Optimized photomasks for photolithography

• US 7,571,423 B2
• Filed: 09/12/2005
• Issued: 08/04/2009
• Est. Priority Date: 04/06/2003
• Status: Active Grant

• Current Assignee: Dino Technology Acquisition LLC
• Original Assignee: Luminescent Technologies, Inc. (KLA Corporation)
• Inventors: Osher, Stanley, Abrams, Daniel, Peng, Danping
• Primary Examiner(s): Levin; Naum B
• Application Number:
  US11/225,378
• Publication Number:
  US 20070011647A1
• Time in Patent Office: 1,422 Days
• Field of Search: 716 19- 21, 703/2, 382144-145, 430/5
• US Class Current: 716/50
• 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 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

1. A computer apparatus, 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, the at least one program module including;

instructions for providing a function having input values corresponding to an area of a photomask and output values indicating the position of a contour of a photomask pattern on the photomask, wherein the photomask pattern includes a number of different regions having different optical properties, the function results in at least three different output values over the area of the photomask, and the number of the different output values over the area of the photomask is greater than the number of different regions having the different optical properties;

instructions for evaluating the function over at least a portion of the area of the photomask; and

instructions for storing the output values from the function to represent the position of the contour of the photomask pattern over the portion of the area of the photomask, wherein the contour of the photomask pattern is adapted for use in subsequent fabrication of the photomask,

wherein the instructions for storing the output values further include instructions for storing selected output values based on a distance to the contour of the photomask pattern.

2. The computer apparatus of claim 1, wherein the at least one program module includes instructions for receiving the photomask pattern in a format selected from the group consisting of GDSII and OASIS.

3. The computer apparatus of claim 1, wherein the function includes a level set function.

4. The computer apparatus of claim 1, wherein the function includes a distance function.

5. The computer apparatus of claim 1, wherein the instructions for evaluating the function over at least a portion of the area of the photomask include instructions for evaluating the function over a grid of m points across the portion of the area of the photomask.

6. The computer apparatus of claim 1, wherein the instructions for storing the output values include instructions for storing only selected output values based on a distance to the contour of the photomask pattern.

7. A computer-program product for use in conjunction with a computer system, the computer-program product comprising a computer-readable storage device and a computer-program mechanism embedded therein for configuring the computer system for evaluating a function, the computer-program mechanism including:

instructions for providing a function having input values corresponding to an area of a photomask and output values indicating the position of a contour of a photomask pattern on the photomask, wherein the photomask pattern includes a number of different regions having different optical properties, the function results in at least three different output values over the area of the photomask, and the number of the different output values over the area of the photomask is greater than the number of different regions having the different optical properties;

instructions for evaluating the function over at least a portion of the area of the photomask; and

instructions for storing the output values from the function to represent the position of the contour of the photomask pattern over the portion of the area of the photomask, wherein the contour of the photomask pattern is adapted for use in subsequent fabrication of the photomask,

wherein the instructions for storing the output values further include instructions for storing selected output values based on a distance to the contour of the photomask pattern.

8. The computer-program product of claim 7, wherein the at least one program module includes instructions for receiving the photomask pattern in a format selected from the group consisting of GDSII and OASIS.

9. The computer-program product of claim 7, wherein the function includes a level set function.

10. The computer-program product of claim 7, wherein the function includes a distance function.

11. The computer-program product of claim 7, wherein the instructions for evaluating the function over at least a portion of the area of the photomask include instructions for evaluating the function over a grid of m points across the portion of the area of the photomask.

12. The computer-program product of claim 7, wherein the instructions for storing the output values include instructions for storing only selected output values based on a distance to the contour of the photomask pattern.

13. The computer-program product of claim 7:

wherein the different regions of the photomask pattern include at least a first region and a second region; and

wherein the first region is transmissive and the second region is non-transmissive.

14. The computer-program product of claim 13, wherein the function includes a level set function.

15. The computer-program product of claim 13, wherein the function includes a distance function.

16. The computer-program product of claim 13, wherein the instructions for evaluating the function over at least a portion of the area of the photomask include instructions for evaluating the function over a grid of m points across the portion of the area of the photomask.

17. The computer-program product of claim 13, wherein the instructions for storing the output values include instructions for storing only selected output values based on a distance to the contour of the photomask pattern.

18. The computer-program product of claim 13, wherein the instructions for storing the output values include instructions for selectively storing only a portion of the output values.

19. The computer-program product of claim 18, wherein the function includes a distance function.