Risk prediction and optimization method of SRAF

Abstract

The present invention discloses a risk prediction and optimization method for SRAF, comprising: step 1, designing a series of first test pattern structures, including a first dense pattern area, a spacing area, and a second dense pattern area, wherein the width of the spacing area gradually changes. Step 2, inserting SRAF in the spacing area of ​​each first test pattern structure and performing OPC correction. Step 3, simulating the simulation contour map of each first test pattern structure using an OPC result check program. Step 4, performing risk judgment, comprising: if the simulation contour map does not include the contour map of the SRAF, then verifying that the result is safe. If the simulation contour map includes the contour map of the SRAF, then verifying that the result is unsafe, and going to step 5; step 5, optimizing the parameters of the SRAF with unsafe parameters, and then going to step 2. The present invention can accurately verify the parameter security of the SRAF in various environments in advance and optimize the parameters of the unsafe SRAF, thereby ensuring the safety of inserting the SRAF in the product layout.

Description

Technical Field

[0001] The present invention relates to a semiconductor integrated circuit manufacturing method, and in particular to a risk prediction and optimization method for a sub-resolution-assistance-feature (SRAF). Background Art

[0002] As technology nodes continue to decrease, SRAFs are often added to improve lithography resolution, pattern depth of focus (DOF), and process windows for semi-dense and isolated (iso) patterns. Generally, when using SRAF patterns to optimize the entire process, it is required that the SRAF pattern on the mask cannot be displayed during the entire exposure process to avoid defects that affect product yield. Therefore, it is particularly important to verify the safety of SRAF addition rules in advance.

[0003] At present, the addition of SRAF to the linear layout is mainly based on the rule-based insertion technology. The various parameters of the SRAF inserted by Rule-based are mainly related to the spacing (space) between the two graphics (patterns), that is, the addition rules of SRAFs in the same space are the same without special processing, that is, when the space is the same, the various parameters of the inserted SRAFs are also the same. However, the different patterns corresponding to the two sides of the space have a very large difference in the optical impact on the SRAF. Graphics with a strong optical impact on the SRAF may cause the SRAF to be exposed during the exposure process, causing defects and affecting the product yield. At present, the rules for adding SRAF are mainly gradually expanded through the design of the space cycle (Pitch), such as Figure 2 The grating structure shown is used to screen various SRAF parameters. Since the grating structure with gradually expanded spatial period does not have the greatest impact on the optical properties of SRAF, the selected SRAF rules cannot be fully applicable to layouts in different environments. In particular, for customer layouts with complex environments, the selected SRAF addition rules will cause extra printing in the entire customer layout, requiring subsequent optimization of the SRAF in risky environments. Figure 1 As shown, it is a flow chart of the existing method of inserting SRAF in the layout, including the steps:

[0004] Step S101: Design a series of test pattern (TP) structures on the test mask. Figure 2The illustrated grating structure, with a gradually expanding spatial period, serves as a pattern structure for screening SRAF parameters. The pattern structure, similar to the grating structure, includes patterns 101 and spacers 102. Patterns 101 and spacers 102 are arranged alternately, with SRAF 103 disposed within spacers 102. Pattern 101 has a line width, or width W. The sum of the width W of pattern 101 and the width of spacers 102 is the spatial period P.

[0005] Step S102 , screening out SRAF rules corresponding to different spaces and detecting (checking) the light intensity threshold (Ith) of SRAF extraprinting.

[0006] The SRAF rule corresponding to different spaces is selected by using Figure 2 Carry out, forming different space corresponding Figure 2 ,Simulation can determine whether SRAF is safe, and thus determine the parameters of SRAF.

[0007] Generally, Ith represents the minimum light intensity during extra printing when SRAF forms an extra development. After being projected onto the photoresist through the mask, if the light intensity in the photoresist in the SRAF projection area is greater than Ith, the photoresist will be exposed, and the SRAF pattern will be transferred to the photoresist. This is not allowed, so safety verification is required to ensure that the maximum light intensity corresponding to SRAF is reduced to below Ith.

[0008] Step S103: Add the filtered SRAF to the customer layout.

[0009] However, due to the complex customer layout environment and the presence of SRAF extraprinting, the following step S104 is required.

[0010] Step S104: Debug the SRAF extraprintings one by one to eliminate the SRAF extraprintings.

[0011] Obviously, this one-by-one debugging will reduce efficiency and may result in omissions. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide a SRAF risk prediction and optimization method, which can accurately verify the parameter security of SRAF in various environments in advance and optimize the parameters of unsafe SRAF, thereby ensuring the safety of inserting SRAF in the layout corresponding to the product and reducing the risk of SRAF being exposed and developed.

[0013] To solve the above technical problems, the present invention provides a risk prediction and optimization method for SRAF, which includes the following steps:

[0014] Step 1: Design a series of first test pattern structures, each of which includes a first dense pattern area, a gap area, and a second dense pattern area. Dense lines (DLs) are provided in the first dense pattern area and the second dense pattern area, and the width of the gap area of ​​each first test pattern structure gradually changes.

[0015] A series of the first test pattern structures are used to simulate different environments in which the SRAF is inserted, and the dense pattern is used to enhance the optical impact on the SRAF under different environments.

[0016] Step 2: inserting SRAF into the spacer area of ​​each of the first test pattern structures and performing OPC correction on each of the first test pattern structures after the SRAF is inserted.

[0017] Step 3: Utilize an OPC result checking program to simulate the contour of each of the first test pattern structures.

[0018] Step 4: Conduct risk assessment, including:

[0019] If the simulation contour graph does not include the contour graph of the SRAF, the verification result is that the parameters of the SRAF are safe.

[0020] If the simulation contour graph includes the contour graph of the SRAF, the verification result is that the parameters of the SRAF are unsafe, and the process goes to step 5;

[0021] Step 5: Optimize the parameters of the SRAFs that are unsafe, then go to step 2, and repeat steps 2 to 4 or steps 2 to 5 until the parameters of the SRAFs are safe.

[0022] A further improvement is that after step 2 and before step 4, the following is also included:

[0023] Step 6: Use the OPC optical model to simulate the maximum light intensity value of the SRAF in each of the first test pattern structures.

[0024] A further improvement is that, in step 1, the line width and space period of the dense pattern are set according to the line width and minimum space period allowed in the design rules of the corresponding key layer.

[0025] A further improvement is that, in step 2, the SRAF is inserted using a rule-based technique.

[0026] A further improvement is that the width of the spacer of each first test pattern structure is determined according to the number of inserted SRAFs, and the width of the spacer of each first test pattern structure is gradually changed by gradually changing the number of inserted SRAFs.

[0027] A further improvement is that in step one, the spatial period of the dense pattern is set to be greater than or equal to the minimum spatial period and less than or equal to the first width of the spacing area, and the first width is the width of the spacing area of ​​the first test pattern structure when one SRAF is inserted.

[0028] A further improvement is that, in step 1, in a series of the first test pattern structures, the number of the SRAFs gradually changes from 1 to 6.

[0029] A further improvement is that, when a plurality of SRAFs are provided in the spacer area of ​​the first test pattern structure, in step six, the maximum light intensity value is the maximum light intensity value of all the SRAFs in the spacer area of ​​the first test pattern structure.

[0030] A further improvement is that, in step 2, an OPC optical model with an established process window is used to perform the OPC correction.

[0031] A further improvement is that, in step three, the OPC result checking program simulates a simulation profile of each of the first test pattern structures according to the process window and light intensity threshold of the OPC model.

[0032] A further improvement is that the risk assessment in step 4 further includes:

[0033] comparing the maximum light intensity value of the SRAF in each of the first test pattern structures with a light intensity threshold; if the maximum light intensity value of the SRAF is less than the light intensity threshold, a theoretical judgment result is that the parameters of the SRAF are safe;

[0034] If the maximum light intensity value of the SRAF is greater than or equal to the light intensity threshold, the theoretical judgment result is that the parameters of the SRAF are unsafe, and the process goes to step 5;

[0035] The theoretical judgment result and the verification result complement each other.

[0036] A further improvement is that the light intensity threshold adopts the minimum light intensity value required for SRAF exposure and development verified in the early stage.

[0037] A further improvement is that, in step five, optimizing the parameters of the SRAF includes reducing the width of the SRAF.

[0038] The present invention can simulate different environments in which an SRAF is inserted by designing a series of first test pattern structures. At the same time, dense patterns are provided in the first and second dense pattern areas on both sides of the spacer area in the first test pattern structure. Since the dense patterns have the greatest impact on the light of the SRAF in the spacer area, after the SRAF is inserted into the spacer area of ​​the first test pattern structure, the security of various parameters of the SRAF can be well verified. For some unsafe SRAF parameters that cannot be detected by existing methods, the present invention can well detect them and optimize the SRAF parameters based on the detection results. The present invention is performed before the SRAF is inserted into the layout of the customer's product. Therefore, the present invention can accurately verify the security of the SRAF parameters in various environments in advance and optimize the parameters of unsafe SRAFs, thereby ensuring the security of the SRAF inserted into the layout corresponding to the product and reducing the risk of the SRAF being exposed and developed. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0040] Figure 1 This is a flow chart of the existing method for inserting SRAF in the layout;

[0041] Figure 2 It is a graphical structure used when screening SRAF parameters in the existing method of inserting SRAF into the layout;

[0042] Figure 3 is a flow chart of a risk prediction and optimization method of SRAF according to an embodiment of the present invention;

[0043] Figure 4 This is a flow chart of the risk prediction and optimization method of SRAF in a preferred embodiment of the present invention;

[0044] Figure 5 Schematic diagram of a first test pattern structure used in the SRAF risk prediction and optimization method according to an embodiment of the present invention;

[0045] Figure 6A The existing method of inserting SRAF in the layout is Figure 2 A simulation contour diagram obtained by simulating the graphic structure shown;

[0046] Figure 6B It is a simulation contour graph obtained by simulating the first test pattern structure before SRAF optimization in the SRAF risk prediction and optimization method according to an embodiment of the present invention;

[0047] Figure 6CIt is a simulation contour graph obtained by simulating the first test pattern structure after SRAF optimization in the SRAF risk prediction and optimization method according to an embodiment of the present invention;

[0048] Figure 7 3. This is a curve comparison diagram of the maximum light intensity value of SRAF before and after SRAF optimization in the SRAF risk prediction and optimization method of the preferred embodiment of the present invention;

[0049] Figure 8 This table shows the optimization of SRAFs of different spatial periods using the SRAF risk prediction and optimization method according to an embodiment of the present invention, as well as a comparison table of SRAF extraprinting before and after optimization. DETAILED DESCRIPTION

[0050] like Figure 3 As shown, it is a flow chart of the risk prediction and optimization method of SRAF204 according to an embodiment of the present invention; Figure 4 As shown, it is a flow chart of the risk prediction and optimization method of SRAF204 in a preferred embodiment of the present invention; Figure 5 FIG. 1 is a schematic diagram of a first test pattern structure used in the risk prediction and optimization method of SRAF 204 according to an embodiment of the present invention. The risk prediction and optimization method of SRAF 204 according to an embodiment of the present invention includes the following steps:

[0051] Step 1: Design a series of first test pattern structures. Each of the first test pattern structures includes a first dense pattern area 201a, a spacer area 202, and a second dense pattern area 201b. Dense patterns 203 are disposed in the first dense pattern area 201a and the second dense pattern area 201b. The width of the spacer area 202 in each of the first test pattern structures gradually changes. The width of the dense patterns 203 is W, and the spatial period of the arrangement of the dense patterns 203 is P.

[0052] A series of the first test pattern structures are used to simulate different environments in which the SRAF 204 is inserted, and the dense pattern 203 is used to enhance the optical impact on the SRAF 204 under different environments.

[0053] In the embodiment of the present invention, the line width and space period of the dense pattern 203 are set according to the line width and minimum space period allowed in the design rules of the corresponding key layer.

[0054] In the subsequent step 2, a rule-based technique is used to insert the SRAF 204. In some embodiments, the width of the spacer 202 of each first test pattern structure is determined based on the number of inserted SRAFs 204, and the width of the spacer 202 of each first test pattern structure is gradually changed by gradually changing the number of inserted SRAFs 204.

[0055] The spatial period of the dense pattern 203 is set to be greater than or equal to the minimum spatial period (Pmin) and less than or equal to the first width (Gap1) of the spacer 202. The first width is the width of the spacer 202 of the first test pattern structure when one SRAF 204 is inserted. This can be expressed as:

[0056] In some embodiments, in a series of the first test pattern structures, the number of the SRAFs 204 gradually changes from 1 to 6, and the corresponding widths of the spacers 202 are Gap1, Gap2, Gap3, Gap4, Gap5 and Gap6, respectively, with Gap1 to Gap6 increasing in sequence.

[0057] In a preferred embodiment of the present invention, step 1 corresponds to Figure 4 In step S201, a series of DL_gap_DL structure patterns are designed, where DL represents the dense pattern 203, gap represents the spacer 202, and DL_gap_DL represents the first test pattern structure.

[0058] Step 2: inserting SRAF 204 into the spacer area 202 of each first test pattern structure and performing OPC correction on each first test pattern structure after inserting the SRAF 204.

[0059] In the embodiment of the present invention, the SRAF 204 is inserted using a rule-based technique.

[0060] In some embodiments, the OPC correction is performed using an OPC optical model that establishes a process window.

[0061] In a preferred embodiment of the present invention, step 2 corresponds to Figure 4 In step S202, SRAF is inserted using Rule-based technology, and OPC correction is performed on the graphics.

[0062] Step 3: Utilize an OPC result checking program to simulate the simulation contour graph of each of the first test pattern structures.

[0063] In the embodiment of the present invention, the OPC result checking program simulates and generates a simulation profile of each of the first test pattern structures according to the process window and the light intensity threshold value Ith of the OPC model.

[0064] In some embodiments, the light intensity threshold adopts the previously verified minimum light intensity value required for the SRAF 204 to be exposed and developed.

[0065] In a preferred embodiment of the present invention, step three corresponds to Figure 4In step S203, the contour of the SRAF is simulated using the OPC result check program.

[0066] In a preferred embodiment of the present invention, after step 2 and before the subsequent step 4, the following steps are further included:

[0067] Step 6: Use the OPC optical model to simulate the maximum light intensity value of the SRAF 204 in each of the first test pattern structures.

[0068] When a plurality of SRAFs 204 are provided in the spacer 202 of the first test pattern structure, the maximum light intensity value is the maximum light intensity value of all the SRAFs 204 in the spacer 202 of the first test pattern structure.

[0069] Step 6 corresponds to Figure 4 In step S207, the maximum light intensity value Imax of the SRAF is calculated by simulation, where Imax represents the maximum light intensity value.

[0070] Step 4: Conduct risk assessment, including:

[0071] If the simulation contour graph does not include the contour graph of the SRAF 204 , the verification result is that the parameters of the SRAF 204 are safe.

[0072] If the simulation contour graph includes the contour graph of the SRAF 204, the verification result is that the parameters of the SRAF 204 are unsafe, and the process goes to step 5.

[0073] In a preferred embodiment of the present invention, step four includes Figure 4 In the risk judgment based on step S203, when it is judged that there is no contour, the process goes to step S204 and the SRAF parameters are safe; if the judgment result is that there is a contour, the process goes to step S205 and the SRAF parameters are unsafe.

[0074] In a preferred embodiment of the present invention, the risk assessment further includes:

[0075] Comparing the maximum light intensity value of the SRAF 204 in each of the first test pattern structures with a light intensity threshold, if the maximum light intensity value of the SRAF 204 is less than the light intensity threshold, a theoretical judgment result is that the parameters of the SRAF 204 are safe;

[0076] If the maximum light intensity value of the SRAF 204 is greater than or equal to the light intensity threshold, the theoretical judgment result is that the parameters of the SRAF 204 are unsafe, and the process goes to step 5;

[0077] In a preferred embodiment of the present invention, step four includes Figure 4 Based on the risk judgment performed in step S207, when it is judged that Imax is less than Ith, the process goes to step S204 and the SRAF parameters are safe; if the judgment result is Imax>Ith, the process goes to step S205 and the SRAF parameters are unsafe.

[0078] It can be seen that the theoretical judgment result based on step S207 and the verification result based on step S203 complement each other. The risk judgment based on step S203 is based directly on the simulation structure and is therefore the verification result. The risk judgment based on step S203 is based on numerical comparison and can also be theoretically derived, so the result is the theoretical judgment result.

[0079] Step 5: Optimize the parameters of the SRAF 204 that are not safe, then go to step 2, and repeat steps 2 to 4 or steps 2 to 5 until the parameters of the SRAF 204 are safe.

[0080] In the embodiment of the present invention, optimizing the parameters of the SRAF 204 includes reducing the width of the SRAF 204 .

[0081] In a preferred embodiment of the present invention, step five corresponds to Figure 4 In step S206, the SRAF parameters are optimized, and then the process goes to step S202.

[0082] By designing a series of first test pattern structures, the embodiment of the present invention can simulate different environments in which the SRAF 204 is inserted. Furthermore, dense patterns 203 are provided in both the first and second dense pattern areas 201b on either side of the spacer 202 in the first test pattern structure. Because the dense patterns 203 have the greatest impact on the light transmitted to the SRAF 204 in the spacer 202, the security of various parameters of the SRAF 204 can be effectively verified after the SRAF 204 is inserted into the spacer 202 of the first test pattern structure. The embodiment of the present invention can effectively detect unsafe SRAF 204 parameters that cannot be detected by existing methods and optimize the SRAF 204 parameters based on the detection results. The embodiment of the present invention is performed before the SRAF 204 is inserted into the layout of a customer's product. Therefore, the embodiment of the present invention can accurately verify the security of the SRAF 204 parameters in various environments and optimize the parameters of unsafe SRAF 204 in advance, thereby ensuring the security of the SRAF 204 when inserted into the corresponding product layout and reducing the risk of the SRAF 204 being exposed and developed.

[0083] By designing a pattern DL_gap_DL with a strong optical effect on SRAF, the embodiments of the present invention can accurately verify the security of various parameters of SRAF inserted based on Rule_based in different environments in advance and further optimize the SRAF rule, thereby ensuring the security of SRAF inserted in the customer's layout and reducing defects caused by SRAF exposure.

[0084] In order to more clearly describe the embodiment of the present invention, further explanation is given below with reference to parameters:

[0085] The design rules for the linear layout allow a line width of 45nm and a minimum space period (pitch) of 90nm. During the early SRAF screening of this key layer, the light intensity threshold Ith for SRAF exposure under this process condition was found to be 0.187203, and it was found that when space = 140nm, a SRAF with a line width of 20nm can be inserted in the middle of the space. When the safety of SRAF under this condition is verified according to the existing traditional screening SRAF rule layout, the layout is Figure 2 The grating structure shown has CD = 45nm / Pitch = 185nm, where CD is the critical dimension, corresponding to Figure 2 The line width W in the Pitch corresponds to Figure 2 After performing OPC correction, the OPC result check program is used to simulate the contour when the light intensity threshold Ith is 0.187203. The contour is as follows Figure 6A As shown, Figure 6A In the figure, the figure in the layout is represented by a mark 101a, the SRAF is represented by a mark 103a, and the simulated figure of the figure 101a in the contour formed by simulation is represented by a mark 101b; Figure 6A The simulation results show that no contour is displayed for the SRAF, indicating that it is safe to insert a 20nm SRAF into the center of the spacer with a space of 140nm in the layout. However, since the customer layout includes a variety of graphic structures with a space of 140nm, the optical impact of the graphics around the spacer with a space of 140nm on the inserted SRAF will be different and may be greater than Figure 2 The graphics shown have an optical impact on the SRAF, which can easily cause additional development, so each one needs to be debugged.

[0086] Different from the existing method, in the embodiment of the present invention, a series of Figure 5For the Dense Line_Gap_Dense Line (i.e., DL_Gap_DL) layout shown, the dense part has a CD of 45 nm, the Pitch value ranges from 90 nm to 140 nm, gap = 140 nm. Based on the Rule_based technology, a SRAF with a width of 20 nm is inserted at the center of the gap. Next, OPC correction is performed on this series of layouts, and then the OPC result checking program is used to simulate the contour when the light intensity threshold is 0.187203. The results are as Figure 6B shown. Figure 6B In it, the dense patterns in the layout are separately represented by the label 203a, and the SRAF is separately represented by the label 204a. The simulation pattern of the dense pattern 203a in the contour formed by the simulation is separately represented by the label 203b, and the simulation pattern of the SRAF 204a is separately represented by the label 204b. Therefore, it can be seen from the results that the SRAF has an obvious contour, i.e., contour204b, after lithography simulation; as Figure 7 shown, and the maximum light intensity value Imax corresponding to the SRAF, i.e., the label 301, is greater than Ith. Figure 7 The lower left corner of shows 4 dense patterns and one SRAF. The maximum light intensity value of the 4 dense patterns in the light intensity curve is the largest, and the maximum light intensity value of the SRAF is the smallest; from the simulation diagram and the light intensity test structure, it is shown that the SRAF in this environment has the risk of being exposed under this lithography process condition, and the SRAF needs to be further optimized. Next, the width of the SRAF is reduced to 18 nm, and the SRAF safety verification is carried out again according to the above process. As Figure 6C shown, when the SRAF line width is 18 nm, the OPC result checking program does not simulate the contour of the SRAF. Figure 6C In it, the SRAF is separately represented by the label 204c; similarly, as Figure 7 shown, and at this time Imax < Ith, that is, the maximum light intensity value corresponding to the optimized SRAF, i.e., the label 302, is less than Ith, indicating that the optimized SRAF rule is safe in this environment. For the safety of the SRAF corresponding to different Pitch conditions and the optimization results, see the Figure 8 table shown. Figure 8In the 90nm process, when inserting a 20nm SRAF with a Pitch of 92nm or 94nm, as with the 90nm process, the present invention also detects that additional printing will occur, indicating that SRAF extraprinting is YES. However, existing methods cannot detect security issues with these SRAFs. When inserting an SRAF with a Pitch greater than 94nm, SRAF extraprinting is NO, and no optimization is required. As with the 90nm process, optimizing the SRAF parameters for Pitches of 92nm and 94nm, adjusting the width to 19nm, eliminates additional printing, indicating that SRAF extraprinting is NO after optimization. Therefore, the present invention's method can accurately verify the security of SRAF addition rules in advance. This is particularly true for complex customer layouts. Preemptive verification of the security of exposure assist patterns allows for more efficient OPC mask publishing.

[0087] The present invention has been described in detail above by means of specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principles of the present invention, those skilled in the art may make many variations and improvements, which should also be considered as the scope of protection of the present invention.

Claims

1. A risk prediction and optimization method for SRAF, characterized in that: The steps include: Step 1: Design a series of first test pattern structures, each of which includes a first dense pattern area, a spacer area, and a second dense pattern area. Dense patterns are provided in the first dense pattern area and the second dense pattern area, and the width of the spacer area of ​​each first test pattern structure gradually changes. A series of the first test pattern structures are used to simulate different environments in which the SRAF is inserted, and the dense pattern is used to enhance the optical impact of the SRAF in different environments; Step 2: inserting an SRAF into the spacer area of ​​each of the first test pattern structures and performing OPC correction on each of the first test pattern structures after the SRAF is inserted; Step 3: simulating the simulation profile of each of the first test pattern structures using an OPC result checking program; Step 4: Conduct risk assessment, including: If the simulation contour graph does not include the contour graph of the SRAF, the verification result is that the parameters of the SRAF are safe; If the simulation contour graph includes the contour graph of the SRAF, the verification result is that the parameters of the SRAF are unsafe, and the process goes to step 5; Step 5: Optimize the parameters of the SRAFs that are unsafe, then go to step 2, and repeat steps 2 to 4 or steps 2 to 5 until the parameters of the SRAFs are safe.

2. The SRAF risk prediction and optimization method according to claim 1, wherein: After step 2 and before step 4, it also includes: Step 6: Use the OPC optical model to simulate the maximum light intensity value of the SRAF in each of the first test pattern structures.

3. The SRAF risk prediction and optimization method according to claim 2, wherein: In step 1, the line width and space period of the dense pattern are set according to the line width and minimum space period allowed in the design rules of the corresponding key layer.

4. The SRAF risk prediction and optimization method according to claim 3, wherein: In step 2, the SRAF is inserted using rule-based technology.

5. The SRAF risk prediction and optimization method according to claim 4, wherein: The width of the spacer of each first test pattern structure is determined according to the number of inserted SRAFs, and the width of the spacer of each first test pattern structure is gradually changed by gradually changing the number of inserted SRAFs.

6. The SRAF risk prediction and optimization method according to claim 5, wherein: In step 1, the spatial period of the dense pattern is set to be greater than or equal to the minimum spatial period and less than or equal to the first width of the spacer, where the first width is the width of the spacer of the first test pattern structure when one SRAF is inserted.

7. The SRAF risk prediction and optimization method according to claim 5, wherein: In step 1, in a series of the first test pattern structures, the number of the SRAFs gradually changes from 1 to 6.

8. The SRAF risk prediction and optimization method according to claim 5 or 7, wherein: When a plurality of SRAFs are provided in the spacer area of ​​the first test pattern structure, in step six, the maximum light intensity value is the maximum light intensity value of all the SRAFs in the spacer area of ​​the first test pattern structure.

9. The SRAF risk prediction and optimization method according to claim 1, wherein: In step 2, the OPC correction is performed using an OPC optical model with an established process window.

10. The SRAF risk prediction and optimization method according to claim 9, wherein: In step three, the OPC result checking program simulates a simulation profile of each of the first test pattern structures according to the process window and light intensity threshold of the OPC optical model.

11. The SRAF risk prediction and optimization method according to claim 2, wherein: The risk assessment in step 4 also includes: comparing the maximum light intensity value of the SRAF in each of the first test pattern structures with a light intensity threshold; if the maximum light intensity value of the SRAF is less than the light intensity threshold, a theoretical judgment result is that the parameters of the SRAF are safe; If the maximum light intensity value of the SRAF is greater than or equal to the light intensity threshold, the theoretical judgment result is that the parameters of the SRAF are unsafe, and the process goes to step 5; The theoretical judgment result and the verification result complement each other.

12. The SRAF risk prediction and optimization method according to claim 10 or 11, wherein: The light intensity threshold adopts the minimum light intensity value required for SRAF exposure and development verified in the early stage.

13. The SRAF risk prediction and optimization method according to claim 1, wherein: In step five, optimizing the parameters of the SRAF includes reducing the width of the SRAF.

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