Method and apparatus for self-referenced projection lens distortion mapping

• US 6,573,986 B2
• Filed: 04/13/2001
• Issued: 06/03/2003
• Est. Priority Date: 12/08/2000
• Status: Active Grant

• Current Assignee: Litel Instruments Incorporated
• Original Assignee: Litel Instruments Incorporated
• Inventors: Smith, Adlai, McArthur, Bruce, Hunter, Jr., Robert
• Primary Examiner(s): MAI, HUY KIM
• Application Number:
  US09/835,201
• Publication Number:
  US 20020071112A1
• Time in Patent Office: 781 Days
• Field of Search: 356/124, 356/124.5, 356/125, 356/126, 356/127, 356/399, 356/400, 356/401, 355/52, 355/53, 430/22, 430/30
• US Class Current: 356/124
• CPC Class Codes: G03F 7/70558 Dose control, i.e. achievement of a desired dose
• CPC Class Codes: G03F 7/706 Aberration measurement
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
• CPC Class Codes: Y10S 977/887 Nanoimprint lithography, i.e. nanostamp

Abstract

A projection lens distortion error map is created using standard overlay targets and a special numerical algorithm. A reticle including a 2-dimensional array of standard overlay targets is exposed several times onto a photoresist coated silicon wafer using a photolithographic stepper. After exposure, the overlay targets are measured for placement error using a conventional overlay metrology tool. The resulting overlay error data is then supplied to a software program that generates a lens distortion error map for the photolithographic projection system.

Claims

1. A method of determining intra-field distortion in a projection imaging tool, the method comprising:

exposing a reticle pattern onto a substrate with a recording media in a first position, wherein the reticle pattern includes at least two arrays of alignment attributes, the arrays of alignment attributes have features complementary to each other and the arrays have the same pitch and are offset from each other;

exposing the reticle pattern onto the substrate in a second position, wherein the reticle pattern in the second position overlaps the reticle pattern in the first position and is shifted in a desired direction by an amount that corresponds to the offset;

measuring positional offsets of the alignment attributes; and

determining a lens distortion map from the resulting positional offset.

2. A method as defined in claim 1, wherein the desired direction corresponds to an X direction.

3. A method as defined in claim 1, wherein the desired direction corresponds to a Y direction.

4. A method as defined in claim 1, further comprising:

exposing the reticle pattern in a third position on the substrate, wherein the third position and the first position are separated by a desired distance; and

exposing the reticle pattern in a fourth position on the substrate, wherein the fourth position overlaps the third position and is shifted in a second desired direction by an amount that corresponds to the offset.

5. A method as defined in claim 4, wherein the first desired direction corresponds to an X direction and the second desired direction corresponds to a Y direction.

6. A method as defined in claim 4, further comprising:

exposing a reticle pattern in a fifth position on the substrate, wherein the fifth position is separated from the first and third positions by a desired distance; and

exposing the reticle pattern in a sixth position on the substrate, wherein the sixth position overlaps the fifth position and is shifted in a third desired direction by an amount that corresponds to the offset.

7. A method as defined in claim 6, wherein the third desired direction corresponds to a rotation.

8. A method as defined in claim 1, wherein the substrate is a semiconductor surface.

9. A method as defined in claim 1, wherein the substrate is a silicon wafer.

10. A method as defined in claim 9, wherein the silicon wafer is a notched wafer.

11. A method as defined in claim 1, wherein the substrate is a flat panel display.

12. A method as defined in claim 1, wherein the substrate is a reticle.

13. A method as defined in claim 1, wherein the substrate is a photolithographic mask.

14. A method as defined in claim 1, wherein the substrate is an electronic recording media.

15. A method as defined in claim 1, wherein the projection imaging tool is used in a photolithographic stepper system.

16. A method as defined in claim 1, wherein the projection imaging tool is used in a photolithographic scanner system.

17. A method as defined in claim 1, wherein the projection imaging tool is used in an electronic beam imaging system.

18. A method as defined in claim 1, wherein the projection imaging tool is used in a direct write tool.

19. A method as defined in claim 1, wherein the projection imaging tool is used in a SCALPEL tool.

20. A method as defined in claim 1, wherein the projection imaging tool is used in an extreme ultra-violet photolithographic tool.

21. A method as defined in claim 1, wherein the projection imaging tool is used in a x-ray imaging system.

22. A method as defined in claim 1, wherein the recording media is a positive resist material.

23. A method as defined in claim 1, wherein the recording media is a negative resist material.

24. A method as defined in claim 1, wherein the recording media is an electronic CCD.

25. A method as defined in claim 1, wherein the recording media is a diode array.

26. A method as defined in claim 1, wherein the recording media is a liquid crystal material.

27. A method as defined in claim 1, wherein the recording material is an optically sensitive material.

28. A method as defined in claim 1, wherein exposing the reticle pattern is at an exposure level below the minimum exposure dose of the recording media.

29. A method as defined in claim 28, wherein the reticle pattern is exposed a desired number of times.

30. A method of determining intra-field distortion in a projection imaging tool, the method comprising:

exposing a reticle pattern onto a substrate with a recording media in a first position, wherein the reticle pattern includes at least two arrays of alignment attributes, the arrays of alignment attributes have features complementary to each other and the arrays have the same pitch and are offset from each other;

exposing the reticle pattern onto the substrate in a second position, wherein the first and second positions are separated by a desired distance;

exposing the reticle pattern onto the substrate in a third position, wherein the reticle pattern in the third position overlaps the reticle pattern in the first position and is shifted in a first desired direction by an amount that corresponds to the offset;

exposing the reticle pattern onto the substrate in a fourth position, wherein the reticle pattern in the fourth position overlaps the reticle pattern in the second position and is shifted in a second desired direction by an amount that corresponds to the offset;

measuring positional offsets of the alignment attributes; and

determining a lens distortion map from the resulting positional offset.

31. A method as defined in claim 30, wherein the first desired direction corresponds to an X direction.

32. A method as defined in claim 30, wherein the second desired direction corresponds to a Y direction.

33. A method as defined in claim 30, further comprising:

exposing a reticle pattern onto the substrate in a fifth position; and

exposing a reticle pattern onto the substrate in a sixth position, wherein the sixth position overlaps the fifth position and is rotated by a desired amount with respect to the fifth position.

34. A method as defined in claim 33, wherein the rotation is 90 degrees.

35. A reticle for determining intra-field distortion in a projection imaging tool, the reticle comprising:

a first set of reticle alignment attributes in a pattern with a constant pitch selected to indicate the intra field distortion of a projection system; and

a second set of reticle alignment attributes that are complementary to the first set of alignment attributes, the second set of alignment attributes in a pattern with the same pitch as the first set of alignment attributes and offset from the first set of alignment attributes by a desired amount.

36. A reticle as defined in claim 35, wherein a first instance of the second set of alignment attributes is offset from the first set of alignment attributes in a first direction, and a second instance of the second alignment attributes is offset from the first set of alignment attributes in a second direction that is distinct from the first direction.

37. A reticle as defined in claim 36, wherein the first and second direction are perpendicular to one another.

38. A reticle as defined in claim 36, wherein the alignment attributes are in a regular rectangular grid pattern.

39. A reticular as defined in claim 38, wherein the first direction is parallel to the axis of the rectangular grid.

40. A reticle as defined in claim 35, further comprising a partially reflecting dielectric coating.

41. A reticle as defined in claim 35, further comprising an attenuated phase shift mask.

42. A projection imaging tool comprising:

means for exposing a reticle pattern onto a substrate with a recording media in a first position, wherein the reticle pattern includes at least two arrays of alignment attributes such that the arrays of alignment attributes have features complementary to each other and the arrays have the same pitch and are offset from each other;

means for exposing the reticle pattern onto the substrate in a second position, wherein the reticle pattern in the second position overlaps the reticle pattern in the first position and is shifted in a desired direction by an amount that corresponds to the offset;

means for measuring positional offsets of the alignment attributes; and

means for determining a lens distortion map from the resulting positional offset.

43. A reticle for determining intra-field distortion in a projection imaging tool, the reticle comprising:

means for positioning a first set of reticle alignment attributes arranged in a pattern with a constant pitch selected to indicate the intra field distortion of a projection system; and

means for positioning a second set of reticle alignment attributes that are complementary to the first set of alignment attributes, such that the second set of alignment attributes are arranged in a pattern with the same pitch as the first set of alignment attributes and are offset from the first set of alignment attributes by a desired amount.