Continuous direct-write optical lithography

• US 7,295,362 B2
• Filed: 09/14/2004
• Issued: 11/13/2007
• Est. Priority Date: 08/24/2002
• Status: Active Grant

• Current Assignee: Chime Ball Technology Co., Ltd.
• Original Assignee: Maskless Lithography, Inc.
• Inventors: Meisburger, William Daniel
• Primary Examiner(s): Mack; Ricky
• Assistant Examiner(s): Thomas; Brandi
• Application Number:
  US10/941,969
• Publication Number:
  US 20050041229A1
• Time in Patent Office: 1,155 Days
• Field of Search: 359/290, 359/291, 359/292, 359/298, 359/224, 355/35, 355/44, 355/66, 355/67, 355/71
• US Class Current: 359/290
• CPC Class Codes: G03F 7/70216 Mask projection systems
• CPC Class Codes: G03F 7/70275 Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems
• CPC Class Codes: G03F 7/70283 Mask effects on the imaging process
• 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 7/70383 Direct write, i.e. pattern is written directly without the use of a mask by one or multiple beams maskless lithography using a programmable mask G03F7/70291
• CPC Class Codes: G03F 7/70466 Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature stitching G03F7/70475
• CPC Class Codes: G03F 7/70508 Data handling in all parts of the microlithographic apparatus, e.g. handling pattern data for addressable masks or data transfer to or from different components within the exposure apparatus
• CPC Class Codes: G03F 7/70558 Dose control, i.e. achievement of a desired dose

Abstract

An optical lithography system comprises a light source, a spatial light modulator, imaging optics and means for continuously moving a photosensitive substrate relative to the spatial light modulator. The spatial light modulator comprises at least one array of individually switchable elements. The spatial light modulator is continuously illuminated and an image of the spatial light modulator is continuously projected on the substrate; consequently, the image is constantly moving across the surface of the substrate. While the image is moving across the surface, elements of the spatial light modulator are switched such that a pixel on the surface of the substrate receives, in serial, doses of energy from multiple elements of the spatial light modulator, thus forming a latent image on the substrate surface. The imaging optics is configured to project a blurred image of the spatial light modulator on the substrate, enabling sub-pixel resolution feature edge placement.

Claims

1. A lithographic method, comprising the steps of:

illuminating a spatial light modulator, said spatial light modulator comprising an area array of individually switchable elements;

projecting an image of said spatial light modulator on a photosensitive surface of a substrate;

moving said image across said surface of said substrate;

while said image is moving, switching said elements of said spatial light modulator, whereby a pixel on said photosensitive surface receives, in serial, doses of energy from multiple elements of said spatial light modulator, thus forming a latent image on said surface; and

blurring said image, where said blurring enables sub-pixel resolution feature edge placement.

2. A lithographic method as in claim 1, wherein said blurring comprises defocusing said image.

3. A lithographic method as in claim 1, wherein said blurring is implemented by a diffuser positioned between said spatial light modulator and said substrate.

4. A lithographic method as in claim 1, wherein said blurring comprises adjusting the numerical aperture of projection optics positioned between said spatial light modulator and said substrate.

5. A lithographic method as in claim 1, wherein said blurring is implemented by a microlens array positioned between said spatial light modulator and said substrate.

6. A lithographic method as in claim 1, wherein said illuminating step comprises continuously illuminating said spatial light modulator.

7. A lithographic method as in claim 1, wherein said illuminating step is implemented by a lamp system comprising an arc lamp.

8. A lithographic method as in claim 1, wherein said illuminating step is implemented by a laser.

9. A lithographic method as in claim 8, wherein said laser is a continuous laser.

10. A lithographic method as in claim 8, wherein said laser is a quasi-continuous laser.

11. A lithographic method as in claim 1, wherein, during formation of said latent image, said projecting step comprises continuously projecting said image of said spatial light modulator on said photosensitive surface of said substrate.

12. A lithographic method as in claim 1, wherein said projecting step is implemented by a telecentric projection lens system.

13. A lithographic method as in claim 1, wherein said spatial light modulator comprises a digital micro-mirror device.

14. A lithographic method as in claim 1, wherein said moving step is implemented by a stage.

15. A lithographic method as in claim 14, wherein said spatial light modulator is carried on said stage.

16. A lithographic method as in claim 15, wherein projection optics is carried on said stage.

17. A lithographic method as in claim 14, wherein said substrate is carried on said stage.

18. A lithographic method as in claim 1, wherein said substrate is a flexible film substrate.

19. A lithographic method as in claim 18, wherein said moving step is implemented by rotatable, spaced apart, axially parallel film drums, said flexible film substrate being wrapped around and tensioned between said drums.

20. A lithographic method as in claim 18, wherein said moving step is further implemented by a stage, said spatial light modulator being carried on said stage.

21. A lithographic method as in claim 20, wherein projection optics is carried on said stage.

22. A lithographic method as in claim 20, wherein said stage and said substrate move in orthogonal directions to each other.

50. A lithographic method as in claim 1, wherein said individually switchable elements are configured in rows and the direction of movement of said image across the surface of said substrate is perpendicular to said rows of elements.

51. A lithographic method as in claim 1, wherein said moving step includes moving said image across said surface of said substrate in a serpentine manner.

23. A lithographic method for a substrate, comprising the steps of:

positioning a substrate below a spatial light modulator;

illuminating said spatial light modulator, said spatial light modulator being positioned on a stage, said stage being controlled to move in a patterning direction during exposure of said substrate, said spatial light modulator comprising an area array of individually switchable elements, said elements having pitch p, as measured in said patterning direction;

moving said spatial light modulator in said patterning direction at speed v over said substrate;

while said spatial light modulator is moving, continuously projecting a blurred image of said spatial light modulator on said substrate; and

while said blurred image is being projected, switching said spatial light modulator at times separated by a time interval

T=p/v

such that a pixel on a photosensitive surface of said substrate receives, in serial, doses of energy from multiple elements of said spatial light modulator, where said blurred image enables sub-pixel resolution feature edge placement.

24. A lithographic method for a flexible film substrate, comprising the steps of:

moving said flexible film substrate in a patterning direction at speed v;

continuously illuminating a spatial light modulator, said spatial light modulator comprising an area array of individually switchable elements, said elements having pitch p, as measured in said patterning direction;

while said flexible film substrate is moving, illuminating said substrate with an image, at magnification M, of said continuously illuminated spatial light modulator; and

while said substrate is being illuminated, switching said spatial light modulator at times separated by a time interval

T=pM/v

such that a pixel on a photosensitive surface of said substrate receives, in serial, doses of energy from multiple elements of said spatial light modulator;

wherein said moving of said substrate is implemented by rotatable, spaced apart, axially parallel film drums, said substrate being wound around and tensioned between said drums.

25. A lithographic method as in claim 24, wherein said image, at magnification M, of said continuously illuminated spatial light modulator is blurred.

61. A lithographic method as in claim 24, wherein said second illuminating step continuously illuminates said substrate with an image, at magnification M, of said continuously illuminated spatial light modulator.

26. A lithographic method, comprising the steps of:

(a) positioning a substrate below a spatial light modulator;

(b) illuminating said spatial light modulator, said spatial light modulator comprising an area array of individually switchable elements;

(c) projecting a blurred image, at magnification M, of said spatial light modulator on a photosensitive surface of said substrate;

(d) moving said image in a patterning direction at speed v across said photosensitive surface;

(e) while said image is moving, switching said spatial light modulator after a time interval of

T=pM/v

where p is the pitch of said elements, as measured in said patterning direction; and

(f) repeating step (e), such that pixels on said substrate receive, in serial, doses of energy from multiple elements of said spatial light modulator, until a desired latent image is formed on said photosensitive surface.

62. A lithographic method as in claim 26, wherein said projecting step continuously projects a blurred image, at magnification M, of said spatial light modulator on a photosensitive surface of said substrate.

27. A lithographic method, comprising the steps of:

illuminating a spatial light modulator using a light source, said spatial light modulator comprising an area array of individually switchable elements;

projecting an image of said spatial light modulator on a photosensitive surface of a substrate;

moving said image across said surface of said substrate;

while said image is moving, switching said elements of said spatial light modulator at times separated by a time interval;

controlling passage of light along a light path, said light path going from said light source to said spatial light modulator and ending at said substrate; and

blurring said image, where said blurring enables sub-pixel resolution feature edge placement.

28. A lithographic method as in claim 27, wherein passage of light is controlled by a light switching mechanism, said mechanism being operated at the same frequency as, and out of phase with, said elements of said spatial light modulator.

29. A lithographic method as in claim 28, wherein all of said elements of said spatial light modulator are in an off state every other time interval and said switching mechanism is in an off state every other time interval.

30. A lithographic method as in claim 27, wherein passage of light is allowed for a time span which is a fraction of said switching time interval, said image moving a single pixel'"'"'s length on said substrate surface during said time span.

31. A lithographic method as in claim 30, wherein said time span is a submultiple of said switching time interval.

32. A lithographic method, comprising the steps of:

illuminating a spatial light modulator using a light source, said spatial light modulator comprising an area array of individually switchable elements;

projecting an image of said spatial light modulator on a photosensitive surface of a substrate;

moving said image across said surface of said substrate;

while said image is moving, switching said elements of said spatial light modulator at times separated by a time interval; and

controlling passage of light along a light path, said light path going from said light source to said spatial light modulator and ending at said substrate;

wherein passage of light is controlled by a light switching mechanism, said mechanism being operated at the same frequency as, and out of phase with, said elements of said spatial light modulator.

33. A lithographic method as in claim 32, wherein all of said elements of said spatial light modulator are in an off state every other time interval and said switching mechanism is in an off state every other time interval.

34. A lithographic method, comprising the steps of:

illuminating a spatial light modulator using a light source, said spatial light modulator comprising an area array of individually switchable elements;

projecting an image of said spatial light modulator on a photosensitive surface of a substrate;

moving said image across said surface of said substrate;

while said image is moving, switching said elements of said spatial light modulator at times separated by a time interval; and

controlling passage of light along a light path, said light path going from said light source to said spatial light modulator and ending at said substrate;

wherein passage of light is allowed for a time span which is a fraction of said switching time interval, said image moving a single pixel'"'"'s length on said substrate surface during said time span.

35. A lithographic method as in claim 34, wherein said time span is a submultiple of said switching time interval.

36. A lithographic method, comprising the steps of:

illuminating a plurality of spatial light modulators using a light source, each of said plurality of spatial light modulators comprising an area array of individually switchable elements;

projecting images of each of said plurality of spatial light modulators on a photosensitive surface of a substrate;

moving said images across said surface of said substrate; and

while said images are moving, switching said elements of said plurality of spatial light modulators, whereby a pixel on said photosensitive surface receives, in serial, doses of energy from multiple elements of said plurality of spatial light modulators, thus forming a latent image on said surface; and

blurring said images, where said blurring enables sub-pixel resolution feature edge placement;

wherein at least two of said projected images simultaneously overlap on said substrate.

37. A lithographic method as in claim 36, wherein said spatial light modulators with overlapping projected images on said substrate are switched with the same frequency and are switched out of phase with each other.

38. A lithographic method as in claim 36, wherein said overlapping projected images are in register.

39. A lithographic method, comprising the steps of:

(a) positioning a substrate below a spatial light modulator;

(b) illuminating said spatial light modulator, said spatial light modulator comprising an area array of individually switchable elements;

(c) projecting an image, at magnification M, of said spatial light modulator on a photosensitive surface of said substrate;

(d) switching said elements of said spatial light modulator at times separated by a time interval T;

(e) while said elements are switching, moving said image in a patterning direction across said photosensitive surface at speed

v=npM/T

where p is the pitch of said elements, as measured in said patterning direction, and n is an integer; and

(f) controlling passage of light along a light path, said light path going from said light source to said spatial light modulator and ending at said substrate, where passage of light is controlled by a light switching mechanism, said mechanism being operated at the same frequency as said elements of said spatial light modulator and shifted out of phase with said elements of said spatial light modulator by a time shift T(1−

1/n).

40. A lithographic method as in claim 39, whereby pixels on said substrate receive, in serial, doses of energy from multiple elements of said spatial light modulator, until a desired latent image is formed on said photosensitive surface.

41. A lithographic method as in claim 39, further comprising blurring said image of said spatial light modulator.

42. A lithographic method as in claim 39, wherein all of said elements of said spatial light modulator are in an off state every other time interval and said switching mechanism is in an off state every other time interval.

43. A lithographic method, comprising the steps of:

(a) positioning a substrate below a spatial light modulator;

(b) illuminating said spatial light modulator, said spatial light modulator comprising an area array of individually switchable elements;

(c) projecting an image, at magnification M, of said spatial light modulator on a photosensitive surface of said substrate;

(d) switching said elements of said spatial light modulator at times separated by a time interval T;

(e) while said elements are switching, moving said image in a patterning direction across said photosensitive surface at speed

v=npM/T

where p is the pitch of said elements, as measured in said patterning direction, and n is a constant; and

(f) controlling passage of light along a light path, said light path going from said light source to said spatial light modulator and ending at said substrate, where passage of light is controlled by a light switching mechanism, said mechanism being operated to allow the passage of light for a time span T/n.

44. A lithographic method as in claim 43, further comprising repeating step (f), whereby pixels on said substrate receive, in serial, doses of energy from multiple elements of said spatial light modulator, until a desired latent image is formed on said photosensitive surface.

45. A lithographic method as in claim 43, further comprising blurring said image of said spatial light modulator.

46. A lithographic method as in claim 43, wherein said light switching mechanism is operated to allow the passage of light for one time span T/n per time interval T.

47. A lithographic method as in claim 43, wherein n is an integer.

48. A lithographic method, comprising the steps of:

illuminating a spatial light modulator using a light source, said spatial light modulator comprising an area array of individually switchable elements;

projecting an image of said spatial light modulator on a photosensitive surface of a substrate;

moving said image across said surface of said substrate;

while said image is moving, switching said elements of said spatial light modulator; and

blurring said image, where said blurring enables sub-pixel resolution feature edge placement;

wherein the direction of movement of said image is not parallel to columns of pixels in said projected image of said spatial light modulator.

49. A lithographic method as in claim 48 wherein said elements of said spatial light modulator are switched at times separated by a time interval, whereby pixels on said substrate receive, in serial, doses of energy from multiple elements of said spatial light modulator, until a desired latent image is formed on said photosensitive surface.

52. A lithographic method, comprising the steps of:

illuminating a plurality of spatial light modulators, each of said plurality of spatial light modulators comprising an area array of individually switchable elements;

projecting an image of said plurality of spatial light modulators on a photosensitive surface of a substrate;

moving said image across said surface of said substrate;

while said image is moving, switching said elements of said plurality of spatial light modulators, whereby a pixel on said photosensitive surface receives, in serial, doses of energy from multiple elements of said plurality of spatial light modulators, thus forming a latent image on said surface; and

blurring said image, where said blurring enables sub-pixel resolution feature edge placement.

53. A lithographic method as in claim 52, wherein each of said spatial light modulators exposes a swath of said photosensitive surface.

54. A lithographic method as in claim 52, wherein each of said spatial light modulators exposes a non-overlapping swath of said photosensitive surface.

55. A lithographic method as in claim 52, wherein said plurality of spatial light modulators are arranged in at least one row, said at least one row being perpendicular to the direction of movement of said image across the surface of said substrate.

56. A lithographic method as in claim 52, wherein said projecting step is implemented by a single projection lens system.

57. A lithographic method as in claim 52, wherein said projecting step is implemented by a multiplicity of projection lens systems.

58. A lithographic method as in claim 57, wherein said multiplicity of projection lens systems comprises a single projection lens system for each of said plurality of spatial light modulators.

59. A lithographic method as in claim 52, whereby a pixel on a photosensitive surface of said substrate receives, in serial, doses of energy from multiple elements of one of said plurality of spatial light modulators, thus forming a latent image on said surface.

60. A lithographic method as in claim 52, wherein said projecting step continuously projects an image of said plurality of spatial light modulators on a photosensitive surface of a substrate.