Feature optimization using enhanced interference mapping lithography
Disclosed concepts include a method of, and program product for, optimizing an intensity profile of a pattern to be formed in a surface of a substrate relative to a given mask using an optical system. Steps include mathematically representing resolvable feature(s) from the given mask, generating a mathematical expression, an eigenfunction, representing certain characteristics of the optical system, modifying the mathematical the eigenfunction by filtering, generating an interference map in accordance with the filtered eigenfunction and the mathematical expression of the given mask, and determining assist features for the given mask based on the interference map. As a result, undesired printing in the surface of the substrate may be minimized.
1. A method of optimizing an intensity profile of a pattern to be formed in a surface of a substrate relative to a given mask utilizing an optical system, comprising the steps of:
(a) mathematically representing a goal function representing desired printing behavior of the given mask;
(b) generating a mathematical expression representing certain characteristics of the optical system;
(c) modifying the mathematical expression of Step (b);
(d) generating an interference map in accordance with the result of Step (c) and Step (a); and
(e) determining assist features for the given mask based on the interference map of Step (d),
wherein modifying the mathematical expression of Step (b) minimizes undesired printing in the surface of the substrate.
2. The method of optimizing an intensity profile according to claim 1 , wherein the mathematical expression generated in Step (b) is at least one eigenfunction representing certain characteristics of the optical system.
3. The method of optimizing an intensity profile according to claim 2 , wherein modifying the mathematical expression of Step (b) includes filtering the at least one eigenfunction.
4. The method of optimizing an intensity profile according to claim 3 , wherein the at least one eigenfunction is filtered relative to the sidelobes of the eigenfunction.
5. The method of optimizing an intensity profile according to claim 3 , wherein the at least one eigenfunction is filtered outside of the main lobe of the eigenfunction.
6. The method of optimizing an intensity profile according to claim 3 , wherein the filtering removes the DC component or certain low spatial frequencies of the eigenfunction.
7. The method of optimizing an intensity profile according to claim 3 , wherein the filtering enhances the eigenfunction for minimizing local imbalances of in-phase assist features and out-of-phase assist features generated in Step (e).
8. The method of optimizing an intensity profile according to claim 3 , wherein the interference map in Step (d) is generated by convolving the result of Step (a) with the result of Step (c).
9. The method of optimizing an intensity profile according to claim 1 , wherein step (e) includes selecting in-phase assist features and out-of-phase assist features corresponding to the interference map.
10. A program product, comprising executable code transportable by at least one machine readable medium, wherein execution of the code by at least one programmable computer causes the at least one programmable computer to perform a sequence of steps for optimizing an intensity profile of a pattern to be formed in a surface of a substrate for a given mask utilizing an optical system, compromising:
(a) mathematically representing a goal function representing desired printing behavior of the given mask;
(b) generating a mathematical expression representing certain characteristics of the optical system;
(c) modifying the mathematical expression of Step (b);
(d) generating an interference map in accordance with the result of Step (c) and Step (a); and
(e) determining assist features for the given mask based on the interference map of Step (d),
wherein modifying the mathematical expression of Step (b) minimizes undesired printing in the surface of the substrate.
11. The method of optimizing an intensity profile according to claim 10 , wherein the mathematical expression generated in Step (b) is at least one eigenfunction representing certain characteristics of the optical system.
12. The method of optimizing an intensity profile according to claim 11 , wherein modifying the mathematical expression of Step (b) includes filtering the at least one eigenfunction.
13. The method of optimizing an intensity profile according to claim 12 , wherein the at least one eigenfunction is filtered relative to the sidelobes of the eigenfunction.
14. The method of optimizing an intensity profile according to claim 12 , wherein the at least one eigenfunction is filtered outside of the main lobe of the eigenfunction.
15. The method of optimizing an intensity profile according to claim 12 , wherein the filtering removes the DC component or certain low spatial frequencies of the eigenfunction.
16. The method of optimizing an intensity profile according to claim 12 , wherein the filtering enhances the eigenfunction for minimizing local imbalances of in-phase assist features and out-of-phase assist features generated in Step (e).
17. The method of optimizing an intensity profile according to claim 12 , wherein the interference map in Step (d) is generated by convolving the result of Step (a) with the result of Step (c).
18. The method of optimizing an intensity profile according to claim 10 , wherein step (e) includes selecting in-phase assist features an out-of-phase assist features corresponding to the interference map.
19. A method of designing an optimal mask, comprising the steps of:
(a) generating an intensity profile of a pattern to be formed in a surface of a substrate relative to a given mask utilizing an optical system;
(b) mathematically representing a goal function representing desired printing behavior of the given mask;
(c) generating a mathematical expression representing certain characteristics of the optical system;
(d) modifying the mathematical expression of Step (c);
(e) generating an interference map in accordance with the result of Step (d) and Step (b); and
(f) determining assist features for the given mask based on the interference map of Step (e), wherein modifying the mathematical expression of Step (c) minimizes undesired printing in the surface of the substrate.
20. The method of optimizing an intensity profile according to claim 19 , wherein the mathematical expression generated in Step (c) is at least one eigenfunction representing certain characteristics of the optical system.
21. The method of optimizing an intensity profile according to claim 20 , wherein modifying the mathematical expression of Step (c) includes filtering the at least one eigenfunction.
22. The method of optimizing an intensity profile according to claim 21 , wherein the at least one eigenfunction is filtered relative to the sidelobes of the eigenfunction.
23. The method of optimizing an intensity profile according to claim 21 , wherein the at least one eigenfunction is filtered outside of the main lobe of the eigenfunction.
24. The method of optimizing an intensity profile according to claim 21 , wherein the filtering removes the DC component or certain low spatial frequencies of the eigenfunction.
25. The method of optimizing an intensity profile according to claim 21 , wherein the filtering enhances the eigenfunction for minimizing local imbalances of in-phase assist features and out-of-phase assist features generated in Step (f).
26. The method of optimizing an intensity profile according to claim 21 , wherein the interference map in Step (e) is generated by convolving the result of Step (b) with the result of Step (d).
27. The method of optimizing an intensity profile according to claim 20 , wherein step (f) includes selecting in-phase assist features and out-of-phase assist features corresponding to the interference map.