Spatial light modulators with light blocking/absorbing areas

• US 7,405,860 B2
• Filed: 03/09/2005
• Issued: 07/29/2008
• Est. Priority Date: 11/26/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Patel, Satyadev R., Huibers, Andrew G.
• Primary Examiner(s): Lester; Evelyn A.
• Application Number:
  US11/076,640
• Publication Number:
  US 20050157376A1
• Time in Patent Office: 1,238 Days
• Field of Search: 359/223, 359/224, 359290-292, 359/295, 359/298, 345/55, 345/85, 345/98, 345/108
• US Class Current: 359/290
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/0102 Calcium [Ca]
• CPC Class Codes: H01L 2924/01024 Chromium [Cr]
• CPC Class Codes: H01L 2924/01074 Tungsten [W]

Abstract

A projection system, a spatial light modulator, and a method for forming a micromirror array such as for a projection display are disclosed. The spatial light modulator can have two substrates bonded together with one of the substrates comprising a micro-mirror array. The two substrates can be bonded at the wafer level after depositing a getter material and/or solid or liquid lubricant on one or both of the wafers if desired. In one embodiment of the invention, one of the substrates is a light transmissive substrate and a light absorbing layer is provided on the light transmissive substrate to selectively block light from passing through the substrate. The light absorbing layer can form a pattern, such as a frame around an array of micro-mirrors.

Claims

1. A spatial light modulator comprising:

a semiconductor substrate having circuitry and electrodes and a dark or black material thereon;

a light transmissive substrate;

one or more intermediate substrates having an open area, wherein the semiconductor substrate, the one or more intermediate substrates and the light transmissive substrate are bonded together as a substrate assembly so as to define a cavity in the open area between the semiconductor substrate and the light transmissive substrate;

wherein the semiconductor substrate and the light transmissive substrate are bonded in an offset relationship so as to leave I/O pads exposed on the semiconductor substrate;

a group of pulse-width-modulated micromirrors for modulating a light beam incident thereon and disposed so as to be movable within said cavity; and

a dark or black mask formed as a frame around the group of micromirrors, the mask comprising chromium, titanium, tantalum, tungsten, nickel or carbon.

2. The spatial light modulator of claim 1, wherein the dark or black mask comprises carbon in the form of a polymer comprising carbon black.

3. The spatial light modulator of claim 1, wherein the dark or black mask comprises carbon in the form of carbon nitride, carbon aluminum nitride, titanium carbide, titanium carbon nitride, amorphous diamond like carbon, vitreous carbon, silicon carbide, titanium aluminum carbon nitride or tungsten carbide.

4. The spatial light modulator of claim 1, wherein the dark or black mask comprises chromium.

5. The spatial light modulator of claim 4, wherein the dark or black mask comprises black chrome.

6. The spatial light modulator of claim 1, wherein the dark or black mask comprises chromium oxide.

7. The spatial light modulator of claim 1, wherein the light transmissive substrate comprises an anti-reflective (AR) coating.

8. The spatial light modulator of claim 7, further comprising a light absorbing layer or strip along edges or sidewalls of the micromirrors.

9. The spatial light modulator of claim 1, wherein the dark or black material on the semiconductor substrate is disposed in spaces between adjacent electrodes.

10. The spatial light modulator of claim 1, wherein the dark or black material on the semiconductor substrate is disposed on the electrodes.

11. The spatial light modulator of claim 1, wherein the micromirrors are hermetically sealed within the substrate assembly from the surrounding environment.

12. The spatial light modulator of claim 11, wherein the micromirrors are heremetically sealed at a pressure lower than the surrounding environment.

13. The spatial light modulator of claim 11, wherein the micromirrors are sealed in a gas environment other than air.

14. The spatial light modulator of claim 13, wherein the micromirrors are sealed in an inert gas environment.

15. The spatial light modulator of claim 14, wherein the inert gas comprises nitrogen.

16. The spatial light modulator of claim 14, wherein the inert gas comprises helium.

17. The spatial light modulator of claim 1, wherein the semiconductor substrate comprises silicon and the light transmissive substrate comprises glass.

18. The spatial light modulator of claim 1, wherein the micromirrors are substantially square micromirror plates with torsion hinges that allow the micromirrors to move relative to the semiconductor substrate.

19. The spatial light modulator of claim 1, wherein the group of micromirrors has XGA resolution.

20. The spatial light modulator of claim 18, wherein the hinges have a thickness of 50 Å

to 2100 Å

.

21. The spatial light modulator of claim 18, wherein the hinges are formed in the same plane as the micromirror plates.

22. The spatial light modulator of claim 18, wherein the hinges are formed separated from and parallel to the micromirror plates in a different plane.

23. The spatial light modulator of claim 22, wherein the electrodes are designed to run at 0-5 V.

24. The spatial light modulator of claim 1, further comprising an SRAM or DRAM cell at each micromirror location.

25. The spatial light modulator of claim 1, wherein the substrate assembly is bonded together with an adhesive.

26. The spatial light modulator of claim 25, wherein the substrate assembly is bonded together with an epoxy.

27. The spatial light modulator of claim 1, wherein a lubricant or a getter is disposed within the cavity.

28. The spatial light modulator claim 27, wherein the lubricant and the getter are disposed within the cavity.

29. The spatial light modulator of claim 1, wherein substrates are anodically bonded together.

30. The spatial light modulator of claim 1, wherein the substrates are solder bonded together.

31. The spatial light modulator of claim 1, wherein the substrates are anodic, fusion or metal eutectic bonded together.

32. The spatial light modulator of claim 1, wherein the substrates are compression bonded together.

33. The spatial light modulator of claim 1, wherein the micromirrors have an anti-stiction layer.

34. The spatial light modulator of claim 1, wherein the cavity between the the semiconductor substrate and the light transmissive substrate is from 1 to 10 um.

35. The spatial light modulator of claim 9, wherein the dark or black material on the semiconductor substrate is disposed on the electrodes.

36. The spatial light modulator of claim 25, wherein the adhesive is a UV cured adhesive.

37. The spatial light modulator of claim 26, wherein the epoxy is a UV cured epoxy.

38. The spatial light modulator of claim 1, wherein the group of micromirrors has between 1 and 6 million micromirrors.

39. The spatial light modulator of claim 1, wherein the semiconductor substrate comprises the circuitry, the electrodes and micromirrors formed monolithically on the same semiconductor substrate.

40. The spatial light modulator of claim 27, comprising the getter in the cavity.

41. The spatial light modulator of claim 27, comprising an organic lubricant in the cavity.

42. The spatial light modulator of claim 41, wherein all of the mask, the lubricant and the getter are present on the light transmissive substrate.

43. The spatial light modulator of claim 1, wherein the semiconductor substrate is held on a lower packaging substrate.

44. The spatial light modulator of claim 1, wherein a distance between the semiconductor substrate and the light transmissive substrate is from 1 to 100 microns.

45. The spatial light modulator of claim 1, wherein a distance between the semiconductor substrate and the light transmissive substrate is from 1 to 20 microns.

46. The spatial light modulator of claim 40, wherein the getter is a moisture getter.

47. The spatial light modulator of claim 40, wherein the getter is a particle getter.

48. The spatial light modulator of claim 40, wherein the getter is a hydrogen getter.

49. The spatial light modulator of claim 40, wherein the getter is a metal oxide or zeolite getter.

50. The spatial light modulator of claim 40, wherein the getter is a combination getter.

51. The spatial light modulator of claim 1, in the absence of an additional package surrounding the substrate assembly.

52. The spatial light modulator of claim 1, wherein the dark or black mask is a multilayer structure.

53. The spatial light modulator of claim 1, wherein the light transmissive substrate is spaced apart from the semiconductor substrate at a distance of 75 microns or less.

54. The spatial light modulator of claim 1, wherein the light transmissive substrate is spaced apart from the semiconductor substrate at a distance of 50 microns or less.

55. The spatial light modulator of claim 1, wherein the dark or black mask formed around the micromirrors comprises an opaque substrate located adjacent to at least one of the one or more intermediate substrates.

56. The spatial light modulator of claim 1, wherein the dark or black mask comprises titanium.

57. The spatial light modulator of claim 1, wherein the dark or black mask comprises tantalum.

58. The spatial light modulator of claim 1, wherein the dark or black mask comprises tungsten.

59. The spatial light modulator of claim 1, wherein the dark or black mask comprises nickel.

60. The spatial light modulator of claim 1, wherein the dark or black mask comprises carbon.

61. The spatial light modulator of claim 60, wherein the dark or black mask comprises carbon and a polymer.

62. The spatial light modulator of claim 61, wherein the polymer is a polyimide.

63. A wafer assembly comprising:

a semiconductor wafer having circuitry and electrodes and a dark or black material thereon;

a light transmissive wafer;

one or more intermediate wafers having open areas, wherein the semiconductor wafer, the one or more intermediate wafers and the light transmissive wafer are bonded together with an adhesive as a wafer assembly so as to define cavities in the open areas between the semiconductor wafer and the light transmissive wafer;

groups of pulse-width-modulated micromirrors in each cavity disposed so as to be movable within each cavity;

dark or black masks formed as frames around the groups of micromirrors, the masks comprising chromium, titanium, tantalum, tungsten, nickel or carbon; and

a lubricant or a getter disposed within each cavity.

64. The wafer assembly of claim 63, further comprising horizontal and vertical scores or partial saw lines.

65. The wafer assembly of claim 64, wherein the scores or the partial saw lines are offset from each other at least in one of the horizontal or vertical directions.

66. The wafer assembly of claim 63, wherein the semiconductor wafer comprises circuitry and micromechanical structures formed monolithically on the semiconductor substrate.

67. The wafer assembly of claim 66, further comprising both the lubricant and the getter in each cavity.

68. The wafer assembly of claim 63, wherein the semiconductor wafer is held on a lower packaging substrate.

69. The wafer assembly of claim 63, wherein a distance between the semiconductor wafer and the light transmissive wafer is from 1 to 100 microns.

70. The wafer assembly of claim 63, wherein a distance between the semiconductor wafer and the light transmissive wafer is from 1 to 20 microns.

71. The wafer assembly of claim 67, wherein the getter is a moisture getter.

72. The wafer assembly of claim 67, wherein the getter is a particle getter.

73. The wafer assembly of claim 67, wherein the getter is a hydrogen getter.

74. The wafer assembly of claim 67, wherein the getter is a metal oxide or zeolite getter.

75. The wafer assembly of claim 67, wherein the getter is a combination getter.

76. The wafer assembly of claim 63 wherein the micromirrors are substantially square micromirrors, wherein torsion hinges are provided that allow the micromirrors to move relative to the semiconductor wafer, wherein the hinges have a thickness of 50 Å

to 2100 Å

, and wherein the hinges are formed separated from and parallel to the micromirrors in a different plane.

77. The wafer assembly of claim 63, wherein the wafers are bonded together hermetically.

78. The wafer assembly of claim 63, wherein the wafers are bonded together with an epoxy.

79. The wafer assembly of claim 78, wherein the epoxy is a UV cured epoxy.

80. The wafer assembly of claim 78, wherein the epoxy is a thermal cure epoxy.

81. The wafer assembly of claim 63, further comprising saw streets on the semiconductor wafer and the light transmissive wafer, wherein the saw streets are from 50 to 95% of the thickness of the wafer in which the saw streets are located.

82. The wafer assembly of claim 63, wherein the dark or black material on the semiconductor wafer comprises a material selected from chromium, titanium, tantalum, tungsten, nickel or carbon.

83. A spatial light modulator comprising:

a semiconductor substrate having circuitry and electrodes and a dark or black material thereon;

a light transmissive substrate;

a spacer layer having an open area bonded between the semiconductor substrate and the light transmissive substrate so as to hold the semiconductor substrate and the light transmissive substrate together in spaced apart relation and so as to define a cavity in the open area between the semiconductor substrate and the light transmissive substrate;

wherein the semiconductor substrate and the light transmissive substrate are bonded in an offset relationship so as to leave I/O pads exposed on the semiconductor substrate;

a group of from 6,000 to 6,000,000 pulse-width-modulated micromirrors for modulating a light beam incident thereon and disposed so as to be movable within said cavity; and

a dark or black mask formed as a frame around the group of micromirrors, the mask comprising a material selected from chromium, titanium, tantalum, tungsten, nickel or carbon.

84. A wafer assembly comprising:

a semiconductor wafer having circuitry and electrodes and a dark or black material thereon;

a light transmissive wafer;

a spacer layer having open areas and bonded between the semiconductor wafer and the light transmissive wafer so as to hold the semiconductor wafer and the light transmissive wafer together in spaced apart relation and so as to define cavities in the open areas between the semiconductor wafer and the light transmissive wafer;

wherein the semiconductor wafer and the light transmissive wafer are bonded together with an adhesive;

groups of pulse-width-modulated micromirrors in each cavity disposed so as to be movable within each cavity;

an SRAM or DRAM cell at each micromirror location; and

dark or black masks formed as frames around the groups of micromirrors, the masks comprising a material selected from chromium, titanium, tantalum, tungsten, nickel or carbon.

85. A spatial light modulator comprising:

a semiconductor substrate having circuitry and electrodes and a dark or black material thereon;

a light transmissive substrate;

one or more intermediate substrates having an open area, wherein the semiconductor substrate, the one or more intermediate substrates and the light transmissive substrate are bonded together as a substrate assembly so as to define a cavity in the open area between the semiconductor substrate and the light transmissive substrate;

wherein the semiconductor substrate and the light transmissive substrate are bonded in an offset relationship so as to leave I/O pads exposed on the semiconductor substrate;

a group of pulse-width-modulated micromirrors for modulating a light beam incident thereon and disposed so as to be movable within said cavity; and

a dark or black mask formed as a frame around the group of micromirrors, the mask comprising a polymer.

86. The spatial light modulator of claim 85, wherein the polymer is a polyimide.

87. The spatial light modulator of claim 86, wherein the polyimide comprises carbon.