A method for optimizing the main image of CT slices for OPC correction

Abstract

This invention discloses a method for optimizing the main pattern of a CT layer applied to OPC correction. The invention introduces a risk function and an activity domain to constrain the movement range of the main pattern of the CT layer. By moving the position of the main pattern, more sub-resolution assist features (SRAFs) can be added during CT layer OPC correction, increasing the overall process window (PW) of the main pattern of the CT layer and improving the yield of manufactured semiconductor devices.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit lithography technology and relates to a method for optimizing the main pattern of the CT layer applied to OPC correction. Background Technology

[0002] In photolithography, the process window (PW) is crucial, directly impacting the yield of semiconductor device manufacturing. The contact layer (CT layer), a vital layer in photolithography, benefits from a larger PW, leading to higher yields in subsequent semiconductor manufacturing. Sub-resolution assist features (SRAFs) are added between independent or semi-independent master patterns to enlarge the PW. Currently, a rule-based SRAF addition method is primarily used, where several SRAFs are added when the spacing between master patterns is greater than or equal to a certain value.

[0003] In the current OPC correction of the CT layer, the main pattern is fixed. When the distance between two main patterns is slightly less than the minimum distance for adding SRAF, the sub-resolution auxiliary pattern (SRAF) cannot be inserted. This results in insufficient process windows for some patterns, thereby reducing the semiconductor manufacturing yield.

[0004] Therefore, a method for optimizing the main image of CT slices is needed to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for optimizing the main pattern of the CT layer in OPC correction, which can improve the process window and increase the yield of semiconductor manufacturing.

[0006] In a first aspect, the present invention provides a method for optimizing the main pattern of a CT layer applied to OPC correction, specifically:

[0007] S1: Obtain the target layout of the CT layer; the target layout includes several main graphics;

[0008] S2: Determine whether the distance L0 between any two adjacent main graphics is greater than or equal to 2b+c. If it is, the sub-resolution auxiliary graphic SRAF placement rule is satisfied. Otherwise, determine whether 2b+c-θ≤L0<2b+c is satisfied. If satisfied, these two main graphics are used as the main graphics to be optimized. If not satisfied, the sub-resolution auxiliary graphic SRAF cannot be placed. Where b represents the distance from SRAF to the main graphic in nm, c represents the width of SRAF in nm, d represents the distance from SRAF to SRAF in nm, and θ represents the preset parameter, which is 4nm in this invention.

[0009] S3: The process of correcting the main graphic to be optimized:

[0010] 3-1 Construct a risk function to measure the magnitude of risk present at the current position after the main graphic moves. That is, when the main graphic moves to a certain position, it is affected by risk factors and generates a specific risk value. The risk function is the weighted sum of all risk factors, as shown in the following formula:

[0011]

[0012] Where Φ sum For risk function, These are the risk factors for the main pattern movement of the CT layer, the associated risk factors for the metal layer, the associated risk factors for the polysilicon layer, and the associated risk factors for the refractory metal silicide layer; n1, n2, n3, and n4 are the number of the corresponding risk factors. These are the weights for the corresponding risk factors. Since each risk factor originates from a different layer, the weights need to be adjusted according to the actual situation of the production line.

[0013] Preferably, the risk factors for movement of the main image in the CT layer include the spacing between the main image and adjacent main images;

[0014] Preferably, the associated risk factors of the metal layer include the coverage area of ​​the main graphic and the corresponding graphic of the metal layer, and the spacing between the main graphic and the adjacent metal layer graphic.

[0015] Preferably, the associated risk factors of the polysilicon poly layer include the spacing between the main pattern and the poly layer pattern;

[0016] Preferably, the associated risk factors of the refractory metal silicide layer include the contact area between the main pattern and the corresponding pattern of the silicide layer, and the spacing between adjacent patterns of the main pattern and the silicide layer.

[0017] 3-2 Determine the risk threshold based on semiconductor manufacturing process requirements;

[0018] 3-3 Assuming that the initial positions of the adjacent main images to be optimized in the CT layer are set symmetrically, the two main images to be optimized each move around the perimeter, and the risk function value of the main image after each direction of movement is equal to the risk threshold, then the current position is considered to be the risk critical position; finally, the active domain of the current main image is enclosed by all the risk critical positions in the four directions of the main image.

[0019] 3-4 Move along the center line connecting the two main graphics to be optimized. Within the active domain of each main graphic, determine whether the distance L1 after the movement can reach 2b+c. If so, fix the main graphic to be optimized at the current position and insert SRAF to complete the optimization of the main graphic. Otherwise, first place the two main graphics at the maximum distance along the direction connecting the centers of the two main graphics, and then move along the direction perpendicular to the direction connecting the centers of the two main graphics until the boundary of the active domain of the two main graphics is reached. Fix the main graphic to be optimized at the current position and insert SRAF to complete the optimization of the main graphic.

[0020] Secondly, the present invention provides a mask, which is obtained by using the method to perform sub-resolution auxiliary graphic layout and then modifying it.

[0021] Thirdly, the present invention provides a device for correcting a photomask pattern, comprising:

[0022] The data acquisition module acquires the target layout of the CT layer;

[0023] The main pattern correction module performs OPC correction on the target pattern of the above CT layer after correction using the method, in all directions where the manufacturability rules of each mask are not restricted.

[0024] Fourthly, the present invention provides a computer device including a memory, a modifier, and a computer program stored in the memory and executable on the modifier, wherein the modifier implements the steps of the method when executing the computer program.

[0025] Fifthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a modifier, implements the steps of the method.

[0026] The beneficial effects of this invention are:

[0027] This invention introduces a risk function and an active domain to constrain the movement range of the CT layer master pattern. By moving the position of the CT layer master pattern, SRAF can be added more fully in the CT layer OPC correction, increasing the overall process window (PW) of the CT layer master pattern and improving the yield of semiconductor device production. Attached Figure Description

[0028] Figure 1 This is a flowchart of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of a CT layer;

[0030] Figure 3 This is a schematic diagram illustrating the relationships between the different layers of the map.

[0031] Figure 4 To correct the first process demonstration, (a) the distance L0 between the main graphics A and B is 2b+c-θ≤L0<2b+c, and (b) the main graphics A and B move along the line connecting the centers of the main graphics. Within the respective activity domains of the two main graphics, it is determined that the distance L1 after the movement can reach 2b+c.

[0032] Figure 5 To correct the second process demonstration, (a) the distance L0 between the main graphics A and B is 2b+c-θ≤L0<2b+c; (b) the main graphics A and B move along the center line connecting the main graphics, and it is determined within the respective activity domains of the two main graphics that the distance L1 after the movement cannot reach 2b+c; (b) the main graphics A and B move along the center line perpendicular to the main graphics. Detailed Implementation

[0033] The present invention will now be further analyzed with reference to the accompanying drawings.

[0034] The purpose of optimizing the CT layer master pattern is to increase the process window and improve semiconductor manufacturing yield. By selecting and moving some adjacent master patterns, the spacing between these adjacent master patterns, which were originally too small to allow the addition of SRAFs, is increased to the point where SRAFs can be inserted, thereby completing the optimization and increasing the process window.

[0035] The selection of adjacent primary graphics to be optimized depends on the determination of the SRAF placement rules. Subthreshold auxiliary graphics (SRAF), as a commonly used resolution enhancement technique, are added between independent or semi-independent graphics to improve the process window. The SRAF placement rules mainly include three parameters: the distance b from the SRAF to the primary graphic, the width c of the SRAF, and the distance d between SRAFs, such as... Figure 2 As shown.

[0036] A method for optimizing the main image of a CT slice is as follows:

[0037] S1: Obtain the target layout of the CT layer; the target layout includes several main graphics;

[0038] S2: Determine whether the distance L0 between any two adjacent main graphics is greater than or equal to 2b+c. If it is, the sub-resolution auxiliary graphic SRAF placement rule is satisfied. Otherwise, determine whether 2b+c-θ≤L0<2b+c is satisfied. If satisfied, these two main graphics are used as the main graphics to be optimized. If not satisfied, the sub-resolution auxiliary graphic SRAF cannot be placed. Where b represents the distance from SRAF to the main graphic in nm, c represents the width of SRAF in nm, d represents the distance from SRAF to SRAF in nm, and θ represents the preset parameter, which is 4nm in this invention.

[0039] S3: The process of correcting the main graphic to be optimized:

[0040] 3-1 Construct a risk function to measure the magnitude of risk present at the current position after the main graphic moves. That is, when the main graphic moves to a certain position, it is affected by risk factors and generates a specific risk value. The risk function is the weighted sum of all risk factors, as shown in the following formula:

[0041]

[0042] Where Φ sum For risk function, These are the risk factors for the main pattern movement of the CT layer, the associated risk factors for the metal layer, the associated risk factors for the polysilicon layer, and the associated risk factors for the refractory metal silicide layer; n1, n2, n3, and n4 are the number of the corresponding risk factors. These are the weights for the corresponding risk factors. Since each risk factor originates from a different layer, the weights need to be adjusted according to the actual situation of the production line.

[0043] like Figure 3 According to the semiconductor manufacturing process, the CT layer connects the metal layer and the IMP layer, and these two layers are connected by a refractory metal silicide layer. Therefore, it is necessary to consider the connection relationship between the CT layer and the silicide layer at their contact points. In addition, attention should be paid to the positional relationship between the CT layer and the poly layer.

[0044] In summary, the main sources of cross-layer risk affecting the movement of the main CT image include the following:

[0045] Metal layer:

[0046] a. The contact area between the graphic and the metal layer is too small, which can easily lead to breakage.

[0047] b. The spacing between adjacent patterns of the metal layer should not be too small, as this can lead to risks such as short circuits.

[0048] Poly layer:

[0049] c. The spacing between the graphic and the poly layer should not be too small, as this can lead to risks such as short circuits.

[0050] silicide layer:

[0051] d. The contact area between the graphic and the silicide layer is too small, as it is prone to breakage.

[0052] e. The spacing between adjacent graphics to the silicide layer should not be too small, as this can lead to risks such as short circuits.

[0053] 3-2 Determine the risk threshold based on semiconductor manufacturing process requirements;

[0054] 3-3 Assuming the initial positions of adjacent master images to be optimized in the CT layer are axially symmetric, and the two master images to be optimized each move in all four directions, ensuring that the risk function value of the master image after each direction of movement equals the risk threshold, then the current position in that direction is considered a critical risk position; finally, the activity domain of the current master image is formed by all the critical risk positions in the four directions around it. See Figure 4-5 Dashed box;

[0055] 3-4 Move along the center line connecting the two main graphics to be optimized. Within the active domain of each main graphic, determine whether the distance L1 after the movement can reach 2b+c. If so, fix the main graphic to be optimized at the current position and insert SRAF to complete the optimization of the main graphic. Otherwise, move along the direction of the center line connecting the two main graphics, first move the two main graphics away from each other, and then move along the direction perpendicular to the center line connecting the two main graphics until the boundary of the active domain of the two main graphics is reached. Fix the main graphic to be optimized at the current position and insert SRAF to complete the optimization of the main graphic.

[0056] like Figure 4 (a) According to the rules, select the adjacent main graphics to be optimized, namely graphics A and graphics B. The distance between the two main graphics is slightly less than (2b+c), so SRAF patterns cannot be inserted. Figure 4 (b) Determine the activity domains of the two main graphs based on the risk function and risk threshold; for example... Figure 4 (c) Move graphic B along the line connecting the centers of the two main graphics according to the active area of ​​the dashed box until the distance between the two graphics reaches (2b+c), then stop moving; Figure 4 (d) Add SRAF globally to complete the main graphic optimization.

[0057] like Figure 5 (a) According to the rules, select the adjacent main graphics to be optimized, namely graphics A and graphics B. The distance between the two main graphics is slightly less than (2b+c), so SRAF patterns cannot be inserted. Figure 5 (b) The activity domain is calculated based on the risk function; for example... Figure 5 (c) It was found that graphic A could hardly be moved, and even after moving B along the line connecting the centers of the two main graphics to the edge of the active domain, the distance between A and B was still less than (2b+c), making it impossible to insert SRAF. Therefore, based on the active domain selection, graphics A and B were moved along the line perpendicular to the line connecting the centers of the two main graphics to the position furthest from the active domain; for example... Figure 5 (d) Add SRAF globally to complete the main graphic optimization.

Claims

1. A method for optimizing the main pattern of a CT layer applied to OPC correction, characterized in that... The method is specifically as follows: S1: Obtain the target layout of the CT layer; the target layout includes several main graphics; S2: Determine whether the distance L0 between any two adjacent main graphics is greater than or equal to 2b+c. If it is, the sub-resolution auxiliary graphic SRAF placement rule is satisfied. Otherwise, determine whether 2b+c-θ≤L0<2b+c is satisfied. If satisfied, these two main graphics are used as the main graphics to be optimized. If not satisfied, SRAF cannot be placed. Where b represents the distance from SRAF to the main graphic in nm, c represents the width of SRAF in nm, d represents the distance from SRAF to SRAF in nm, and θ represents the preset parameter. S3: The process of correcting the main graphic to be optimized: 3-1 Construct a risk function to measure the magnitude of risk present at the current position after the main graphic moves. That is, when the main graphic moves to a certain position, it is affected by risk factors and generates a specific risk value. The risk function is the weighted sum of all risk factors, as shown in the following formula: Where Φ sum For risk function, These are the risk factors for the main image movement in the CT layer, the associated risk factors in the metal layer, the associated risk factors in the poly layer, and the associated risk factors in the silicide layer, respectively; n1, n2, n3, and n4 are the number of each corresponding risk factor. These are the weights of the corresponding risk factors; 3-2 Determine the risk threshold based on semiconductor manufacturing process requirements; 3-3 Assuming that the initial positions of the adjacent main images to be optimized in the CT layer are set symmetrically, the two main images to be optimized each move around the perimeter, and the risk function value of the main image after each direction of movement is equal to the risk threshold, then the current position is considered to be the risk critical position; finally, the active domain of the current main image is enclosed by all the risk critical positions in the four directions of the main image. 3-4 Move along the center line connecting the two main graphics to be optimized. Within the active domain of each main graphic, determine whether the distance L1 after the movement can reach 2b+c. If so, fix the main graphic to be optimized at the current position and insert SRAF to complete the optimization of the main graphic. Otherwise, first place the two main graphics at the maximum distance along the direction connecting the centers of the two main graphics, and then move along the direction perpendicular to the direction connecting the centers of the two main graphics until the boundary of the active domain of the two main graphics is reached. Fix the main graphic to be optimized at the current position and insert SRAF to complete the optimization of the main graphic.

2. The method according to claim 1, characterized in that... The risk factors for movement of the main image in the CT slice include the spacing between the main image and adjacent main images.

3. The method according to claim 1, characterized in that... The associated risk factors of the metal layer include the coverage area of ​​the main graphic and the corresponding graphic of the metal layer, and the spacing between the main graphic and the adjacent metal layer graphic.

4. The method according to claim 1, characterized in that... The associated risk factors of the poly layer include the spacing between the main graphic and the poly layer graphic.

5. The method according to claim 1, characterized in that... The associated risk factors of the silicide layer include the contact area between the main graphic and the corresponding graphic of the silicide layer, and the spacing between the main graphic and adjacent graphics of the silicide layer.

6. A photomask, characterized in that... The main graphic layout is corrected using the method described in any one of claims 1-5, and then a sub-resolution auxiliary graphic is inserted.

7. A device for correcting a mask pattern, characterized in that, include: The data acquisition module acquires the target layout of the CT layer; The main pattern correction module performs OPC correction on the target pattern of the above CT layer using the method described in any one of claims 1-5 in all directions where the manufacturability rules of each mask are not restricted.

8. A computer device comprising a memory, a modifier, and a computer program stored in the memory and executable on the modifier, characterized in that, When the corrector executes the computer program, it implements the steps of the method as described in any one of claims 1-5.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the corrector, it implements the steps of the method as described in any one of claims 1-5.

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