number of OPC model corrections. When the number of corrections to the OPC model is less than the number of corrections in the fixed file, no extra corrections are needed. When the number of corrections to the OPC model is greater than the number of corrections in the fixed file, the problem of wasting time running OPCV when the number of corrections is insufficient and the OPC model is not properly corrected is avoided. Attached Figure Description

[0029] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention. Wherein:

[0030] Figure 1 This is a flowchart of the OPC model correction method according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of step S20 in the OPC model correction method of this embodiment of the invention. Detailed Implementation

[0032] To make the objectives, advantages, and features of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clarify the explanation of the embodiments of this invention. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and may sometimes use different scales.

[0033] As used in this invention, the singular forms “a,” “an,” and “the” include plural objects; the term “or” is generally used to mean “and / or”; the term “a number” is generally used to mean “at least one”; and the term “at least two” is generally used to mean “two or more”. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature. Additionally, as used in this invention, the placement of one element on another element generally only indicates a connection, coupling, cooperation, or transmission relationship between the two elements, which can be direct or indirect through an intermediate element. It should not be construed as indicating or implying a spatial positional relationship between the two elements, i.e., one element can be located arbitrarily inside, outside, above, below, or to one side of the other element, unless otherwise explicitly stated. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] Figure 1 This is a flowchart of the OPC model modification method according to an embodiment of the present invention. Figure 1 As shown, this embodiment provides a method for correcting an OPC model, including:

[0035] Step S10: Establish the initial OPC model;

[0036] Step S20: Correct the initial OPC model to obtain a corrected OPC model, and perform a convergence check on the corrected OPC model until the corrected OPC model converges before proceeding to the next step. The number of corrections to the initial OPC model is adjusted according to the convergence check result of the corrected OPC model.

[0037] Step S30: Verify the modified OPC model to check its accuracy. If it meets the standard, then use the modified OPC model to create a photomask.

[0038] In step S10, the method for establishing the initial OPC model includes:

[0039] Step S11: Obtain the target graphic;

[0040] Step S12: Perform wiring process according to the target pattern and obtain wafer data;

[0041] Step S13: Initial OPC modeling is performed using the wafer data.

[0042] In step S11, the target graphic is obtained, which is a customer layout file DB (Data Base). After mass production begins, there are hundreds of different customer layout files DB that need to be corrected, and the number of times the OPC model needs to be corrected varies depending on the customer layout file DB.

[0043] In step S12, the steps of performing layout processing based on the target pattern and obtaining wafer data include: designing a test pattern and fabricating a test mask based on the test pattern; transferring the test pattern to the wafer using the test mask to form an actual pattern on the wafer, and obtaining wafer data obtained by testing the actual pattern. Following the routing process, a main or frame layout operation is also included, performing design rule checks such as DRC checks or AG checks.

[0044] In steps S12 and S13, the wafer data includes the linewidth, coordinates, dimensions, and spacing of the pattern. Specifically, the wafer data corresponds to the mask data layout. Multiple wafer data are obtained by collecting experimental data from actual silicon wafers under specific photolithography process conditions. Each wafer data can be obtained through sampling. Typically, a mask data layout has multiple wafer patterns, and each wafer pattern corresponds to one wafer data. It should be noted that one wafer data corresponds to multiple sets of parameters for one wafer pattern. These multiple sets of parameters include, but are not limited to, the linewidth, coordinates, dimensions, and spacing of the pattern.

[0045] Figure 2 This is a schematic diagram of step S20 in the OPC model correction method of this embodiment of the invention. Figure 2 As shown, in step S20, the method for correcting the initial OPC model to obtain the corrected OPC model includes:

[0046] Step S21: Perform a first correction step on the initial OPC model and check the convergence of the OPC model after the first correction step. If the OPC model after the first correction step converges, the correction of the initial OPC model ends. If the OPC model after the first correction step does not converge, mark the first non-converged region and proceed to step S22.

[0047] Step S22: Perform a second correction step on the first non-converged region of the OPC model after the first correction step and check the convergence of the OPC model after the second correction step. If the OPC model after the second correction step converges, the correction of the OPC model after the first correction step ends. If the OPC model after the second correction step does not converge, mark the second non-converged region and execute step S23.

[0048] Step S23: Perform a third correction step on the second non-converged region of the OPC model after the second correction step and check the convergence of the OPC model after the third correction step. If the OPC model after the third correction step converges, the correction of the OPC model after the second correction step ends. If the OPC model after the third correction step does not converge, continue to mark the third non-converged region and continue to correct the OPC model after the third correction step until the OPC model converges.

[0049] The number of corrections to the initial OPC model includes the number of corrections in the first correction step, the second correction step, and the third correction step. Each of these steps has at least one correction. The number of corrections in the first, second, and third steps decreases sequentially. In this embodiment, the number of corrections in the first step is, for example, 4; in the second step, 3; and in the third step, 2. In the prior art, the number of corrections in the OPC model is fixed, for example, 7. Some customer layout files (DB) only require 4 corrections for the OPC model to converge after the first correction step; in this case, the verification step of the OPC model can proceed after the first correction step. Some customer layout files (DB) only require 6 corrections for the OPC model to converge after the second correction step; in this case, the verification step of the OPC model can proceed after the second correction step. For some clients, even after seven revisions to the database (DB), the OPC model has not yet converged. If the OPC model verification step is initiated with a fixed seven revisions for each file, the verification will certainly not meet the standards. In other words, performing the OPC model verification step before the OPC model is properly revised is a waste of time. Those skilled in the art can set the number of revisions in the first revision step, the second revision step, and the third revision step according to the actual situation. This embodiment does not impose any restrictions on this.

[0050] In this embodiment, the number of corrections is adjusted based on the convergence of the corrected OPC model during the step of correcting the initial OPC model. This achieves the effect of reducing runtime without affecting the accuracy of the OPC model correction. Specifically, each client layout file (DB) corresponds to a different number of OPC model corrections. When the number of corrections for the OPC model is less than that in the standard file, no extra corrections are needed. When the number of corrections for the OPC model is greater than that in the standard file, this avoids wasting time running OPCV when the number of corrections is insufficient and the OPC model is not properly corrected.

[0051] In step S30, the method for verifying the modified OPC model includes:

[0052] Step S31: Perform OPC model processing on the test graphic to obtain a simulated graphic;

[0053] Step S32: Verify the simulated graphic; if the verification passes, the simulated graphic is determined to be correct; if the verification fails, the OPC model is re-established.

[0054] This embodiment also provides a method for fabricating a photomask, which uses an OPC model modified by the OPC model correction method described above to obtain a simulated graphic, and then transfers the simulated graphic onto the photomask to form a mask graphic.

[0055] This embodiment also provides a photolithography method, including: fabricating a mask pattern using the method for fabricating a photomask as described above, and transferring the mask pattern onto a wafer using an exposure process and a development process to form a photolithography pattern on the wafer.

[0056] In summary, the OPC model correction method provided in this invention first establishes an initial OPC model; then, it corrects the initial OPC model to obtain a corrected OPC model, and performs a convergence check on the corrected OPC model until it converges before proceeding to the next step. The number of corrections to the initial OPC model is adjusted based on the convergence check result of the corrected OPC model. The corrected OPC model is then verified to check its accuracy. If it meets the standard, a photomask is fabricated using the corrected OPC model. This invention adjusts the number of corrections based on the convergence of the corrected OPC model in the step of correcting the initial OPC model, achieving the effect of reducing runtime without affecting the accuracy of the OPC model correction. That is, each client layout file (DB) corresponds to a different number of OPC model corrections. When the number of corrections to the OPC model is less than the number of corrections in the fixed file, there is no need to correct extra corrections. When the number of corrections to the OPC model is greater than the number of corrections in the fixed file, it avoids wasting time running OPCV when the number of corrections is insufficient and the OPC model is not properly corrected.

[0057] Furthermore, it should be understood that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method of modifying an OPC model, characterized by, The method comprises the following steps: establishing an initial OPC model; correcting the initial OPC model to obtain a corrected OPC model, and performing a convergence check on the corrected OPC model until the corrected OPC model converges and then entering the next step, wherein the number of corrections of the initial OPC model is adjusted according to the convergence check result of the corrected OPC model; verifying the corrected OPC model to check the accuracy of the corrected OPC model, and if the corrected OPC model meets the standard, manufacturing a photomask based on the corrected OPC model; wherein the method for correcting the initial OPC model to obtain a corrected OPC model comprises the following steps: step S21: performing a first correction step on the initial OPC model and checking the convergence of the OPC model after the first correction step, if the OPC model after the first correction step converges, ending the correction of the initial OPC model, if the OPC model after the first correction step does not converge, marking a first non-converged area, and performing step S22; step S22: performing a second correction step on the first non-converged area of the OPC model after the first correction step and checking the convergence of the OPC model after the second correction step, if the OPC model after the second correction step converges, ending the correction of the OPC model after the first correction step, if the OPC model after the second correction step does not converge, marking a second non-converged area, and performing step S23; step S23: performing a third correction step on the second non-converged area of the OPC model after the second correction step and checking the convergence of the OPC model after the third correction step, if the OPC model after the third correction step converges, ending the correction of the OPC model after the second correction step, if the OPC model after the third correction step does not converge, continuing to mark a third non-converged area and continuing to correct the OPC model after the third correction step until the OPC model converges; 2. The method of claim 1, wherein, the number of corrections in the first correction step, the number of corrections in the second correction step and the number of corrections in the third correction step decrease in turn.

3. The method of revising an OPC model according to claim 1 or 2, characterized in that, The number of corrections of the initial OPC model includes the number of corrections in the first correction step, the number of corrections in the second correction step and the number of corrections in the third correction step.

4. The method of claim 1, wherein, The number of corrections in the first correction step, the number of corrections in the second correction step and the number of corrections in the third correction step are at least greater than one. The method for establishing the initial OPC model comprises: obtaining a target pattern; performing a wiring process according to the target pattern and obtaining wafer data; 5. The method of claim 4, wherein, performing initial OPC modeling using the wafer data. The step of performing a wiring process according to the target pattern and obtaining wafer data comprises: designing a test pattern and manufacturing a test mask based on the test pattern; 6. The method of claim 5, wherein, transferring the test pattern to a wafer using the test mask to form an actual pattern on the wafer, and obtaining wafer data obtained by testing the actual pattern. The method for verifying the corrected OPC model comprises: OPC model processing is performed on the test pattern to obtain a simulation pattern; verification is performed on the simulation pattern; if the verification is passed, it is determined that the simulation pattern is correct.

7. A method of making a photomask blank, the method comprising: The simulation pattern is obtained by using the OPC model corrected by the correction method of the OPC model according to claims 1-6, and the simulation pattern is transferred to a photomask to form a mask pattern.

8. A lithographic method, characterized by, comprising: The mask pattern is formed by using the method of claim 7, and the mask pattern is transferred to a wafer by using an exposure process and a development process to form a photolithography pattern on the wafer.

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