Maskless photolithography for etching and deposition

• US 20030190536A1
• Filed: 06/25/2002
• Published: 10/09/2003
• Est. Priority Date: 06/27/2001
• Status: Active Grant

• Current Assignee: University of South Florida (State University System of Florida)
• Original Assignee: University of South Florida (State University System of Florida)
• Inventors: Fries, David P.
• Granted Patent: US 6,998,219 B2
• Time in Patent Office: Days
• US Class Current: 430/22
• CPC Class Codes: G03F 7/0041 providing an etching agent upon exposure G03F7/075 takes precedence; photolytic halogen compounds G03F7/0295
• CPC Class Codes: G03F 7/2002 with visible light or UV light, through an original having an opaque pattern on a transparent support, e.g. film printing, projection printing; by reflection of visible or UV light from an original such as a printed image
• CPC Class Codes: G03F 7/2043 with the production of a chemical active agent from a fluid, e.g. an etching agent; with meterial deposition from the fluid phase, e.g. contamination resists
• CPC Class Codes: G03F 7/2051 Exposure without an original mask, e.g. using a programmed deflection of a point source, by scanning, by drawing with a light beam, using an addressed light or corpuscular source G03F7/70 takes precedence
• 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 7/70341 Details of immersion lithography aspects, e.g. exposure media or control of immersion liquid supply chemical composition of immersion liquids G03F7/2041
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

The present invention relates to maskless photolithography using a patterned light generator for creating 2-D and 3-D patterns on objects using etching and deposition techniques. In an embodiment, the patterned light generator uses a micromirror array to direct pattern light on a target object. In an alternate embodiment, the patterned light generator uses a plasma display device to generate and direct patterned light onto a target object. Specifically, the invention provides a maskless photolithography system and method for photo stimulated etching of objects in a liquid solution, patterning glass, and photoselective metal deposition. For photo stimulated etching of objects in a liquid solution, the invention provides a system and method for immersing a substrate in an etchant solution, exposing the immersed substrate to patterned light, and etching the substrate according to the pattern of incident light. For patterning photoreactive glass, the invention provides a system and method for exposing photosensitive or photochromic glass, and washing the target glass with rinse and acid etchant solutions. For photoselective metal deposition, the invention provides a system and method for coating and rinsing a substrate prior to exposure exposing the substrate to a patterned light generator to activate areas corresponding to the incident light pattern, and plating the substrate in the area activated by the light after exposure. By providing a maskless pattern generator, the invention advantageously eliminates the problems associated with using masks for photo stimulated etching, patterning glass, and photoselective metal deposition.

Claims

1. A maskless photolithography system for photo stimulated etching of substrates in a liquid solution comprising:

a. a computer system for generating mask patterns and alignment instructions;

b. a maskless patterned light generator, radiating a patterned light beam, operably connected to and controllable by said computer system; and

c. an electrochemical bath for immersing the substrate, comprising an outer container, a etchant solution reactive with the substrate, an inner mount for affixing the substrate so that the substrate is fixedly immersed in said etchant solution and exposable to said patterned light beam, an anode electrically attached to the substrate, and a cathode immersed in said etchant solution and positioned so as not to make electrical contact with the substrate, wherein said anode and cathode are electrically connected to an ammeter;

wherein the immersed substrate is exposed to said patterned light beam, and said patterned light beam impinging on the immersed substrate causes said etchant solution to react with the immersed photoactive substrate, resulting in anisotropic etching of the immersed substrate according to said mask pattern of said patterned light beam.

2. The system of claim 1, wherein said maskless patterned light generator comprises:

a. an array of positionable micromirrors, wherein said micromirrors reflect light according to said mask patterns provided by said computer system;

b. an optical system for generating, collimating, and directing the light beam to said micromirror array; and

c. an optical system for further collimating the light beam reflected from said mirrors and directing said patterned light beam onto the immersed substrate and to create patterns on the immersed substrate corresponding to said mask patterns.

3. The system of claim 2, further comprising a computer controlled pattern modulation system, for varying the angular position of said micromirrors and duration of exposure of the immersed substrate, said modulation system altering the positioning of said micromirrors in response to instructions provided by said computer, whereby pixelation and stiction are reduced.

4. The system of claim 1, wherein said maskless patterned light generator comprises a plasma display having individually addressable pixels, operably connected to and controllable by said computer system, wherein said display generates said patterned light beam corresponding to said mask patterns provided by said computer system to expose the immersed substrate to said patterned light beam and to create patterns on the immersed substrate corresponding to said mask patterns.

5. The system of claim 1, further comprising a manually controlled alignment fixture for detachably mounting the outer container of said electrochemical bath, wherein said alignment fixture is movable in coplanar first and second dimensions, and in a third dimension direction substantially perpendicular to said first and second coplanar dimensions and substantially parallel to said patterned light beam;

said fixture providing three dimensional alignment of the immersed substrate beneath said patterned light beam, wherein said alignment fixture is moved in three dimensions in response to mechanical alignments directly provided by a user.

6. The system of claim 1, further comprising a computer controlled pattern alignment system, for providing electrical alignment of said patterns in coplanar first and second dimensions, wherein said pattern alignment system adjusts the alignment of said mask patterns in coplanar first and second dimensions in response to instructions provided by said computer according to said alignment information, so that said pattern is shifted in at least one coplanar direction.

7. The system of claim 1, further comprising an optical viewer to allow optical monitoring of positioning of the immersed substrate mounted in said alignment fixture by visually verifying that an image projected on the immersed substrate is properly aligned.

8. The system of claim 1, further comprising an optical filter, removably mounted in the light beam to selectively filter light impinging on the immersed substrate to prevent exposure of the immersed substrate during an alignment procedure.

9. The system of claim 1, wherein substrate comprises an n-type silicon (Si) substrate, p-type Si substrate, and gallium nitride (GaN) substrate.

10. A maskless photolithography system for patterning of photoreactive glass comprising:

a. a computer system for generating mask patterns and alignment instructions;

b. a maskless patterned light generator, radiating a patterned light beam, operably connected to and controllable by said computer system, and

c. a photoreactive glass substrate;

wherein said photoreactive glass substrate receives radiation from said patterned light beam, wherein said patterned light beam impinging on said photoreactive glass substrate creates patterns on said photoreactive glass substrate corresponding to said mask pattern of said patterned light beam.

11. The system of claim 10, further comprising an acid etchant, reactive with said photoreactive glass substrate, and applied as a coating to an exposed surface of said photoreactive glass substrate, wherein said photoreactive glass substrate, coated with said acid etchant, receives radiation from said patterned light beam, wherein said patterned light beam impinging on said photoreactive glass substrate causes anisotropic etching of said photoreactive glass substrate by said acid etchant in areas corresponding to incident said patterned light beam.

12. The system of claim 10, further comprising a circular alignment fixture, rotatably mounted on an axis for detachably affixing a plurality of said photoreactive glass substrates around the perimeter of said circular alignment fixture, wherein said fixture provides sequential exposure of a plurality of affixed said photoreactive glass substrates by rotating said fixture so that each of said photoreactive glass substrates is exposed to said patterned light beam.

13. The system of claim 10, further comprising an acid reservoir and a water reservoir, fluidically connected to and providing said acid etchant and rinse water through an acid nozzle and a water nozzle, respectively, positioned to sequentially apply etching acid and water rinse on said photoreactive glass substrates exposed to said patterned light beam.

14. The system of claim 10, wherein said maskless patterned light generator comprises:

a. an array of positionable micromirrors, wherein said micromirrors reflect light according to said mask patterns provided by said computer system;

b. an optical system for generating, collimating, and directing the light beam to said micromirror array;

c. an optical system for further collimating the light beam reflected from said mirrors and directing said patterned light beam onto said photoreactive glass substrate and to create patterns on said photoreactive glass substrate corresponding to said mask patterns.

15. The system of claim 14, further comprising a computer controlled pattern modulation system for varying the angular position of said micromirrors and duration of exposure of said photoreactive glass substrate, said modulation system altering the positioning of said micromirrors in response to instructions provided by said computer, whereby pixelation and stiction are reduced.

16. The system of claim 10, wherein said maskless patterned light generator comprises a plasma display having individually addressable pixels, operably connected to and controllable by said computer system, wherein said display generates said patterned light beam corresponding to said mask patterns provided by said computer system to expose said photoreactive glass substrate to said patterned light beam and to create patterns on said photoreactive glass substrate corresponding to said mask patterns.

17. The system of claim 10, further comprising a manually controlled alignment fixture for detachably mounting said photoreactive glass substrate, wherein said alignment fixture is movable in coplanar first and second dimensions, and in a third dimension direction substantially perpendicular to said first and second coplanar dimensions and substantially parallel to said patterned light beam;

said fixture providing three dimensional alignment of said photoreactive glass substrate beneath the light beam, wherein said alignment fixture is moved in three dimensions in response to mechanical alignments directly provided by a user.

18. The system of claim 10, further comprising a computer controlled pattern alignment system, for providing electrical alignment of said patterns in coplanar first and second dimensions, wherein said pattern alignment system adjusts the alignment of said mask patterns in coplanar first and second dimensions in response to instructions provided by said computer according to said alignment information, so that said pattern is shifted in at least one coplanar direction.

19. The system of claim 10, further comprising an optical viewer to allow optical monitoring of positioning of said photoreactive glass substrate mounted in said alignment fixture by visually verifying that an image projected on said photoreactive glass substrate is properly aligned.

20. The system of claim 10, further comprising an optical filter, removably mounted in the light beam to selectively filter light impinging on said photoreactive glass substrate to prevent exposure of said photoreactive glass substrate during an alignment procedure.

21. The system of claim 10, wherein said photoreactive glass is photochromic glass or a photosensitive glass.

22. The system of claim 10, wherein said system is used to create a temporary display in photoreactive glass.

23. A maskless photolithography system for photoselective metal deposition on a substrate comprising:

a. a computer system for generating mask patterns and alignment instructions;

b. a maskless patterned light generator, radiating a patterned light beam, operably connected to and controllable by said computer system;

c. a light activated catalytic coating bath to coat said substrate; and

d. a deposition bath for depositing metal on said substrate corresponding to regions activated by said patterned light beam;

wherein said substrate, coated with said light activated catalyst, receives radiation from said patterned light beam, wherein said patterned light beam impinging on said substrate creates activated regions on said substrate corresponding to said patterned light beam, wherein metal in solution is deposited on said activated regions of said substrate.

24. The system of claim 23, wherein said light activated catalytic coating bath comprises a solution of tin oxide.

25. The system of claim 23, further comprising a rinse bath to rinse said substrate after said substrate is coated with said light activated catalytic coating and before said substrate is exposed to said patterned light beam.

26. The system of claim 23, further comprising a surface coating bath to apply a coating to said substrate after said substrate receives said patterned light and before said metal is deposited on said substrate.

27. The system of claim 26, wherein said surface coating bath comprises palladium chloride.

28. The system of claim 23, wherein said deposition bath comprises an electro-less metal plating solution.

29. The system of claim 23, wherein said deposition bath comprises an electrolytic metal plating solution, an anode, electrically attached to said substrate, and a cathode, immersed in said metal plating solution and positioned so as not to make electrical contact with said substrate, wherein said anode is connected to the positive terminal of a voltage source, and said cathode is connected to a negative terminal of said voltage source, wherein said substrate is electrically biased to receive said metal plating.

30. The system of claim 23, wherein said maskless patterned light generator comprises:

a. an array of positionable micromirrors, wherein said micromirrors reflect light according to said mask patterns provided by said computer system;

b. an optical system for generating, collimating, and directing the light beam to said micromirror array; and

c. an optical system for further collimating the light beam reflected from said mirrors and directing said patterned light beam onto said substrate and to create patterns on said substrate corresponding to said mask patterns.

31. The system of claim 30, further comprising a computer controlled pattern modulation system, for varying the angular position of said micromirrors and duration of exposure of said substrate, said modulation system alters the positioning of said micromirrors in response to instructions provided by said computer, whereby pixelation and stiction are reduced.

32. The system of claim 23, wherein said maskless patterned light generator comprises a plasma display, having individually addressable pixels, operably connected to and controllable by said computer system, wherein said display generates said patterned light beam corresponding to said mask patterns provided by said computer system to expose said substrate to said patterned light beam and to create patterns on said substrate corresponding to said mask patterns.

33. The system of claim 23, further comprising a manually controlled alignment fixture for detachably mounting said substrate, wherein said alignment fixture is movable in coplanar first and second dimensions, and in a third dimension direction substantially perpendicular to said first and second coplanar dimensions and substantially parallel to said patterned light beam;

said fixture providing three dimensional alignment of a substrate beneath the light beam, wherein said alignment fixture is moved in three dimensions in response to mechanical alignments directly provided by a user.

34. The system of claim 23, further comprising a computer controlled pattern alignment system, for providing electrical alignment of said patterns in coplanar first and second dimensions, wherein said pattern alignment system adjusts the alignment of said mask patterns in coplanar first and second dimensions in response to instructions provided by said computer according to said alignment information, so that said pattern is shifted in at least one coplanar direction.

35. The system of claim 23, further comprising an optical viewer to allow optical monitoring of positioning of the substrate mounted in said alignment fixture by visually verifying that an image projected on the substrate is properly aligned.

36. The system of claim 23, further comprising an optical filter, removably mounted in the light beam to selectively filter light impinging on the substrate to prevent exposure of the substrate during an alignment procedure.

37. A method for maskless photolithography for photo stimulated etching of a substrate in a liquid solution comprising:

a. receiving mask pattern information corresponding to a desired pattern to be created on the substrate;

b. generating mask patterns based on received mask pattern information;

c. providing said mask patterns to patterned light generator;

d. generating a patterned light beam;

e. affixing the substrate to a mount, immersing the substrate affixed to said mount in an electrochemical bath comprising an outer container and a etchant solution reactive with the photoactive substrate, electrically attaching an anode to the substrate, immersing a cathode in said etchant solution and positioning said cathode so as not to make electrical contact with the substrate, operably connecting said anode and cathode to an ammeter;

f. directing said patterned light beam onto the immersed substrate; and

g. exposing the immersed photoactive substrate to said patterned light beam;

wherein the immersed substrate receives radiation from said patterned light beam, and said patterned light impinging on the immersed substrate enhances reactions within said bath, resulting in anisotropic etching of the immersed substrate corresponding to said mask pattern of said patterned light beam.

38. The method of claim 37, wherein generating said patterned light beam further comprises:

a. receiving mask patterns at an array of positionable micromirrors operably connected to and controllable by a computer system;

b. generating, collimating, and directing a light beam to said micromirror array;

c. positioning said micromirrors to reflect the light beam from said micromirror array according to said mask patterns provided by said computer system; and

d. collimating said patterned light beam reflected from said micromirror array.

39. The method of claim 38, further comprising varying the angular position of said micromirrors and duration of exposure of said substrate, whereby pixelation and stiction are reduced.

40. The method of claim 37, wherein generating said patterned light beam further comprises:

a. receiving mask patterns at a plasma display, having individually addressable pixels, operably connected to and controllable by said computer system,

b. activating the pixels of said plasma display to generate a patterned light beam corresponding to said mask patterns provided by said computer system; and

c. collimating said patterned light beam generated by said plasma display;

41. The method of claim 37, further comprising:

a. providing selective filtering of said patterned light beam impinging on the immersed substrate to prevent exposure of the immersed substrate during an alignment procedure;

b. allowing manual alignment of the immersed substrate under said patterned light beam by moving said outer container holding the substrate immersed in said etchant solution in three dimensions, wherein the immersed substrate is moved in coplanar first and second dimensions, and moved in a third dimension direction substantially perpendicular to said first and second coplanar dimensions, and substantially parallel to the light beam reflected from said micromirror array;

c. allowing optical monitoring of positioning of the immersed substrate under the light beam to visually verify that an image projected on the immersed substrate is properly aligned;

d. receiving alignment information corresponding to alignment of a desired mask pattern projected onto the immersed substrate;

e. generating alignment instructions based on received said alignment information;

f. providing alignment instructions, based on said alignment information, to said micromirror array to further align said mask patterns in the coplanar first and second dimensions;

g. adjusting said micromirror array according to said alignment instructions by shifting the mask pattern in at least one of the coplanar first and second dimensions;

h. disabling filtering of said patterned light beam;

i. exposing the immersed substrate; and

j. repeating steps (a-i) to create a desired pattern on the immersed substrate.

42. A method for maskless photolithography for patterning of photoreactive glass comprising:

a. receiving mask pattern information corresponding to a desired pattern to be created on said photoreactive glass substrate;

b. generating mask patterns based on received mask pattern information;

c. providing said mask patterns to a patterned light generator;

d. generating a patterned light beam;

e. directing said patterned light beam onto said photoreactive glass substrate; and

f. exposing said photoreactive glass substrate to said patterned light beam;

wherein said photoreactive glass substrate receives radiation from said patterned light beam, wherein said patterned light beam impinging on said photoreactive glass substrate creates patterns on said photoreactive glass substrate according to said mask pattern of said patterned light beam.

43. The method of claim 42, further comprising applying an acid etchant coating, reactive with said photoreactive glass substrate, to an exposed surface of said photoreactive glass substrate, wherein said photoreactive glass substrate, coated with said acid etchant, receives radiation from said patterned light beam, wherein said patterned light beam light impinging on said photoreactive glass substrate causes anisotropic etching of said photoreactive glass substrate by said acid etchant in areas corresponding to incident said patterned light beam.

44. The method of claim 42, further comprising detachably affixing a plurality of said photoreactive glass substrates around the perimeter of a circular alignment fixture, rotatably mounted on an axis, and sequentially exposing each of affixed said photoreactive glass substrates by rotating said fixture so that each of said photoreactive glass substrates is exposed to said patterned light beam.

45. The method of claim 44, further comprising providing an acid reservoir and a water reservoir, fluidically connected to an acid nozzle and a water nozzle, respectively, positioning said acid nozzle and said water nozzle above each of said photoreactive glass substrates, and sequentially applying etching acid and water rinse on each of said photoreactive glass substrates exposed to said patterned light beam.

46. The method of claim 42, wherein generating a patterned light beam further comprises:

a. receiving mask patterns at an array of positionable micromirrors, operably connected to and controllable by a computer system;

b. generating, collimating, and directing a light beam to said micromirror array;

c. positioning said micromirrors to reflect the light beam from said micromirror array according to said mask patterns provided by said computer system; and

d. collimating said patterned light beam reflected from said micromirror array;

wherein the generated light is reflected from said micromirrors in said patterned light beam corresponding to said mask patterns provided by said computer system to expose said photoreactive glass substrate and to create patterns on said photoreactive glass substrate corresponding to said mask patterns.

47. The method of claim 46, further comprising varying the angular position of said micromirrors and duration of exposure of a substrate, whereby pixelation and stiction are reduced.

48. The method of claim 42, wherein generating a patterned light beam further comprises:

a. receiving mask patterns at a plasma display, having individually addressable pixels, operably connected to and controllable by said computer system,

b. activating the pixels of said plasma display to generate a patterned light beam corresponding to said mask patterns provided by said computer system; and

c. collimating said patterned light beam generated by said plasma display;

wherein said display generates said patterned light beam corresponding to said mask patterns provided by said computer system to expose said photoreactive glass substrate to said patterned light beam and to create patterns on said photoreactive glass substrate corresponding to said mask patterns.

49. The method of claim 42, further comprising:

a. providing selective filtering of the light beam impinging on said photoreactive glass substrate to prevent exposure of said photoreactive glass substrate during an alignment procedure;

b. allowing manual alignment of said photoreactive glass substrate under the light beam by moving said photoreactive glass substrate in three dimensions, wherein said photoreactive glass substrate is moved in coplanar first and second dimensions, and moved in a third dimension direction substantially perpendicular to said first and second coplanar dimensions, and substantially parallel to the light beam reflected from said micromirror array;

c. allowing optical monitoring of positioning of said photoreactive glass substrate under the light beam to visually verify that an image projected on the substrate is properly aligned;

d. receiving alignment information corresponding to alignment of a desired mask pattern projected onto said photoreactive glass substrate;

e. generating alignment instructions based on received alignment information;

f. providing alignment instructions, based on said alignment information, to said micromirror array to further align said mask patterns in the coplanar first and second dimensions;

g. adjusting said micromirror array according to said alignment instructions by shifting the mask pattern in at least one of the coplanar first and second dimensions;

h. disabling filtering of the light beam;

i. exposing said photoreactive glass substrate; and

j. repeating steps (a-i) to create a desired pattern on said photoreactive glass substrate.

50. A method for maskless photolithography for photoselective metal deposition on a substrate comprising:

a. receiving mask pattern information corresponding to a desired pattern to be created on a said substrate;

b. generating mask patterns based on received mask pattern information;

c. providing said mask patterns to patterned light generator;

d. generating a patterned light beam;

e. coating said substrate with a light activated catalytic coating;

f. directing said patterned light beam onto said substrate; and

g. exposing said substrate to said patterned light beam;

d. immersing exposed said substrate in a deposition bath for depositing metal on said substrate corresponding to regions activated by said pattered light beam;

wherein said substrate, coated with said light activated catalyst receives radiation from said patterned light beam, wherein the light impinging on said substrate creates activated regions on said substrate corresponding to said patterned light beam, wherein metal in solution is deposited on said substrate corresponding to said activated regions.

51. The method of claim 50, further comprising rinsing said substrate after said substrate is coated with said light activated catalytic coating and before said substrate is exposed to said patterned light beam.

52. The method of claim 50, further comprising applying a coating to said substrate after said substrate receives said patterned light and before said metal is deposited on said substrate.

53. The method of claim 50, wherein immersing said substrate in a deposition bath further comprises electrically attaching an anode to said substrate, immersing a cathode in said metal plating solution and positioning said cathode so as not to make electrical contact with said substrate, connecting said anode to a positive terminal of a voltage source, and connecting said cathode to a negative terminal of said voltage source, wherein said substrate is electrically biased to receive said metal plating.

54. The method of claim 50, wherein generating said patterned light beam further comprises:

a. receiving mask patterns at an array of positionable micromirrors, operably connected to and controllable by a computer system;

b. generating, collimating, and directing a light beam to said micromirror array;

c. positioning said micromirrors to reflect the light beam from said micromirror array according to said mask patterns provided by said computer system; and

d. collimating said patterned light beam reflected from said micromirror array;

wherein the generated light is reflected from said micromirrors in said patterned light beam corresponding to said mask patterns provided by said computer system to expose a substrate and to create patterns on said substrate corresponding to said mask patterns.

55. The method of claim 54, further comprising varying the angular position of said micromirrors and duration of exposure of said substrate, whereby pixelation and stiction are reduced.

56. The method of claim 50, wherein generating a patterned light beam further comprises:

a. receiving mask patterns at a plasma display, having individually addressable pixels, operably connected to and controllable by said computer system,

b. activating the pixels of said plasma display to generate a patterned light beam corresponding to said mask patterns provided by said computer system; and

c. collimating said patterned light beam generated by said plasma display;

wherein said display generates said patterned light beam corresponding to said mask patterns provided by said computer system to expose said substrate to said patterned light beam and to create patterns on said substrate corresponding to said mask patterns.

57. The method of claim 50, further comprising:

a. providing selective filtering of the light beam impinging on the substrate to prevent exposure of the substrate during an alignment procedure;

b. allowing manual alignment of said substrate under the light beam by moving said substrate in three dimensions, wherein said substrate is moved in coplanar first and second dimensions, and moved in a third dimension direction substantially perpendicular to said first and second coplanar dimensions, and substantially parallel to the light beam reflected from said micromirror array;

c. allowing optical monitoring of positioning of the substrate under the light beam to visually verify that an image projected on the substrate is properly aligned;

d. receiving alignment information corresponding to alignment of a desired mask pattern projected onto a substrate;

e. generating alignment instructions based on received alignment information;

f. providing alignment instructions, based on said alignment information, to said micromirror array to further align said mask patterns in the coplanar first and second dimensions;

g. adjusting said micromirror array according to said alignment instructions by shifting the mask pattern in at least one of the coplanar first and second dimensions;

h. disabling filtering of the light beam;

i. exposing the substrate; and

j. repeating steps (a-i) to create a desired pattern on the substrate.