Double substrate reflective spatial light modulator with self-limiting micro-mechanical elements

• US 6,947,200 B2
• Filed: 09/24/2004
• Issued: 09/20/2005
• Est. Priority Date: 06/19/1995
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Huibers, Andrew G.
• Primary Examiner(s): THOMPSON, TIMOTHY J
• Application Number:
  US10/948,871
• Publication Number:
  US 20050041277A1
• Time in Patent Office: 361 Days
• Field of Search: 359/224, 359/225, 359/290, 359/291, 359/318, 359/319, 359/223, 359/238, 359/237
• US Class Current: 359/291
• CPC Class Codes: G02B 26/08 for controlling the direction of light in light guides G02B6/35
• 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: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

A spatial light modulator includes an upper optically transmissive substrate held above a lower substrate containing addressing circuitry. One or more electrostatically deflectable elements are suspended by hinges from the upper substrate. In operation, individual mirrors are selectively deflected and serve to spatially modulate light that is incident to, and then reflected back through, the upper substrate. Motion stops may be attached to the reflective deflectable elements so that the mirror does not snap to the bottom substrate. Instead, the motion stop rests against the upper substrate thus limiting the deflection angle of the reflective deflectable elements.

Claims

1. A spatial light modulator, comprising:

a substrate that is transmissive to visible light that comprises an aperture layer;

a silicon substrate;

wherein the silicon substrate and the substrate that is transmissive to visible light are bonded together forming a gap between the substrates; and

a plurality of deflectable elements enclosed within the gap.

2. The spatial light modulator of claim 1, wherein the substrates are bonded together via melted metal.

3. The spatial light modulator of claim 1, wherein the silicon substrate comprises addressing circuitry.

4. The spatial light modulator of claim 1, wherein the silicon substrate comprises electrodes for electrostatically attracting the deflectable elements.

5. The spatial light modulator of claim 1, wherein spacers are provided to hold the substrate transmissive to visible light apart from but in proximity to the silicon substrate.

6. The spatial light modulator of claim 5, wherein the spacer are initially formed on the substrate transmissive to visible light prior to bonding the substrates together.

7. The spatial light modulator of claim 5, wherein the spacer are initially formed on the silicon substrate prior to bonding the substrates together.

8. The spatial light modulator of claim 1, wherein the deflectable elements are micromirrors each having a reflective surface.

9. The spatial light modulator of claim 8, wherein the reflective surface comprises aluminum.

10. The spatial light modulator of claim 8, wherein a plurality of dielectric layers are provided on the reflective surface of each micromirror.

11. The spatial light modulator of claim 10, wherein the plurality of dielectric layers have thicknesses and optical indices to increase the reflectivity of the reflective layer.

12. The spatial light modulator of claim 11, wherein the plurality of dielectric layers comprises silicon dioxide or silicon nitride.

13. The spatial light modulator of claim 8, wherein a layer of silicon dioxide is provided on the reflective surface.

14. The spatial light modulator of claim 8, wherein a layer of silicon nitride is provided on the reflective surface.

15. The spatial light modulator of claim 4, wherein other circuit components are provided on the silicon substrate, and wherein the electrodes are physically located higher than other circuit components.

16. The spatial light modulator of claim 1, wherein the deflectable elements are micromirrors, with the distance separating neighboring micromirrors being 0.5 microns or less.

17. The spatial light modulator of claim 8, wherein the micromirrors are electrically connected together.

18. The spatial light modulator of claim 17, wherein the micromirrors are at the same potential.

19. The spatial light modulator of claim 17, wherein the micromirrors are connected to ground.

20. The spatial light modulator of claim 18, wherein at a point during micromirror addressing, the micromirrors are maintained at a negative potential.

21. The spatial light modulator of claim 18, wherein the voltage is capable of being altered.

22. The spatial light modulator of claim 1, wherein the aperture layer is made of an opaque material.

23. The spatial light modulator of claim 1, wherein the aperture layer eliminates unwanted light scattering.

24. The spatial light modulator of claim 1, wherein the deflectable elements each comprise a reflective plate and a hinge.

25. The spatial light modulator of claim 24, wherein the hinge is a torsion type hinge that crosses the plate and attaches at a point on the plate.

26. The spatial light modulator of claim 24, further comprising a gap between the reflective plate and hinge.

27. The spatial light modulator of claim 24, wherein during operation one part of the micromirror plate moves toward the silicon substrate while another part moves away from the silicon substrate.

28. The spatial light modulator of claim 1, wherein the substrate that is transmissive to visible light comprises a transparent electrode thereon.

29. The spatial light modulator of claim 28, wherein the transparent electrode attracts the deflectable element back from the silicon substrate.

113. The spatial light modulator of claim 14, wherein the mirror plate comprise a first and second portions such that during the rotation of the mirror plate, the second portion moves towards the glass substrate and the first portion moves away from the glass substrate;

and wherein the hinge and the mirror plate are positioned in different planes.

30. A spatial light modulator, comprising:

a substrate that is transmissive to visible light that further comprises an aperture layer for eliminating unwanted light scattering;

a silicon substrate having electrodes and circuitry thereon;

wherein the silicon substrate and the substrate that is transmissive to visible light are bonded together forming a gap therebetween; and

a plurality of micromirrors enclosed within the gap.

31. The spatial light modulator of claim 30, wherein the circuitry comprises DRAM cells.

32. The spatial light modulator of claim 30, wherein the distance between the substrates is from 1 to 5 microns.

33. The spatial light modulator of claim 30, wherein the substrate that is transmissive to visible light further comprises a transparent electrode for electrostatically attracting the micromirrors.

34. The spatial light modulator of claim 30, wherein the substrate that is transmissive to visible light is glass.

35. The spatial light modulator of claim 30, wherein the substrate that is transmissive to visible light is quartz.

36. The spatial light modulator of claim 30 further comprising:

a first pattern on the substrate that is transmissive to visible light;

a second pattern on the silicon substrate; and

wherein the first and second patterns are aligned together when the substrates are bonded together.

37. The spatial light modulator of claim 30, wherein spacers are provided proximate to the micromirrors to maintain a gap between the substrates.

38. The spatial light modulator of claim 30, wherein the spacer is a patterned material formed on the substrate transmissive to visible light.

39. The spatial light modulator of claim 30, wherein a single addressing electrode per micromirror is provided on the silicon substrate.

40. The spatial light modulator of claim 39, wherein the micromirrors are electrically connected to each other and held at the same potential.

41. The spatial light modulator of claim 30, wherein the substrates are aligned together such that each micromirror is aligned with one electrode on the silicon substrate.

42. The spatial light modulator of claim 30, wherein the circuitry comprises SRAM addressing circuitry.

43. The spatial light modulator of claim 30, wherein the circuitry is passive addressing circuitry.

44. The spatial light modulator of claim 30, where the micromirrors operate in binary mode.

45. The spatial light modulator of claim 44, wherein the micromirrors comprise a reflective metal layer and a layer of silicon dioxide or silicon nitride.

46. The spatial light modulator of claim 45, wherein the micromirrors comprise hinges and mirror plates formed in separate planes and having a gap therebetween.

47. The spatial light modulator of claim 43, wherein each mirror plate is attached to a hinge that crosses the mirror plate and attaches at a single point on the mirror plate.

48. The spatial light modulator of claim 47, wherein the hinge is a torsion hinge.

49. The spatial light modulator of claim 47, wherein the mirror plate comprise a first and second portions such that during the rotation of the mirror plate, the second portion moves towards the glass substrate and the first portion moves away from the glass substrate;

and wherein the hinge and the mirror plate are positioned in different planes.

50. A spatial light modulator, comprising:

a first substrate having an array of electrodes and circuitry;

a second substrate where a plurality of micromirrors are fabricated on the second substrate, wherein the second substrate comprises an aperture layer for eliminating unwanted light scattering; and

wherein the first and second substrates are bonded together with, at each pixel location, a single electrode on the first substrate aligned proximate to a single micromirror on the second substrate.

51. A spatial light modulator, comprising:

a first substrate; and

a second substrate, wherein the first and the second substrates are bonded together with a spacer therebetween so as to form a gap between the substrates; and

a plurality of micromirrors positioned within the gap, each micromirror further comprising;

a mirror plate, further comprising;

a first and second portions, wherein the second portion moves away from the first substrate when the first portion moves towards the first substrate;

a hinge that is located in a plane other than a plane in which the mirror plate is located;

wherein the mirror plate is attached to the hinge such that the mirror plate is operable to rotate.

52. The spatial light modulator of claim 51, wherein the distance between the substrates is from 1 to 5 microns.

53. The spatial light modulator of claim 51, wherein one of the first and second substrates is a silicon substrate.

54. The spatial light modulator of claim 53, wherein the silicon substrate comprises a plurality of addressing electrodes, one per mirror plate, for electrostatically attracting the mirror plates during operation.

55. The spatial light modulator of claim 51, wherein the substrates are bonded together via melted metal.

56. The spatial light modulator of claim 51, wherein spacers are provided to hold the substrate transmissive to visible light apart from but in proximity to the silicon substrate.

57. The spatial light modulator of claim 51, wherein each mirror plate comprises a reflective surface of aluminum.

58. The spatial light modulator of claim 53, wherein the silicon substrate comprises electrodes and other circuit components, wherein the electrodes are physically located higher than other circuit components.

59. The spatial light modulator of claim 51, wherein the deflectable elements are micromirrors, with the distance separating neighboring micromirrors being 0.5 microns or less.

60. The spatial light modulator of claim 51, wherein the micromirrors are electrically connected together.

61. The spatial light modulator of claim 51,wherein the micromirrors are at the same potential.

62. The spatial light modulator of claim 51, wherein the micromirrors are connected to ground.

63. The spatial light modulator of claim 60, wherein the hinge is a torsion type hinge that crosses the plate and attaches at a point on the plate.

64. The spatial light modulator of claim 63, wherein a gap is defined between the reflective plate and hinge.

65. The spatial light modulator of claim 64, wherein during operation one part of the micromirror plate moves toward the silicon substrate while another part moves away from the silicon substrate.

66. A spatial light modulator, comprising:

a substrate that is transmissive to visible light;

a silicon substrate;

wherein the silicon substrate and the substrate that is transmissive to visible light are bonded together forming a gap between the substrates;

a plurality of deflectable elements enclosed within the gap;

wherein the silicon substrate comprises a plurality of electrodes for electrostatically attracting the deflectable elements; and

wherein the silicon substrate further comprises a plurality of other circuit components, and wherein the electrodes are physically located higher than the other circuit components.

67. The spatial light modulator of claim 66, wherein the substrates are bonded together via melted metal.

68. The spatial light modulator of claim 66, wherein the silicon substrate comprises addressing circuitry.

69. The spatial light modulator of claim 66, wherein the silicon substrate comprises electrodes for electrostatically attracting the deflectable elements.

70. The spatial light modulator of claim 66, wherein spacers are provided to hold the substrate transmissive to visible light apart from but in proximity to the silicon substrate.

71. The spatial light modulator of claim 70, wherein the spacer are initially formed on the substrate transmissive to visible light prior to bonding the substrates together.

72. The spatial light modulator of claim 70, wherein the spacer are initially formed on the silicon substrate prior to bonding the substrates together.

73. The spatial light modulator of claim 66, wherein the deflectable elements are micromirrors each having a reflective surface.

74. The spatial light modulator of claim 73, wherein the reflective surface comprises aluminum.

75. The spatial light modulator of claim 73, wherein a plurality of dielectric layers are provided on the reflective surface of each micromirror.

76. The spatial light modulator of claim 75, wherein the plurality of dielectric layers have thicknesses and optical indices to increase the reflectivity of the reflective layer.

77. The spatial light modulator of claim 76, wherein the plurality of dielectric layers comprises silicon dioxide or silicon nitride.

78. The spatial light modulator of claim 73, wherein a layer of silicon dioxide is provided on the reflective surface.

79. The spatial light modulator of claim 73, wherein a layer of silicon nitride is provided on the reflective surface.

80. The spatial light modulator of claim 66, wherein the deflectable elements are micromirrors, with the distance separating neighboring micromirrors being 0.5 microns or less.

81. The spatial light modulator of claim 73, wherein the micromirrors are electrically connected together.

82. The spatial light modulator of claim 81, wherein the micromirrors are at the same potential.

83. The spatial light modulator of claim 81, wherein the micromirrors are connected to ground.

84. The spatial light modulator of claim 83, wherein at a point during micromirror addressing, the micromirrors are maintained at a negative potential.

85. The spatial light modulator of claim 83, wherein the voltage is capable of being altered.

86. The spatial light modulator of claim 66, wherein the light transmissive substrate further comprises am aperture layer.

87. The spatial light modulator of claim 86, wherein the aperture layer is made of an opaque material.

88. The spatial light modulator of claim 86, wherein the aperture layer eliminates unwanted light scattering.

89. The spatial light modulator of claim 66, wherein the deflectable elements each comprise a reflective plate and a hinge.

90. The spatial light modulator of claim 89, wherein the hinge is a torsion type hinge that crosses the plate and attaches at a point on the plate.

91. The spatial light modulator of claim 90, further comprising a gap between the reflective plate and hinge.

92. The spatial light modulator of claim 90, wherein during operation one part of the micromirror plate moves toward the silicon substrate while another part moves away from the silicon substrate.

93. The spatial light modulator of claim 66, wherein the substrate that is transmissive to visible light comprises a transparent electrode thereon.

94. The spatial light modulator of claim 93, wherein the transparent electrode attracts the deflectable element back from the silicon substrate.

95. A spatial light modulator, comprising:

a substrate that is transmissive to visible light;

a silicon substrate having electrodes and circuitry thereon;

wherein the silicon substrate and the substrate that is transmissive to visible light are bonded together forming a gap therebetween; and

a plurality of micromirrors enclosed within the gap, wherein the micromirrors operate in binary mode;

wherein the micromirrors comprise a reflective metal layer; and

wherein the micromirrors comprise hinges and mirror plates formed in separate planes and having a gap therebetween.

96. The spatial light modulator of claim 95, wherein the circuitry comprises DRAM cells.

97. The spatial light modulator of claim 95, wherein the distance between the substrates is from 1 to 5 microns.

98. The spatial light modulator of claim 95, wherein the substrate that is transmissive to visible light further comprises a transparent electrode for electrostatically attracting the micromirrors.

99. The spatial light modulator of claim 95, wherein the substrate that is transmissive to visible light further comprises an aperture layer for eliminating unwanted light scattering.

100. The spatial light modulator of claim 95, wherein the substrate that is transmissive to visible light is glass.

101. The spatial light modulator of claim 95, wherein the substrate that is transmissive to visible light is quartz.

102. The spatial light modulator of claim 95, further comprising:

a first pattern on the substrate that is transmissive to visible light;

a second pattern on the silicon substrate; and

wherein the first and second patterns are aligned together when the substrates are bonded together.

103. The spatial light modulator of claim 95, wherein spacers are provided proximate to the micromirrors to maintain a gap between the substrates.

104. The spatial light modulator of claim 95, wherein the spacer is a patterned material formed on the substrate transmissive to visible light.

105. The spatial light modulator of claim 95, wherein a single addressing electrode per micromirror is provided on the silicon substrate.

106. The spatial light modulator of claim 105, wherein the micromirrors are electrically connected to each other and held at the same potential.

107. The spatial light modulator of claim 95, wherein the substrates are aligned together such that each micromirror is aligned with one electrode on the silicon substrate.

108. The spatial light modulator of claim 95, wherein the circuitry comprises SRAM addressing circuitry.

109. The spatial light modulator of claim 95, wherein the circuitry is passive addressing circuitry.

110. The spatial light modulator of claim 109, wherein the micromirrors further comprise a layer of silicon dioxide or silicon nitride.

111. The spatial light modulator of claim 109, wherein each mirror plate is attached to a hinge that crosses the mirror plate and attaches at a single point on the mirror plate.

112. The spatial light modulator of claim 111, wherein the hinge is a torsion hinge.

114. A spatial light modulator, comprising:

a substrate that is transmissive to visible light;

a silicon substrate having electrodes and circuitry thereon;

wherein the silicon substrate and the substrate that is transmissive to visible light are bonded together forming a gap therebetween;

a plurality of micromirrors enclosed within the gap; and

a single addressing electrode per micromirror is provided on the silicon substrate.