Systems, masks, and methods for manufacturable masks using a functional representation of polygon pattern
View Patent ↗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.
1. A computer-implemented 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 second photomask pattern and 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; and
wherein the functional representation of the second photomask pattern includes polygons having a smaller number of vertices than corresponding polygons in the functional representation of the first photomask pattern; and
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; and
wherein a merit function over the area of the region of the photomask for the third photomask pattern and the target pattern is improved relative to a merit function over the area of the region of the photomask for the first photomask pattern and the target pattern.
2. The computer-implemented 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 computer-implemented method of claim 2 , further comprising convening the functional representation of the third photomask pattern into a polygon representation.
4. The computer-implemented method of claim 3 , wherein the polygon representation has a higher resolution than the pixel size used in the pixel based representation of the third photomask pattern.
5. The computer-implemented 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.
6. The computer-implemented method of claim 1 , further comprising converting the functional representation of the third photomask pattern into a polygon representation.
7. The computer-implemented 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 computer-implemented 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 computer-implemented 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 computer-implemented method of claim 1 , wherein the third photomask pattern has an area about equal to the second photomask pattern.
11. The computer-implemented 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 computer-implemented 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 computer-implemented 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 computer-implemented method of claim 1 , wherein a merit function over the area of the region of the photomask for the second photomask pattern and the target pattern is improved relative to a merit function over the area of the region of the photomask for the third photomask pattern and the target pattern;
and wherein the merit function for the third photomask pattern is closer to the merit function for the second photomask pattern than to the merit function for the first photomask pattern.
15. The computer-implemented method of claim 1 , wherein a merit function over the area of the region of the photomask for the third photomask pattern and the target pattern is within one percent of a merit function over the area of the region of the photomask for the second photomask pattern and the target pattern.