Systems, masks, and methods for manufacturable masks

• US 20070009808A1
• Filed: 10/06/2005
• Published: 01/11/2007
• Est. Priority Date: 04/06/2003
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Luminescent Technologies, Inc. (KLA Corporation)
• Inventors: Abrams, Daniel, Irby, David
• Granted Patent: US 7,698,665 B2
• Time in Patent Office: Days
• US Class Current: 430/5
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G03F 1/68 Preparation processes not covered by groups G03F1/20 - G03F1/50

Abstract

Photomask patterns are represented using contours defined by mask functions or other formats. Given target pattern, contours may be optimized such that defined photomask, when used in photolithographic process, prints wafer pattern faithful to target pattern. Optimized patterns or blocks may be simplified for mask manufacturing.

Claims

1. A method of modifying a photomask pattern for producing a target pattern in a region of a photomask comprising:

providing a functional representation of a first photomask pattern comprising a first plurality of values over the area of the region of the photomask;

modifying the functional representation of the first photomask pattern to produce a functional representation of a second photomask pattern based, at least in part, upon a merit function for the target pattern;

wherein the functional representation of the second photomask pattern comprises a second plurality of values over the area of the region of the photomask;

wherein the functional representation of the first photomask pattern is capable of being fractured into a smaller number of rectangles than the functional representation of the second photomask pattern;

determining a functional representation of a third photomask pattern that is capable of being fractured into a smaller number of rectangles than the functional representation of the second photomask pattern;

wherein the functional representation of the third photomask pattern comprises a third plurality of values over the area of the region of the photomask;

wherein the value of the merit function for the third photomask pattern is improved relative to the first photomask pattern.

2. The method of claim 1, wherein the functional representation of each of the first photomask pattern, second photomask pattern and third photomask pattern is a pixel based representation.

3. The method of claim 1, wherein the functional representation of each of the first photomask pattern, second photomask pattern and third photomask pattern is a distance function.

4. The method of claim 1, further comprising converting the functional representation of the third photomask pattern into a polygon representation.

5. The method of claim 2, further comprising converting the functional representation of the third photomask pattern into a polygon representation.

6. The method of claim 5, wherein the polygon representation has a higher resolution than the pixel size used in the pixel based representation of the third photomask pattern.

7. The method of claim 1, wherein determining the functional representation of the third photomask pattern further comprises selecting adjacent values from the functional representation of the second photomask pattern that do not represent a straight boundary of the second photomask pattern and replacing them with values that represent a straight boundary for the third photomask pattern.

8. The method of claim 1, wherein determining the functional representation of the third photomask pattern further comprises selecting adjacent values from the functional representation of the second photomask pattern that do not represent a stair step boundary of the second photomask pattern and replacing them with values that represent a stair step boundary for the third photomask pattern.

9. The method of claim 1, wherein determining the functional representation of the third photomask pattern further comprises selecting adjacent values from the functional representation of the second photomask pattern that do not represent a 45 degree diagonal boundary of the second photomask pattern and replacing them with values that represent a 45 degree diagonal boundary for the third photomask pattern.

10. The method of claim 1, wherein the third photomask pattern has an area about equal to the second photomask pattern.

11. The method of claim 1, wherein the third photomask pattern has an area that is within ±

10% of the area of the second photomask pattern.

12. The method of claim 1, wherein determining the functional representation of the third photomask pattern further comprises comparing the area of the third photomask pattern to the area of the second photomask pattern.

13. The method of claim 1, wherein determining the functional representation of the third photomask pattern further comprises comparing a simulated wafer pattern for the third photomask pattern to a simulated wafer pattern for the second photomask pattern.

14. The method of claim 1, wherein the value of the merit function for the second photomask pattern is better than the merit function for the third photomask pattern;

and wherein the value of the merit function for the third photomask pattern is closer to the value of the merit function for the second photomask pattern than to the value of the merit function for the first photomask pattern.

15. The method of claim 1, wherein the value of the merit function for the third photomask pattern is within one percent of the value of the merit function for the third photomask pattern.

16. A method of modifying a photomask pattern:

identifying a plurality of short segments along a contour of a first photomask pattern;

replacing the plurality of short segments with at least one segment that is longer than each of the short segments to produce a second photomask pattern; and

determining whether the second photomask pattern meets a merit threshold.

17. The method of claim 16, wherein the merit threshold comprises a comparison of the area of the first photomask pattern to the area of the second photomask pattern.

18. The method of claim 16, wherein the merit threshold comprises a comparison of a simulated wafer pattern for the first photomask pattern relative to a simulated wafer pattern for the second photomask pattern.

19. The method of claim 16, wherein the second photomask pattern is capable of being fractured into a smaller number of rectangles than the first photomask pattern.

20. The method of claim 16, replacing the plurality of short segments further comprises replacing the plurality of short segments with a stair step pattern that includes the at least one segment that is longer than each of the short segments.

21. The method of claim 16, replacing the plurality of short segments further comprises replacing the plurality of short segments with a pattern that includes at least one manhattan segment and at least one diagonal segment.

22. A method of modifying a photomask pattern for producing a target pattern:

providing a pixel based representation of a first photomask pattern;

identifying a plurality of adjacent pixels in the representation of the first photomask pattern that do not represent a straight edge of the photomask pattern;

producing a representation of a second photomask pattern that includes a representation of a straight edge in place of the plurality of adjacent pixels; and

optimizing the second photomask pattern for producing the target pattern by moving the straight edge.

23. The method of claim 22, wherein optimizing the second photomask pattern for producing the target pattern by moving the straight edge further comprises using model based optical proximity correction.

24. A method of modifying a photomask pattern for producing a target pattern:

providing a first photomask pattern;

producing a second photomask pattern from the first photomask pattern by iteratively adjusting the position of a plurality of edge segments of the first photomask pattern, wherein the plurality of edge segments correspond to portions of the photomask having a length less than 30 nanometers;

producing a third photomask pattern from the second photomask pattern that is capable of being fractured into a smaller number of rectangles than the second photomask pattern and that is optimized for producing the target pattern relative to the first photomask pattern.

25. The method of claim 24, wherein the plurality of edge segments includes more than a million edge segments having a length less than 30 nanometers.

26. The method of claim 24, wherein the plurality of edge segments correspond to portions of the photomask having a length less than 10 nanometers.

28. The method of claim 24, wherein iteratively modifying the portion of the pattern for each block to produce a first optimized pattern for the block further comprises using optical proximity correction for a plurality of edge segments.

29. The method of claim 28, wherein each edge segment corresponds to a portion of a photomask having a length of less than 30 nanometers.

30. The method of claim 28, wherein each edge segment corresponds to a portion of a photomask having a length of less than 10 nanometers.

35. The method of claim 29, wherein there are more than a million blocks.

27. A method of modifying a photomask pattern for producing a target pattern:

providing a first photomask pattern;

dividing the first photomask pattern into a plurality of blocks containing portions of the pattern;

iteratively modifying the portion of the pattern for each block to produce a first optimized pattern for the block; and

generating a second optimized pattern for each block that is capable of being fractured into a smaller number of rectangles than the first optimized pattern for the block.

31. The method of claim 27, wherein iteratively modifying the portion of the pattern for each block to produce a first optimized pattern for the block further comprises modifying a distance function that represents the portion of the pattern in each block.

32. The method of claim 27, wherein the blocks include halo regions.

33. The method of claim 27, further comprising assembling the second optimized pattern for each block to produce an optimized pattern corresponding to the area represented by the first photomask pattern.

34. The method of claim 33, wherein there are more than a million blocks.