Spatial light modulator as source module for DUV wavefront sensor

• US 20060001890A1
• Filed: 07/02/2004
• Published: 01/05/2006
• Est. Priority Date: 07/02/2004
• Status: Abandoned Application

• Current Assignee: ASML Holding NV
• Original Assignee: ASML Holding NV
• Inventors: Poultney, Sherman K.
• Application Number:
  US10/882,295
• Publication Number:
  US 20060001890A1
• Time in Patent Office: Days
• US Class Current: 356/521
• CPC Class Codes: G01J 9/0215 by shearing interferometric methods
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G03F 7/706 Aberration measurement

Abstract

A wavefront measurement system with a source of electromagnetic radiation and an illumination system that directs the electromagnetic radiation to a spatial light modulator to produce a diffraction pattern. A projection optical system projects an image of the spatial light modulator onto an image plane. A shearing grating is in the image plane. A detector receives a fringe pattern from the image plane. The spatial light modulator can generate a non-linear phase variation across it to scan the diffraction pattern across a pupil of the projection optical system. The spatial light modulator forms a synthetic grating. The spatial light modulator can be a transmissive-type or a reflective-type modulator. Pixels of the spatial light modulator form rulings of a synthetic grating that can have random variations of transmission and/or angular orientation within each ruling. The spatial light modulator can simulate lateral movement of the synthetic grating, or form a synthetic grating with different orientations of its rulings.

Claims

1. A wavefront measurement system comprising:

a source of electromagnetic radiation;

an illumination system that directs the electromagnetic radiation to a spatial light modulator that produces a diffraction pattern;

a projection optical system that projects an image of the spatial light modulator onto an image plane;

a shearing grating in the image plane; and

a detector that receives a fringe pattern from the image plane.

2. The system of claim 1, wherein the spatial light modulator generates a non-linear phase variation across it to scan the diffraction pattern across a pupil of the projection optical system.

3. The system of claim 1, wherein the spatial light modulator scans the diffraction pattern across a pupil of the projection optical system.

4. The system of claim 1, wherein the diffraction pattern is dynamically scanned across a pupil of the projection optical system.

5. The system of claim 1, wherein the detector is located in a plane that is optically conjugate with a pupil of the projection optical system.

6. The system of claim 1, wherein the spatial light modulator forms a synthetic grating.

7. The system of claim 1, wherein spatial light modulator is a transmissive-type modulator.

8. The system of claim 1, wherein spatial light modulator is a reflective-type modulator.

9. The system of claim 1, wherein pixels of the spatial light modulator form rulings of a synthetic grating that have random variations of transmission within each ruling.

10. The system of claim 1, wherein pixels of the spatial light modulator form rulings of a synthetic grating that have random variations of angular orientation within each ruling.

11. The system of claim 1, wherein the spatial light modulator forms a synthetic grating, and wherein the spatial light modulator is adapted for simulating lateral movement of the synthetic grating.

12. The system of claim 1, wherein the spatial light modulator forms a synthetic grating having a plurality of possible orientations of its rulings.

13. A wavefront measurement system comprising:

an illumination system that delivers electromagnetic radiation to an object plane;

a spatial light modulator in the object plane that generates a diffracted beam of the electromagnetic radiation;

a projection optical system that projects the beam onto an image plane; and

a detector that receives a fringe pattern of the beam from the image plane.

14. The system of claim 13, wherein the spatial light modulator generates a non-linear phase variation across it to scan the diffracted beam across a pupil of the projection optical system.

15. The system of claim 13, wherein the spatial light modulator scans the diffracted beam across a pupil of the projection optical system.

16. The system of claim 13, wherein the diffracted beam is dynamically scanned across a pupil of the projection optical system.

17. The system of claim 13, wherein the detector is located in a plane that is optically conjugate with a pupil of the projection optical system.

18. The system of claim 13, wherein the spatial light modulator forms a synthetic grating.

19. The system of claim 13, wherein spatial light modulator is a transmissive-type modulator.

20. The system of claim 13, wherein spatial light modulator is a reflective-type modulator.

21. The system of claim 13, wherein pixels of the spatial light modulator form rulings of a synthetic grating that have random variations of transmission within each ruling.

22. The system of claim 13, wherein pixels of the spatial light modulator form rulings of a synthetic grating that have random variations of angular orientation within each ruling.

23. The system of claim 13, wherein the spatial light modulator forms a synthetic grating, and wherein the spatial light modulator is adapted for simulating lateral movement of the synthetic grating.

24. The system of claim 13, wherein the spatial light modulator forms a synthetic grating having a plurality of possible orientations of its rulings.

25. The system of claim 13, wherein the spatial light modulator forms a synthetic grating that changes its pitch to match a pitch of a grating in an image plane of the projection optical system.

26. The system of claim 13, wherein the spatial light modulator forms a synthetic grating that changes its orientation to match an orientation of a grating in an image plane of the projection optical system.

27. A method of measuring a wavefront of an optical system comprising:

generating electromagnetic radiation at a source;

delivering the electromagnetic radiation to a spatial light modulator;

forming a diffraction pattern at the spatial light modulator;

scanning the diffraction pattern across a pupil of an optical system;

receiving an image of the source; and

determining wavefront parameters from the image.

28. The method of claim 27, further comprising scanning the diffraction pattern across the pupil.

29. The method of claim 27, wherein the forming step comprises generating a non-linear phase variation across the spatial light modulator to scan the diffraction pattern across the pupil.

30. The method of claim 27, wherein the detector is located in a plane that is optically conjugate with the pupil.

31. The method of claim 27, further comprising forming a synthetic grating using the spatial light modulator.

32. The method of claim 30, further comprising changing a pitch of the synthetic grating to match a pitch of a grating in an image plane of the optical system.

33. The method of claim 30, further comprising changing an orientation of the synthetic grating to match an orientation of a grating in an image plane of the projection optical system.

34. The method of claim 27, wherein spatial light modulator is a transmissive-type modulator.

35. The method of claim 27, wherein spatial light modulator is a reflective-type modulator.

36. The method of claim 27, wherein the forming step comprises forming rulings of a synthetic grating that have random variations of transmission within each ruling.

37. The method of claim 27, wherein the forming step comprises forming rulings of a synthetic grating that have random variations of angular orientation within each ruling.

38. The method of claim 27, wherein the forming step comprises forming rulings of a synthetic grating, and wherein the forming step comprises simulating lateral movement of the synthetic grating.

39. The method of claim 27, wherein the forming step comprises forming a synthetic grating having a plurality of possible orientations of its rulings.

40. A method of measuring a wavefront of a projection optical system comprising:

(1) simulating a synthetic grating using the spatial light modulator;

(2) delivering electromagnetic radiation to a spatial light modulator positioned at an object plane of the projection optical system so as to generate a diffracted beam directed at the projection optical system;

(3) positioning a detector below an image plane of the projection optical system;

(4) receiving a fringe pattern of the diffracted beam at the detector; and

(5) calculating wavefront aberrations from the fringe pattern.