Method for facilitating automatic analysis of defect printability

• US 20040109601A1
• Filed: 12/06/2002
• Published: 06/10/2004
• Est. Priority Date: 12/06/2002
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Numerical Technologies Inc. (Synopsys Incorporated)
• Inventors: Pang, Linyong
• Granted Patent: US 8,111,898 B2
• Time in Patent Office: Days
• US Class Current: 382/149
• CPC Class Codes: G03F 1/84 Inspecting
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

Defect printability analysis in a mask or wafer requires the accurate identification of defect images and reference (i.e. defect-free) images, in particular for a die-to-die inspection mode. A method of automatically distinguishing a reference image from a defect image is provided. In this method, multiple images can be accessed and aligned. Then, a common area of the multiple images can be defined. At this point, a complexity of each of the images, as defined by the common area, can be computed. Advantageously, by comparing the complexity of the multiple images, the reference and defect images can be quickly and accurately designated. Specifically, the most complex image is designated the defect image because the defect image must describe the defect. Complexity can be computed using various techniques.

Claims

1. A method of automatically distinguishing a reference image from a defect image, the method comprising:

accessing multiple images;

aligning the multiple images;

defining a common area of the multiple images;

computing a complexity of each of the images, as defined by the common area; and

designating the reference and defect images by comparing the complexity of the multiple images.

2. The method of claim 1, wherein designating includes determining that the more complex image is the defect image.

3. The method of claim 1, wherein computing the complexity includes performing at least a portion of a spatial frequency transform.

4. The method of claim 3, wherein the spatial frequency transform includes generating a Fourier transform.

5. The method of claim 3, wherein the spatial frequency transform includes generating a JPEG file.

6. The method of claim 3, wherein the spatial frequency transform includes computing a fractal.

7. The method of claim 1, wherein computing the complexity includes performing a set of steps for partitioning.

8. The method of claim 1, wherein the multiple images are taken from a mask including optical proximity correction (OPC) features, and wherein computing the complexity includes simulating wafer images.

9. The method of claim 8, wherein designating includes determining that the simulated wafer image having more complex contours is associated with the defect image.

10. A program storage device readable by a machine, tangibly embodying a program of instructions executable by said machine to perform method steps to analyze a lithographic medium, the method comprising:

accessing multiple images of the lithographic medium;

aligning the multiple images;

defining a common area of the multiple images;

computing a complexity of each of the images, as defined by the common area; and

designating the reference and defect images by comparing the complexity of the multiple images.

11. The program storage device of claim 10, wherein designating includes determining that the more complex image is the defect image.

12. The program storage device of claim 10, wherein computing the complexity includes performing at least a portion of a spatial frequency transform.

13. The program storage device of claim 12, wherein the spatial frequency transform includes generating a Fourier transform.

14. The program storage device of claim 12, wherein the spatial frequency transform includes generating a JPEG file.

15. The program storage device of claim 12, wherein the spatial frequency transform includes computing a fractal.

16. The program storage device of claim 10, wherein computing the complexity includes performing a set of steps for partitioning.

17. The program storage device of claim 10, wherein the lithographic medium is a mask including optical proximity correction (OPC) features, and wherein computing the complexity includes simulating wafer images.

18. The program storage device of claim 17, wherein designating includes determining that the simulated wafer image having more complex contours is associated with the defect image.

19. A computer program product comprising:

a computer usable medium having a computer readable program code embodied therein for causing a computer to analyze a lithographic medium for defects, the computer readable program code comprising;

computer readable program code that accesses multiple images of the lithographic medium;

computer readable program code that aligns the multiple images;

computer readable program code that defines a common area of the multiple images;

computer readable program code that computes a complexity of each of the images, as defined by the common area; and

computer readable program code that automatically designates reference and defect images by comparing the complexity of the multiple images.

20. The computer program product of claim 19, wherein the computer readable program code that designates includes computer readable program code that determines the more complex image is the defect image.

21. The computer program product of claim 19, wherein the computer readable program code that computes the complexity includes computer readable program code that performs at least a portion of a spatial frequency transform.

22. The computer program product of claim 21, wherein the computer readable program code that performs includes computer readable program code that generates a Fourier transform.

23. The computer program product of claim 21, wherein the computer readable program code that performs includes computer readable program code that generates a JPEG file.

24. The computer program product of claim 21, wherein the computer readable program code that performs includes computer readable program code that computes a fractal.

25. The computer program product of claim 19, wherein the computer readable program code that computes the complexity includes computer readable program code that performs a set of steps for partitioning.

26. The computer program product of claim 19, wherein the lithographic medium is a mask including optical proximity correction (OPC) features, and wherein computer readable program code that computes the complexity includes computer readable program code that simulates wafer images.

27. The computer program product of claim 26, wherein the computer readable program code that designates includes computer readable program code that determines the simulated wafer image having more complex contours is associated with a defect image.

28. A system for analyzing a lithographic medium for defects, the system comprising:

means for accessing multiple images of the lithographic medium;

means for aligning the multiple images;

means for defining a common area of the multiple images;

means for computing a complexity of each of the images, as defined by the common area; and

means for designating the reference and defect images by comparing the complexity of the multiple images.

29. The system of claim 28, wherein the lithographic medium is a mask.

30. The system of claim 28, wherein the lithographic medium is a wafer.