Pattern placement error aware optimization
A method to improve a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus, the method including: computing a multi-variable cost function of a plurality of design variables that are characteristics of the lithographic process, and reconfiguring the characteristics of the lithographic process by adjusting the design variables until a predefined termination condition is satisfied. The multi-variable cost function may be a function of one or more pattern shift errors. Reconfiguration of the characteristics may be under one or more constraints on the one or more pattern shift errors.
1. A method to improve a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus, the method comprising:
computing, by a hardware computer system, a multi-variable cost function of a plurality of design variables that are characteristics of the lithographic process;
reconfiguring the characteristics of the lithographic process by adjusting the design variables until a predefined termination condition is satisfied, under a constraint on a value of pattern shift error, the value of pattern shift error being a value of a shift of a position essentially equidistant from opposite sides of a pattern from an intended location of the position; and
producing electronic data using the adjusted design variables to configure an aspect of the design layout, the lithographic process or the lithographic projection apparatus.
2. The method of claim 1 , wherein the pattern shift error is pattern-dependent.
3. The method of claim 1 , wherein the multi-variable cost function is an explicit function of the pattern shift error.
4. The method of claim 1 , wherein the pattern shift error comprises a pattern shift error measured at a location selected by a user of the lithographic apparatus.
5. The method of claim 1 , wherein the pattern shift error comprises a function of a difference between edge placement errors at two adjacent edges.
6. The method of claim 1 , wherein the pattern shift error comprises a shift between an intended projection of a pattern and an actual or simulated projection of the pattern.
7. The method of claim 1 , wherein the pattern shift error comprises a displacement between a center of an intended projection of a pattern and a center of an actual or simulated projection of the pattern.
8. The method of claim 7 , wherein the displacement is in one of two perpendicular axes.
9. The method of claim 1 , wherein computing the multi-variable cost function comprises simulating a resist image or an aerial image of the portion of the design layout.
10. The method of claim 1 , wherein the portion of the design layout comprises one or more selected from: an entire design layout, a clip, a section of a design layout that is known to have a critical feature, and/or a section of the design layout where a critical feature has been identified by a pattern selection method.
11. The method of claim 1 , wherein at least one of the design variables are under a constraint representing a physical restriction in a hardware implementation of the lithographic projection apparatus.
12. The method of claim 1 , wherein the cost function is a function of one or more selected from: edge placement error, critical dimension, resist contour distance, worst defect size, and/or best focus shift.
13. The method of claim 1 , wherein at least one of the plurality of design variables are characteristics of an illumination for within the lithographic projection apparatus and of the design layout.
14. The method of claim 1 , wherein the cost function is a function of a proximity effect.
15. A computer program product comprising a non-transitory computer readable medium having instructions recorded thereon, the instructions when executed by a computer system, configured to cause at least:
computation of a multi-variable cost function of a plurality of design variables that are characteristics of a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus; and
reconfiguration of the characteristics of the lithographic process by adjusting the design variables until a predefined termination condition is satisfied, under a constraint on a value of pattern shift error, the value of pattern shift error being a value of a shift of a position essentially equidistant from opposite sides of a pattern from an intended location of the position; and
production of electronic data using the adjusted design variables to configure an aspect of the design layout, the lithographic process or the lithographic projection apparatus.
16. The computer program product of claim 15 , wherein the pattern shift error is pattern-dependent.
17. The computer program product of claim 15 , wherein the multi-variable cost function is an explicit function of the pattern shift error.
18. The computer program product of claim 15 , wherein the pattern shift error comprises a pattern shift error measured at a location selected by a user of the lithographic apparatus.
19. The computer program product of claim 15 , wherein the pattern shift error comprises a function of a difference between edge placement errors at two adjacent edges.
20. The computer program product of claim 15 , wherein the pattern shift error comprises a shift between an intended projection of a pattern and an actual or simulated projection of the pattern.
21. The computer program product of claim 15 , wherein the pattern shift error comprises a displacement between a center of an intended projection of a pattern and a center of an actual or simulated projection of the pattern.
22. The computer program product of claim 15 , wherein computation of the multi-variable cost function comprises performance of a simulation of a resist image or an aerial image of the portion of the design layout.