System, Masks, and Methods for Photomasks Optimized with Approximate and Accurate Merit Functions

• US 20070186206A1
• Filed: 10/06/2006
• Published: 08/09/2007
• Est. Priority Date: 10/06/2005
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Luminescent Technologies, Inc. (KLA Corporation)
• Inventors: Abrams, Daniel, Peng, Danping
• Granted Patent: US 7,703,049 B2
• Time in Patent Office: Days
• US Class Current: 716/52
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G06F 2119/18 Manufacturability analysis or optimisation for manufacturability
• CPC Class Codes: G06F 30/39 Circuit design at the physical level physical level design for reconfigurable circuits G06F30/347
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

Photomask patterns are represented using contours defined by mask 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. An accurate, slower merit function may be used to determine adjustment parameters for a faster, approximate merit function. The faster merit function may be used for iteration and adjusted based on the adjustment parameters.

Claims

1. A method, comprising:

evaluating a first merit function for a first pattern;

evaluating a second merit function for the first pattern;

determining adjustment parameters between the first merit function and the second merit function for the first pattern;

iteratively modifying the first pattern based, at least in part, on the second merit function and the adjustment parameters for the first pattern.

2. The method of claim 1, wherein the first merit function is slower and more accurate than the second merit function.

3. The method of claim 1, wherein the adjustment parameters are based, at least in part, upon a difference between the results obtained by the first merit function and the results obtained by the second merit function.

4. The method of claim 1, wherein the adjustment parameters are determined in part by the results of an experiment in a fab;

5. The method of claim 1, further comprising selecting a modified pattern to be used as an optimized pattern for a target pattern based on whether a threshold has been met, wherein the threshold is based, at least in part, upon the second merit function.

6. The method of claim 1, wherein the first pattern is represented as a function with a plurality of values across an area of a photomask.

7. The method of claim 1, wherein the function is a distance function.

8. The method of claim 1, wherein the first pattern is represented as a plurality of pixels across an area of a photomask.

9. A method, comprising:

providing a first photomask pattern;

dividing the photomask pattern into blocks;

for each block,

evaluating a first merit function for a pattern in the block;

evaluating a second merit function for a pattern in the block;

determining a adjustment parameters between the first merit function and the second merit function for the pattern in the block;

iteratively modifying the pattern in the block based, at least in part, on the second merit function and the adjustment parameters for the pattern.

10. A method, comprising:

evaluating a first forward model for a first pattern;

evaluating a second forward model for the first pattern;

determining adjustment parameters between the first forward model and the second forward model for the first pattern;

iteratively modifying the first pattern based, at least in part, on the second forward model and the adjustment parameters for the first pattern.

11. The method of claim 10, wherein the first forward model is slower and more accurate than the second forward model.

12. The method of claim 10, wherein the adjustment parameters are based, at least in part, upon a difference between the results obtained by the first forward model and the results obtained by the second forward model.

13. The method of claim 10, further comprising selecting a modified pattern to be used as an optimized pattern for a target pattern based on whether a threshold has been met, wherein the threshold is based, at least in part, upon the second forward model.

14. A method, comprising:

providing a first photomask pattern;

dividing the photomask pattern into a plurality of blocks;

for each block in the plurality of blocks,

evaluating a first forward model for a pattern in the block;

evaluating a second forward model for a pattern in the block;

determining a adjustment parameters between the first forward model and the second forward model for the pattern in the block;

iteratively modifying the pattern in the block based, at least in part, on the second forward model and the adjustment parameters for the pattern.

15. 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, the computer-program mechanism including:

instructions for evaluating a first forward model for a first pattern;

instructions for evaluating a second forward model for the first pattern;

instructions for determining adjustment parameters between the first forward model and the second forward model for the first pattern;

instructions for iteratively modifying the first pattern based, at least in part, on the second forward model and the adjustment parameters for the first pattern.

16. 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, the computer-program mechanism including:

instructions for providing a first photomask pattern;

instructions for dividing the photomask pattern into a plurality of blocks;

for each block in the plurality of blocks,

instructions for evaluating a first forward model for a pattern in the block;

instructions for evaluating a second forward model for a pattern in the block;

instructions for determining a adjustment parameters between the first forward model and the second forward model for the pattern in the block;

instructions for iteratively modifying the pattern in the block based, at least in part, on the second forward model and the adjustment parameters for the pattern.

17. 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, the at least one program module including;

instructions for evaluating a first forward model for a first pattern;

instructions for evaluating a second forward model for the first pattern;

instructions for determining adjustment parameters between the first forward model and the second forward model for the first pattern;

instructions for iteratively modifying the first pattern based, at least in part, on the second forward model and the adjustment parameters for the first pattern.

18. 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, the at least one program module including;

instructions for providing a first photomask pattern;

instructions for dividing the photomask pattern into a plurality of blocks;

for each block in the plurality of blocks,

instructions for evaluating a first forward model for a pattern in the block;

instructions for evaluating a second forward model for a pattern in the block;

instructions for determining a adjustment parameters between the first forward model and the second forward model for the pattern in the block;

instructions for iteratively modifying the pattern in the block based, at least in part, on the second forward model and the adjustment parameters for the pattern.

19. A photo-mask for use in a photolithographic process, wherein a mask pattern to which the photo-mask corresponds is determined in a process including the operations of:

evaluating a first forward model for a first pattern;

evaluating a second forward model for the first pattern;

determining adjustment parameters between the first forward model and the second forward model for the first pattern;

iteratively modifying the first pattern based, at least in part, on the second forward model and the adjustment parameters for the first pattern.

20. A photo-mask for use in a photolithographic process, wherein a mask pattern to which the photo-mask corresponds is determined in a process including the operations of:

providing a first photomask pattern;

dividing the photomask pattern into a plurality of blocks;

for each block in the plurality of blocks,

evaluating a first forward model for a pattern in the block;

evaluating a second forward model for a pattern in the block;

determining a adjustment parameters between the first forward model and the second forward model for the pattern in the block;

iteratively modifying the pattern in the block based, at least in part, on the second forward model and the adjustment parameters for the pattern.

21. A semiconductor wafer, wherein the semiconductor wafer is produced in a photo-lithographic process that includes a photo-mask, and wherein a mask pattern to which the photo-mask corresponds is determined in a process including the operations of:

evaluating a first forward model for a first pattern;

evaluating a second forward model for the first pattern;

determining adjustment parameters between the first forward model and the second forward model for the first pattern;

iteratively modifying the first pattern based, at least in part, on the second forward model and the adjustment parameters for the first pattern.

22. A semiconductor wafer, wherein the semiconductor wafer is produced in a photo-lithographic process that includes a photo-mask, and wherein a mask pattern to which the photo-mask corresponds is determined in a process including the operations of:

providing a first photomask pattern;

dividing the photomask pattern into a plurality of blocks;

for each block in the plurality of blocks,

evaluating a first forward model for a pattern in the block;

evaluating a second forward model for a pattern in the block;

determining a adjustment parameters between the first forward model and the second forward model for the pattern in the block;

iteratively modifying the pattern in the block based, at least in part, on the second forward model and the adjustment parameters for the pattern.