Method for Time-Evolving Rectilinear Contours Representing Photo Masks

• US 20070136716A1
• Filed: 02/12/2007
• Published: 06/14/2007
• Est. Priority Date: 04/06/2003
• Status: Active Grant

• Current Assignee: KLA Corporation
• Original Assignee: Luminescent Technologies, Inc. (KLA Corporation)
• Inventors: Osher, Stanley, Abrams, Daniel, Peng, Danping
• Granted Patent: US 7,703,068 B2
• Time in Patent Office: Days
• US Class Current: 716/54
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes

Abstract

Photomask patterns are represented using contours defined by level-set functions. Given target pattern, contours are optimized such that defined photomask, when used in photolithographic process, prints wafer pattern faithful to target pattern. Optimization utilizes “merit function” for encoding aspects of photolithographic process, preferences relating to resulting pattern (e.g. restriction to rectilinear patterns), robustness against process variations, as well as restrictions imposed relating to practical and economic manufacturability of photomasks.

Claims

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17. A method for determining a mask pattern to be used on a photo-mask in a photolithographic process, wherein the photo-mask has a plurality of distinct types of regions having distinct optical properties, comprising:

providing a first mask pattern that includes a plurality of distinct types of regions corresponding to the distinct types of regions of the photo-mask;

determining a first function corresponding to the first mask pattern, wherein the range of the first function has a cardinality that is greater than the number of distinct types of regions of the first mask pattern, and wherein the domain of the first function corresponds to the plane of the first mask pattern; and

generating a second function based, at least in part, on the first function, wherein the second function corresponds to a second mask pattern.

18. The method of claim 17, further comprising extracting the second mask pattern from the second function.

19. The method of claim 18, wherein the extracting includes calculating a first group that includes one or more regions corresponding to a first value of the second function.

20. The method of claim 19, wherein the extracting includes calculating a second group that includes one or more regions corresponding to a second value of the second function.

21. The method of claim 20, wherein the extracting includes performing a logical operation on the first group and the second group.

22. The method of claim 17, wherein the generating is in accordance with a model of the photolithographic process.

23. The method of claim 17, wherein the generating includes modifying the first function in accordance with a model of the photolithographic process.

24. The method of claim 17, wherein the number of distinct types of regions of the fist mask pattern is 2.

25. The method of claim 24, wherein the distinct types of regions of the first mask pattern include a chrome region and a glass region.

26. The method of claim 24, wherein the distinct types of regions of the first mask pattern include a region having a transmissivity greater than a pre-determined value and an attenuating phase-shifting region.

27. The method of claim 17, wherein first mask pattern corresponds to a chrome-on-glass photo-mask, a phase-shift photo-mask, an attenuated phase-shift photo-mask, or a multiple exposure photo-mask.

28. The method of claim 17, wherein the first function includes a level-set function.

29. The method of claim 17, wherein the first function is a grayscale or a bitmap representation of the first mask pattern.

30. The method of claim 17, wherein first function includes at least three values, and wherein a first value and a second value correspond to regions of the first mask pattern, and a third value corresponds to a contour in a plane of the first mask pattern.

31. The method of claim 30, wherein the regions corresponding to the first value and the second value are distinct from each other.

32. The method of claim 17, wherein the generating is in accordance with at least a portion of a target pattern that is to be printed by the photo-mask during the photolithographic process, and wherein at least the portion of the target pattern corresponds to a physical layout of at least a portion of an integrated circuit.

33. The method of claim 32, wherein at least the portion of the target pattern includes a format that is compatible with GDSII or OASIS.

34. The method of claim 17, wherein the first function is a distance function in which a value of the first function corresponds to a distance from a nearest contour in the plane of the first mask pattern.

35. The method of claim 17, wherein the first function has a pre-determined value on a contour in the plane.

36. The method of claim 17, further comprising adjusting the second function such that it is a distance function in which a value of the second function corresponds to a distance from a nearest contour in a plane of the second mask pattern.

37. The method of claim 17, wherein values of the first function indicate a position of a contour separating distinct regions on the photo-mask.

38. A computer-program product for use in conjunction with a computer system, the computer-program product comprising a computer-readable storage medium and a computer-program mechanism embedded therein for determining a mask pattern to be used on a photo-mask in a photolithographic process, wherein the photo-mask has a plurality of distinct types of regions having distinct optical properties, the computer-program mechanism including:

instructions for providing a first mask pattern that includes a plurality of distinct types of regions corresponding to the distinct types of regions of the photo-mask;

instructions for determining a first function corresponding to the first mask pattern, wherein the range of the first function has a cardinality that is greater than the number of distinct types of regions of the first mask pattern, and wherein the domain of the first function corresponds to the plane of the first mask pattern; and

instructions for generating a second function based, at least in part, on the first function, wherein the second function corresponds to a second mask pattern.

39. A computer system, comprising:

at least one processor;

at least one memory; and

at least one program module, the program module stored in the memory and configured to be executed by the processor, wherein at least the program module is for determining a mask pattern to be used on a photo-mask in a photolithographic process, and wherein the photo-mask has a plurality of distinct types of regions having distinct optical properties, at least the program module including;

instructions for providing a first mask pattern that includes a plurality of distinct types of regions corresponding to the distinct types of regions of the photo-mask;

instructions for determining a first function corresponding to the first mask pattern, wherein the range of the first function has a cardinality that is greater than the number of distinct types of regions of the first mask pattern, and wherein the domain of the first function corresponds to the plane of the first mask pattern; and

instructions for generating a second function based, at least in part, on the first function, wherein the second function corresponds to a second mask pattern.

40. A computer system, comprising:

means for computing;

means for storing; and

at least one program module mechanism, the program module mechanism stored in at least the means for storing and configured to be executed by at least the means for computing, wherein at least the program module mechanism is for determining a mask pattern to be used on a photo-mask in a photolithographic process, and wherein the photo-mask has a plurality of distinct types of regions having distinct optical properties, at least the program module mechanism including;

instructions for providing a first mask pattern that includes a plurality of distinct types of regions corresponding to the distinct types of regions of the photo-mask;

instructions for determining a first function corresponding to the first mask pattern, wherein the range of the first function has a cardinality that is greater than the number of distinct types of regions of the first mask pattern, and wherein the domain of the first function corresponds to the plane of the first mask pattern; and

instructions for generating a second function based, at least in part, on the first function, wherein the second function corresponds to a second mask pattern.

41. A photo-mask for use in a photolithographic process, wherein the photo-mask has a plurality of distinct types of regions having distinct optical properties, and wherein a mask pattern to which the photo-mask corresponds is determined in a process including the operations of:

providing a first mask pattern that includes a plurality of distinct types of regions corresponding to the distinct types of regions of the photo-mask;

determining a first function corresponding to the first mask pattern, wherein the range of the first function has a cardinality that is greater than the number of distinct types of regions of the first mask pattern, and wherein the domain of the first function corresponds to the plane of the first mask pattern; and

generating a second function based, at least in part, on the first function, wherein the second function corresponds to a second mask pattern.

42. A semiconductor wafer, wherein the semiconductor wafer is produced in a photo-lithographic process that includes a photo-mask, wherein the photo-mask has a plurality of distinct types of regions having distinct optical properties, and wherein a mask pattern to which the photo-mask corresponds is determined in a process including the operations of:

providing a first mask pattern that includes a plurality of distinct types of regions corresponding to the distinct types of regions of the photo-mask;

determining a first function corresponding to the first mask pattern, wherein the range of the first function has a cardinality that is greater than the number of distinct types of regions of the first mask pattern, and wherein the domain of the first function corresponds to the plane of the first mask pattern; and

generating a second function based, at least in part, on the first function, wherein the second function corresponds to a second mask pattern.