Spatial light modulators with light blocking/absorbing areas

• US 6,906,847 B2
• Filed: 11/26/2002
• Issued: 06/14/2005
• Est. Priority Date: 12/07/2000
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Patel, Satyadev R., Huibers, Andrew G.
• Primary Examiner(s): Lester, Evelyn A.
• Application Number:
  US10/305,536
• Publication Number:
  US 20040100677A1
• Time in Patent Office: 931 Days
• Field of Search: 359223-224, 359290-292, 359/295, 359/298
• US Class Current: 359/291
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 7/0077 Other packages not provided for in groups B81B7/0035 - B81B7/0074
• CPC Class Codes: B81C 1/00896 Temporary protection during separation into individual elements
• CPC Class Codes: B81C 1/00904 Multistep processes for the separation of wafers into individual elements not provided for in groups B81C1/00873 - B81C1/00896
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• 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 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01018 Argon [Ar]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/0102 Calcium [Ca]
• CPC Class Codes: H01L 2924/01023 Vanadium [V]
• CPC Class Codes: H01L 2924/01024 Chromium [Cr]
• CPC Class Codes: H01L 2924/01027 Cobalt [Co]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01039 Yttrium [Y]
• CPC Class Codes: H01L 2924/01041 : Niobium [Nb]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/01054 : Xenon [Xe]
• CPC Class Codes: H01L 2924/01058 : Cerium [Ce]
• CPC Class Codes: H01L 2924/01072 : Hafnium [Hf]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01077 : Iridium [Ir]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/04953 : TaN
• CPC Class Codes: H01L 2924/10329 : Gallium arsenide [GaAs]
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/12044 : OLED
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/1433 : Application-specific integrated circuit [ASIC]
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/19042 : being an inductor
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding

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 method for making a spatial light modulator, comprising:

providing a first substrate that is transmissive to visible light;

providing a second substrate having an array of circuitry and electrodes thereon;

depositing a light absorbing layer on the first substrate to selectively block the passage of light through the first substrate, wherein the light absorbing layer is black or dark in color;

forming an array of deflectable reflective elements on the first or second substrate; and

positioning the first and second substrates proximate to each other to form a substrate assembly, further comprising;

bonding the first and second substrates together to form the substrate assembly; and

singulating the substrate assembly into a set of assembly dies, each of which comprises a plurality of deflectable reflective elements.

2. The method of claim 1, wherein the light absorbing layer is formed as a frame such that after singulation, each assembly die is surrounded by the frame.

3. The method of claim 1, wherein the deflectable reflective elements correspond to pixels in a direct-view or projection display.

4. The method of claim 1, wherein the light absorbing layer is formed as a rectangular frame on the first substrate surrounding the array of deflectable reflective elements.

5. The method of claim 4, wherein light absorbing material is deposited on the first substrate to further form areas that decrease the amount of light that enters gaps between the deflectable elements.

6. The method of claim 1, wherein the light absorbing layer is formed as strips, frames or a grid on the first substrate fully or partially surrounding each deflectable element, when viewed from above, so as to decrease light that enters gaps between adjacent deflectable elements.

7. The method of claim 4, wherein the light absorbing layer is deposited prior to fanning the array of deflectable reflective elements.

8. The method of claim 4, wherein the light absorbing layer is deposited after forming the array of deflectable reflective elements.

9. The method of claim 1, wherein the first and second substrates are bonded together with an adhesive.

10. The method of claim 1, wherein the light absorbing layer absorbs at least 50% of the light in areas where the light absorbing layer is disposed.

11. The method of claim 10, wherein the light absorbing layer absorbs at least 75% of the light in areas where the light absorbing layer is disposed.

12. The method of claim 11, wherein the light absorbing layer absorbs at least 85% of the light in areas where the light absorbing layer is disposed.

13. The method of claim 1, wherein the light absorbing layer is a light absorbing matrix.

14. The method of claim 13, wherein the number of reflective elements in each die is from 6,000 to about 6 million.

15. The method of claim 1, wherein the first substrate is an optically transmissive substrate or a substrate having one or more layers that when removed result in an optically transmissive substrate in an area other than in an area of the light absorbing layer.

16. The method of claim 15, wherein the first substrate is glass, borosilicate, tempered glass, quartz or sapphire.

17. The method of claim 1, wherein the second substrate is a dielectric or semiconductor substrate.

18. The method of claim 17, wherein the second substrate comprises GaAs or silicon.

19. The method of claim 1, wherein the bonding comprises applying an adhesive and spacers, the spacers having a size of from 1 to 100 microns.

20. The method of claim 19, wherein the spacers have a size of from 1 to 20 microns.

21. The method of claim 1, wherein the plurality of deflectable elements are reflective mirror elements and are formed on the second substrate which is a light transmissive substrate when in use except in areas of the light absorbing layer.

22. The method of claim 1, wherein the circuitry and plurality of electrodes are funned prior to forming the plurality of deflectable elements, wherein the plurality of deflectable elements is formed above the plurality of electrodes on the second substrate.

23. The method of claim 22, wherein a plurality of light absorbing masks are formed on the first substrate.

24. The method of claim 23, wherein when the substrate assembly is singulated into substrate assembly dies, a light absorbing mask is disposed on a first substrate portion within each substrate assembly die.

25. The method of claim 1, wherein the plurality of deflectable elements is formed on the first substrate.

26. The method of claim 25, wherein when the first and second substrates are aligned and bonded together, the deflectable elements on the first substrate are each disposed proximate to a corresponding electrode on the second substrate.

27. The method of claim 1, wherein the deflectable elements are micromirrors having jagged or zig-zag edges.

28. The method of claim 1, further comprising applying a stiction reducing agent to one or both substrates before or after bonding the two substrates together, but before singulating the substrate assembly into dies.

29. The method of claim 28, wherein the stiction reducing agent is a silane applied to the deflectable elements.

30. The method of claim 28, wherein the stiction reducing agent is a chlorosilane.

31. The method of claim 1, further comprising the singulated die into a projection system that comprises a light source, a color sequencer and projection optics.

32. The method of claim 1, wherein the light absorbing layer is provided as a grid or matrix on the light transmissive substrate.

33. The method of claim 1, wherein the light absorbing layer is provided as strips or bands on the light transmissive substrate.

34. The method of claim 1, wherein the light absorbing layer is black nickel or black chrome.

35. The method of claim 1, wherein the light absorbing layer is a black or dark colored metal or metal alloy.

36. The method of claim 1, wherein the light absorbing layer is a carbon containing polymer.

37. The method of claim 1, wherein the light absorbing layer is deposited by sputtering.

38. The method of claim 1, wherein the light absorbing layer is a carbon containing film.

39. The method of claim 1, wherein the light absorbing layer comprises a carbon compound.

40. The method of claim 1, wherein the light absorbing layer is a multilayer laminate.

41. The method of claim 1, wherein the light transmissive substrate comprises an AR coating on a surface opposite to the surface having the light absorbing layer.

42. The method of claim 1, wherein the light absorbing layer is alight absorbing frame surrounding each micromirror.

43. The method of claim 1, wherein the light absorbing layer comprises a plurality of light blocking strips, each of which are proximate to a gap between adjacent micromirrors.

44. The method of claim 1, wherein the light absorbing layer is a set of light absorbing frames, each of which surrounding a micromirror.

45. The method of claim 44, wherein the light absorbing frame surrounding each micromirror is on the same side of the first substrate as the micromirrors.

46. The method of claim 45, wherein the light absorbing frame is on a side of the first substrate opposite to the side on which the micromirrors are formed.

47. The method of claim 1, wherein the first substrate is bonded to the second substrate at a distance of 75 microns or less from the second substrate.

48. The method of claim 47, wherein the first substrate is bonded to the second substrate at a distance of less than 10 microns from the second substrate.

49. A projection system, comprising:

a light source;

the spatial light modulator of claim 1 for reflecting a beam of light from the light source; and

projection optics for projecting light reflected off of the spatial light modulator.

50. A spatial tight modulator, comprising:

a first substrate that is transmissive to visible light;

a second substrate having an array of circuitry and electrodes thereon;

a light absorbing layer on the first substrate disposed to selectively block the passage of light through the first substrate, wherein the light blocking layer is black or dark in color; and

an array of deflectable reflective elements on the first or second substrate;

wherein the first and second substrates are positioned proximate to each other as a substrate assembly.

51. The spatial light modulator of claim 50, wherein the reflective elements correspond to pixels in a direct-view or projection display.

52. The spatial light modulator of claim 50, wherein the light absorbing layer is formed as a rectangular frame on the first substrate surrounding the any of deflectable reflective elements as viewed from above.

53. The spatial light modulator of claim 52, wherein a further light absorbing area is formed as strips, frames or a grid for blocking light between adjacent deflectable elements.

54. The spatial light modulator of claim 50, wherein the first and second substrates are bonded together.

55. The spatial light modulator of claim 50, wherein the light absorbing layer absorbs at least 50% of the light in areas where the light absorbing layer is disposed.

56. The spatial light modulator of claim 55, wherein the light absorbing layer absorbs at least 75% of the light in areas where the light absorbing layer is disposed.

57. The spatial light modulator of claim 56, wherein the light absorbing layer absorbs at least 85% of the light in areas where the light absorbing layer is disposed.

58. The spatial light modulator of claim 50, wherein the light absorbing layer is a light absorbing matrix.

59. The spatial light modulator of claim 58, wherein the number of reflective elements in a die area is from 6,000 to about 6 million.

60. The spatial light modulator of claim 50, wherein the first substrate is an optically transmissive substrate in areas other than in the area of the light absorbing layer.

61. The spatial light modulator of claim 60, wherein the first substrate is glass, borosilicate, tempered glass, quartz or sapphire.

62. The spatial light modulator of claim 50, wherein the second substrate is a glass or quartz substrate.

63. The spatial light modulator of claim 50, wherein the second substrate is a dielectric or semiconductor substrate.

64. The spatial light modulator of claim 63, wherein the second substrate comprises GaAs or silicon.

65. The spatial light modulator of claim 50, wherein the first and second substrates are bonded together with an adhesive.

66. The spatial light modulator of claim 50, wherein the second substrate is a glass substrate.

67. The spatial light modulator of claim 50, wherein the plurality of deflectable elements are reflective mirror elements and are held on the second substrate which is a light transmissive substrate.

68. The spatial light modulator of claim 50, wherein the plurality of deflectable elements are formed on the second substrate.

69. The spatial light modulator of claim 68, wherein the circuitry and plurality of electrodes are disposed on the second substrate, wherein the plurality of deflectable elements are formed spaced above the plurality of electrodes on the second substrate.

70. The spatial light modulator of claim 69, wherein a plurality of light absorbing masks arc formed on the first substrate.

71. The spatial light modulator of claim 70, wherein the substrate assembly is a substrate assembly die having a light absorbing mask disposed on a first substrate portion within the substrate assembly die.

72. The spatial light modulator of claim 50, wherein the plurality of deflectable elements is formed on the first substrate.

73. The spatial light modulator of claim 50, wherein the deflectable elements are micromirrors having jagged or zig-zag edges.

74. The spatial light modulator of claim 50, further comprising a stiction reducing agent on one or both substrates.

75. The spatial light modulator of claim 50, further comprising a getter on one or both substrates.

76. The spatial light modulator of claim 75, wherein the getter is a molecular, hydrogen and/or particle getter.

77. The spatial light modulator of claim 75, wherein the getter is a particulate and moisture getter.

78. The spatial light modulator of claim 75, wherein the getter is capable of absorbing moisture.

79. The spatial light modulator of claim 50, wherein the light absorbing layer is provided as strips or bands on the light transmissive substrate.

80. The spatial light modulator of claim 50, wherein the light absorbing layer is black nickel or black chrome.

81. The spatial light modulator of claim 50, wherein the light absorbing layer is a black or dark colored metal or metal alloy.

82. The spatial light modulator of claim 50, wherein the light absorbing layer is a carbon containing polymer.

83. The spatial light modulator of claim 50, wherein the light absorbing layer is deposited by sputtering.

84. The spatial light modulator of claim 50, wherein the light absorbing layer is a carbon containing film.

85. The spatial light modulator of claim 50, wherein the light absorbing layer comprises a carbon compound.

86. The spatial light modulator of claim 50, wherein the light absorbing layer is a multilayer laminate.

87. The spatial light modulator of claim 50, wherein the light transmissive substrate comprises an AR coating on a surface opposite to the surface having the light absorbing layer.

88. The spatial light modulator of claim 50, wherein the light absorbing layer is a light absorbing frame around each die area.

89. The spatial light modulator of claim 50, wherein tho light absorbing layer is a light absorbing frame surrounding each micromirror.

90. The spatial light modulator of claim 50, wherein the light absorbing layer comprises light absorbing strips proximate to gaps between adjacent micromirrors.

91. The spatial light modulator of claim 88, wherein the light absorbing layer is a light absorbing frame surrounding each micromirror.

92. The spatial light modulator of claim 91, wherein the light absorbing frame surrounding each micromirror is on the same side of the first substrate as the micromirrors.

93. The spatial light modulator of claim 92, wherein the light absorbing frame surrounding each die is on a side of the first substrate opposite to the side on which the micromirrors are formed.

94. The spatial light modulator of claim 50, wherein the first substrate is bonded to the second substrate at a distance of 75 microns or less from the second substrate.

95. The spatial light modulator of claim 94, wherein the first substrate is bonded to the second substrate at a distance of less than 10 microns from the second substrate.

96. The spatial light modulator of claim 95, wherein the first substrate is bonded to the second substrate at a distance of from 1 to 10 microns from the second substrate.

97. A method for making a spatial light modulator, comprising:

providing a first substrate and a second substrate;

forming an array of circuitry and electrodes on the second substrate;

forming a plurality of strips or frame areas on the first substrate to absorb at least 50% of the light incident on the strips or frame areas;

forming an array of deflectable reflective elements on the first or second substrate; and

bonding the first and second substrates together to form a substrate assembly.

98. A spatial light modulator, comprising:

a first substrate arid a second substrate;

an array of circuitry and electrodes on the second substrate;

an opaque layer that forms a pattern on the first substrate in order to absorb at least 50% of the light that is incident on the opaque layer; and

an array of deflectable reflective elements on the first or second substrate;

wherein the first and second substrates are positioned proximate to each other as a substrate assembly.

99. A method for making a spatial light modulator, comprising:

providing a first substrate that is transmissive to visible light;

providing a second substrate having an array of circuitry and electrodes thereon;

depositing a light absorbing layer on the first substrate to selectively block the passage of light through the first substrate, wherein the light absorbing layer is black or dark in color;

forming an array of deflectable reflective elements; and

positioning the first and second substrates proximate to each other to form a substrate assembly such that the array of deflectable reflective elements are positioned between the first and second substrates, further comprising;

bonding the first and second substrates together to form the substrate assembly; and

singulating the substrate assembly into a set of assembly dies, each of which comprises a plurality of deflectable reflective elements.