Spatial light modulators with light absorbing areas

US 20040100594A1
Filed: 11/26/2002
Published: 05/27/2004
Est. Priority Date: 11/26/2002
Status: Active Grant

First Claim

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

forming an array of circuitry and electrodes on a first substrate;

forming a light absorbing layer on the first substrate to reduce reflections from the circuitry and/or electrodes on the substrate;

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

wherein the light absorbing layer is formed of a material that absorbs at least 50% of the light incident thereon and has a resistivity of from 2.5e12 ohm-cm (should it be “

ohm per cm squared or per cm”

?) to 1e15 ohm-cm.

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Abstract

A projection system, a spatial light modulator, and a method for forming micromirrors are disclosed. A substrate comprises circuitry and electrodes for electrostatically deflecting micromirror elements that are disposed within an array of such elements forming the spatial light modulator. In one embodiment, the substrate is a silicon substrate having circuitry and electrodes thereon for electrostatically actuating adjacent micromirror elements, and the substrate is fully or selectively covered with a light absorbing material.

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140 Claims

1. A method for making a spatial light modulator, comprising:
- forming an array of circuitry and electrodes on a first substrate;
  
  forming a light absorbing layer on the first substrate to reduce reflections from the circuitry and/or electrodes on the substrate;
  
  forming an array of deflectable reflective elements on the first substrate or on a second substrate; and
  
  wherein the light absorbing layer is formed of a material that absorbs at least 50% of the light incident thereon and has a resistivity of from 2.5e12 ohm-cm (should it be “
  
  ohm per cm squared or per cm”
  
  ?) to 1e15 ohm-cm.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 139, 140)
- - 2. The method of claim 1, further comprising:
    - positioning the first and second substrates proximate to each other.
  - 3. The method of claim 2, wherein the array of deflectable elements is formed on the second substrate, and wherein the positioning of the first and second substrates proximate to each other comprises bonding the first and second substrates together to form the substrate assembly followed by singulating the substrate assembly into a set of assembly dies, each of which comprises a plurality of deflectable reflective elements.
  - 4. The method of claim 3, wherein the deflectable reflective elements correspond to a plurality of pixels in a direct-view or projection display.
  - 5. The method of claim 1, wherein the light absorbing layer is formed as a grid for decreasing the amount of light that enters gaps between the deflectable elements.
  - 6. The method of claim 5, wherein an additional light absorbing area is formed as a rectangular frame on the second substrate surrounding the array of deflectable reflective elements.
  - 7. The method of claim 1, wherein the light absorbing layer is formed as a grid on the second substrate for decreasing light that enters gaps between adjacent deflectable elements, and as a block of rectangular frames on the second substrate, each frame surrounding an array of deflectable reflective elements.
  - 8. The method of claim 5, further comprising:
    - depositing the light absorbing layer prior to forming the array of deflectable reflective elements.
  - 9. The method of claim 6, further comprising:
    - depositing the light absorbing layer after forming the array of deflectable reflective elements.
  - 10. The method of claim 1, wherein the light absorbing layer is black in color.
  - 11. The method of claim 1, wherein the light absorbing layer absorbs at least 50% of the light incident thereon.
  - 12. The method of claim 11, wherein the light absorbing layer absorbs at least 75% of the light incident thereon.
  - 13. The method of claim 12, wherein the light absorbing layer absorbs at least 85% of the light incident thereon.
  - 14. The method of claim 3, further comprising:
    - forming a light absorbing matrix layer on the second substrate so as to decrease the amount of light entering gaps between adjacent deflectable elements.
  - 15. The method of claim 3, wherein the number of reflective elements in each die is from 6,000 to about 6 million.
  - 16. The method of claim 1, wherein the second substrate is an optically transmissive substrate or a substrate having one or more layers that when removed result in an optically transmissive substrate in areas other than in the area of the light absorbing layer.
  - 17. The method of claim 16, wherein the second substrate is glass, borosilicate, tempered glass, quartz or sapphire.
  - 18. The method of claim 1, wherein the first substrate is a dielectric or semiconductor substrate.
  - 19. The method of claim 18, wherein the first substrate is a GaAs or silicon substrate.
  - 20. The method of claim 1, wherein the second and first substrates are bonded together with an adhesive.
  - 21. The method of claim 20, wherein the adhesive is an epoxy.
  - 22. The method of claim 1, wherein the first substrate is a glass or quartz substrate.
  - 23. The method of claim 3, wherein the bonding of the substrates comprises the dispensing of a UV or thermal cure epoxy.
  - 24. The method of claim 2, wherein the aligning comprises aligning each deflectable element on the second substrate with at least one electrode on the first substrate.
  - 25. The method of claim 3, wherein the singulation of the substrate assembly comprises sawing partially through each substrate followed by breaking along the sawed lines.
  - 26. The method of claim 3, wherein the bonding comprises applying a sealant near the perimeter of each array on the substrate.
  - 27. The method of claim 1, wherein the plurality of deflectable elements are reflective mirror elements and are formed on the first substrate which is a light transmissive substrate.
  - 28. The method of claim 1, wherein the plurality of deflectable elements are formed on the first substrate.
  - 29. The method of claim 1, wherein the circuitry and plurality of electrodes are formed prior to forming the plurality of deflectable elements, wherein the plurality of deflectable elements are formed above the plurality of electrodes on the first substrate.
  - 30. The method of claim 29, wherein the deflectable elements are held by at least a post connected to the first substrate so that each deflectable element is pivotably held above one or more electrodes.
  - 31. The method of claim 3, wherein when the substrate assembly is singulated into substrate assembly dies, a light absorbing mask is disposed on a portion within each substrate assembly die on the second substrate.
  - 32. The method of claim 1, wherein the plurality of deflectable elements are formed on the second substrate.
  - 33. The method of claim 32, wherein when the second and first substrates are aligned and bonded together, the deflectable elements on the second substrate are each disposed proximate to a corresponding electrode on the first substrate.
  - 34. The method of claim 1, wherein the deflectable elements are micromirrors having jagged or zig-zag edges.
  - 35. The method of claim 1, wherein the light absorbing layer is black nickel or black chrome.
  - 36. The method of claim 1, wherein the light absorbing layer is a black or dark colored metal or metal alloy.
  - 37. The method of claim 1, wherein the light absorbing layer is a carbon containing polymer.
  - 38. The method of claim 1, wherein the light absorbing layer is deposited by sputtering.
  - 39. The method of claim 1, wherein the light absorbing layer is a carbon containing film.
  - 40. The method of claim 1, wherein the light absorbing layer comprises a carbon compound.
  - 41. The method of claim 1, wherein the light blocking layer is a multilayer film.
  - 42. The method of claim 1, wherein the light transmissive substrate comprises an anti-reflection coating on a surface opposite to the surface having the light blocking layer.
  - 43. The method of claim 1, wherein the light blocking layer is a light blocking frame around each die area.
  - 44. The method of claim 1, wherein the light blocking layer is a light blocking frame surrounding each micromirror.
  - 45. The method of claim 1, wherein the light blocking layer comprises a plurality of light blocking strips, each of which proximate to a gap between adjacent micromirrors.
  - 46. The method of claim 3, wherein the second substrate is bonded to the first substrate at a distance of less than 10 microns from the first substrate.
  - 139. A spatial light modulator formed by the method of any of claims 1, 87, 88, 104, 199, 126, 127 or 134.
  - 140. A projection system, comprising:
    - a light source;
      
      a spatial light modulator for reflecting a beam of light from the light source; and
      
      a plurality of projection optics for projecting light reflected off of the spatial light modulator onto a target;
      
      wherein the spatial light modulator is formed by a method of any of claims 1, 87, 88, 119, 126, 127 or 134.

47. A spatial light modulator, comprising:
- an array of circuitry and electrodes on a first substrate;
  
  a light absorbing layer on the first substrate to reduce reflections from the circuitry and/or electrodes on the first substrate;
  
  an array of micromirrors on the first substrate or on a second substrate;
  
  and wherein the light absorbing layer is formed of a material that absorbs at least 50% of the light incident thereon and has a resistivity of from 2.5e12 ohm-cm (should it be ohm per cm squared?) to 1e15 ohm-cm.
- View Dependent Claims (48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 95, 96, 97, 98, 99, 100, 101, 102, 103)
- - 48. The spatial light modulator of claim 47, wherein the micromirrors correspond to a plurality of pixels in a direct-view or projection display.
  - 49. The spatial light modulator of claim 47, wherein the light absorbing layer is formed as a grid surrounding the electrodes.
  - 50. The spatial light modulator of claim 47, wherein the light absorbing layer is formed as a series of discrete light-absorbing areas on the electrodes.
  - 51. The spatial light modulator of claim 48, wherein the first substrate is bonded to a light transmissive substrate in a substrate assembly.
  - 52. The spatial light modulator of claim 47, wherein the light absorbing layer is black in color.
  - 53. The spatial light modulator of claim 47, wherein the light absorbing layer absorbs at least 50% of the light incident thereon.
  - 54. The spatial light modulator of claim 53, wherein the light absorbing layer absorbs at least 75% of the light incident thereon.
  - 55. The spatial light modulator of claim 54, wherein the light absorbing layer absorbs at least 85% of the light incident thereon.
  - 56. The spatial light modulator of claim 47, wherein the light absorbing layer covers substantially all of the first substrate.
  - 57. The spatial light modulator of claim 47, wherein the number of micromirrors in the array is from 6,000 to about 6 million.
  - 58. The spatial light modulator of claim 47, wherein the second substrate is an optically transmissive substrate.
  - 59. The spatial light modulator of claim 58, wherein the second substrate is glass, borosilicate, tempered glass, quartz or sapphire.
  - 60. The spatial light modulator of claim 47, wherein the second substrate is a glass or quartz substrate.
  - 61. The spatial light modulator of claim 47, wherein the first substrate is a dielectric or semiconductor substrate.
  - 62. The spatial light modulator of claim 61, wherein the first substrate comprises GaAs or silicon.
  - 63. The spatial light modulator of claim 47, wherein the first and second substrates are bonded together with an adhesive.
  - 64. The spatial light modulator of claim 47, wherein the second substrate is a glass substrate.
  - 65. The spatial light modulator of claim 47, wherein the micromirrors are held by at least a post on the second substrate that is optically transmissive.
  - 66. The spatial light modulator of claim 47, wherein the micromirrors are formed on the second substrate.
  - 67. The spatial light modulator of claim 66, wherein the circuitry and plurality of electrodes are disposed on the first substrate, wherein the micromirrors are positioned above and spaced apart from the plurality of electrodes on the second substrate.
  - 68. The spatial light modulator of claim 47, wherein the micromirrors are formed on the first substrate.
  - 69. The spatial light modulator of claim 47, wherein each micromirror has jagged or zig-zag edges.
  - 70. The spatial light modulator of claim 47, further comprising a stiction reducing agent on one or both substrates.
  - 71. The spatial light modulator of claim 47, wherein the light absorbing layer comprises black nickel or black chrome.
  - 72. The spatial light modulator of claim 47, wherein the light absorbing layer comprises a black or dark colored metal or metal alloy.
  - 73. The spatial light modulator of claim 47, wherein the light absorbing layer is a carbon containing polymer.
  - 74. The spatial light modulator of claim 47, wherein the light absorbing layer is deposited by sputtering.
  - 75. The spatial light modulator of claim 47, wherein the light absorbing layer is a carbon containing film.
  - 76. The spatial light modulator of claim 47, wherein the light absorbing layer comprises a carbon compound.
  - 77. The spatial light modulator of claim 47, wherein the light absorbing layer is a multilayer film.
  - 78. The spatial light modulator of claim 47, further comprising a light absorbing frame around each die area.
  - 79. The spatial light modulator of claim 47, wherein the light absorbing layer comprises at least two different light absorbing materials.
  - 80. The spatial light modulator of claim 47, further comprising a set of light-absorbing strips proximate to gaps between adjacent micromirrors.
  - 81. The spatial light modulator of claim 78, further comprising a light-absorbing frame surrounding each micromirror.
  - 82. The spatial light modulator of claim 81, wherein the light absorbing frame surrounding each micromirror is on the same side of the second substrate as the micromirrors.
  - 83. The spatial light modulator of claim 81, wherein the light absorbing frame surrounding each die is on a side of the second substrate opposite to the side on which the micromirrors are formed.
  - 84. The spatial light modulator of claim 47, wherein the first substrate is bonded to the second substrate at a distance of less than 100 microns from the second substrate.
  - 85. The spatial light modulator of claim 84, wherein the first substrate is bonded to the second substrate at a distance of less than 10 microns from the second substrate.
  - 86. The spatial light modulator of claim 47, wherein the light absorbing layer covers the electrodes but not gaps between the electrodes.
  - 95. The spatial light modulator of claim 47, wherein the light absorbing layer absorbs at least 50% of the light incident thereon.
  - 96. The spatial light modulator of claim 53, wherein the light absorbing layer absorbs at least 75% of the light incident thereon.
  - 97. The spatial light modulator of claim 54, wherein the light absorbing layer absorbs at least 85% of the light incident thereon.
  - 98. The spatial light modulator of claim 47, wherein the light absorbing layer comprises black nickel or black chrome.
  - 99. The spatial light modulator of claim 47, wherein the light absorbing layer comprises a black or dark colored metal or metal alloy.
  - 100. The spatial light modulator of claim 47, wherein the light absorbing layer is a carbon containing polymer.
  - 101. The spatial light modulator of claim 47, wherein the light absorbing layer is deposited by sputtering.
  - 102. The spatial light modulator of claim 47, wherein the light absorbing layer is a carbon containing film.
  - 103. The spatial light modulator of claim 47, wherein the light absorbing layer comprises a carbon compound.

87. A method for making a spatial light modulator, comprising:
- providing a first substrate;
  
  forming an array of circuitry and electrodes on the first substrate;
  
  forming a light absorbing layer on the first substrate from a material that absorbs at least 50% of the light incident thereon and has a resistivity of from 2.5e12 ohm-cm to 1e15 ohm-cm; and
  
  forming an array of deflectable reflective elements on the first or on a second substrate; and
  
  if on the second substrate, bonding the first and second substrates together to form a substrate assembly.

88. A method for making a spatial light modulator, comprising:
- providing a first substrate and a second substrate;
  
  forming a plurality of electrodes each of which is associated with a circuitry of an array of circuitry on the second substrate;
  
  depositing a discrete light absorbing area on each of the electrodes to form coated electrodes;
  
  forming a plurality of deflectable reflective elements on the first or second substrate; and
  
  disposing the first and second substrates such that each deflectable reflective element is positioned proximate to a coated electrode such that the deflectable reflective element is capable of being electrostatically actuated by the coated electrode.
- View Dependent Claims (89, 90, 91, 92, 93, 94)
- - 89. The method of claim 88, wherein the deflectable reflective elements are formed on the first substrate
  - 90. The method of claim 88, wherein the deflectable reflective elements are formed on the second substrate.
  - 91. The method of claim 88, wherein each deflectable reflective element is disposed proximate to a plurality of coated electrodes, the plurality of coated electrodes capable of alternately actuating the proximate deflectable reflective element. (Greg—
    - is this a claim for multi-electrodes for one mirror?)
  - 92. The method of claim 88, wherein the discrete light absorbing areas are electrically conductive.
  - 93. The method of claim 88, wherein each coated electrode is positioned next to a single deflectable reflective element.
  - 94. The method of claim 88, wherein the first and second substrates are bonded together.

104. A method for making a spatial light modulator, comprising:
- providing a substrate;
  
  forming a plurality of electrodes each being associated with a circuitry of a plurality of circuitry on the substrate;
  
  depositing a discrete light absorbing area on each of the electrodes to form coated electrodes;
  
  forming a plurality of deflectable reflective elements positioned above the coated electrodes.
- View Dependent Claims (105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118)
- - 105. The method of claim 104, wherein the deflectable reflective elements are formed on the substrate.
  - 106. The method of claim 104, wherein the deflectable reflective elements are formed on a second substrate positioned proximate to the substrate.
  - 107. The method of claim 104, wherein each deflectable reflective element is disposed proximate to a plurality of coated electrodes, the plurality of coated electrodes capable of alternately actuating the proximate deflectable reflective element.
  - 108. The method of claim 104, wherein the discrete light absorbing areas are electrically conductive.
  - 109. The method of claim 104, wherein each electrode is positioned next to a single deflectable element.
  - 110. The spatial light modulator of claim 104, wherein the light absorbing layer absorbs at least 50% of the light incident thereon.
  - 111. The spatial light modulator of claim 110, wherein the light absorbing layer absorbs at least 75% of the light incident thereon.
  - 112. The spatial light modulator of claim 111, wherein the light absorbing layer absorbs at least 85% of the light incident thereon.
  - 113. The spatial light modulator of claim 104, wherein the light absorbing layer comprises black nickel or black chrome.
  - 114. The spatial light modulator of claim 104, wherein the light absorbing layer comprises a black or dark colored metal or metal alloy.
  - 115. The spatial light modulator of claim 104, wherein the light absorbing layer is a carbon containing polymer.
  - 116. The spatial light modulator of claim 104, wherein the light absorbing layer is deposited by sputtering.
  - 117. The spatial light modulator of claim 104, wherein the light absorbing layer is a carbon containing film.
  - 118. The spatial light modulator of claim 104, wherein the light absorbing layer comprises a carbon compound.

119. A method for making a spatial light modulator, comprising:
- providing a first substrate and a second substrate;
  
  forming a plurality of electrodes each being associated with a circuitry of a plurality of circuitry on the second substrate;
  
  depositing light absorbing material to surround the electrodes such that the light absorbing material partially covers the second substrate;
  
  forming a plurality of deflectable reflective elements on the first substrate; and
  
  disposing the first and second substrates such that each deflectable reflective element is positioned proximate to an electrode such that the deflectable reflective element is capable of being electrostatically actuated by the electrode.
- View Dependent Claims (120, 121, 122, 123, 124, 125)
- - 120. The method of claim 119, wherein the deflectable reflective elements are formed on the first substrate.
  - 121. The method of claim 119, wherein the deflectable reflective elements are formed on the second substrate.
  - 122. The method of claim 119, wherein each deflectable element is formed or positioned proximate to a plurality of coated electrodes, the plurality of coated electrodes capable of alternately actuating the defectable element.
  - 123. The method of claim 119, wherein the discrete light absorbing areas are formed from electrically conductive material.
  - 124. The method of claim 119, wherein the first and second substrates are bonded together.
  - 125. The method of claim 119, wherein the step of disposing the first and second substrates comprises bonding the first and second substrates together such that each coated electrode is positioned next to a single deflectable element.

126. A method for making a spatial light modulator, comprising:
- providing a substrate;
  
  forming a plurality of electrodes each with associated circuitry on the substrate;
  
  depositing light absorbing material to surround the electrodes such that the light absorbing material partially covers the substrate; and
  
  forming a plurality of deflectable reflective elements positioned above the coated electrodes.
- View Dependent Claims (128, 129, 130, 132)
- - 128. The method of claim 126, further comprising depositing a sacrificial material on the substrate, depositing and patterning a micromechanical structural material on the sacrificial material to form micromirrors, and removing the sacrificial material in order to release the micromirrors.
  - 129. The method of claim 126, further comprising forming micromirrors on a second substrate and bonding the substrate and the second substrate together.
  - 130. The method of claim 126, wherein the light absorbing material is electrically conductive.
  - 132. The method of claim 129, wherein a single micromirror element is formed proximate to one or more coated electrodes.

127. A method for making a spatial light modulator, comprising:
- providing a substrate;
  
  forming a plurality of circuitry and electrodes on the substrate;
  
  depositing and patterning a photoresist on the substrate so as to provide areas with and without the photoresist on the substrate;
  
  depositing a light absorbing material so as to fill the areas without photoresist with the light absorbing material; and
  
  removing the photoresist so as to leave selected areas on the substrate with light absorbing material.
- View Dependent Claims (131, 133)
- - 131. The method of claim 127, wherein a single micromirror element is formed proximate to a plurality of electrodes.
  - 133. The method of claim 127, wherein the light absorbing material is selectively deposited by depositing a photoresist, patterning the photoresist so as to remove photoresist in selected areas, depositing the light absorbing material, and removing remaining photoresist.

134. A method for making a spatial light modulator, comprising:
- forming an array of circuitry and electrodes on a first substrate;
  
  forming a light absorbing layer on the first substrate to reduce reflections from the circuitry and/or electrodes on the substrate; and
  
  forming an array of deflectable reflective elements on the first substrate or on a second substrate;
  
  wherein the light absorbing layer is formed of a thin film ceramic, wherein the thin film ceramic is deposited by chemical vapor deposition or physical vapor deposition.
- View Dependent Claims (135, 136, 137, 138)
- - 135. The method of claim 134, wherein the thin film ceramic is a carbon compound.
  - 136. The method of claim 134, wherein the thin film is a chromium compound.
  - 137. The method of claim 135, wherein the carbon compound is CN, CAlN, TiCN, a-DLC, SiC, TiAlCN or WC.
  - 138. The method of claim 137, wherein the light absorbing layer is black.

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Current Assignee
Texas Instruments, Inc.
Original Assignee
Reflectivity, Inc. (Texas Instruments, Inc.)
Inventors
Huibers, Andrew G., Richards, Peter W.

Granted Patent

US 6,958,846 B2
Time in Patent Office

Days
Field of Search
US Class Current

349/25
CPC Class Codes

B82Y 30/00   Nanotechnology for material...

G02B 26/0841   the reflecting element bein...

H04N 5/7458   the modulator being an arra...

Spatial light modulators with light absorbing areas

First Claim

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Abstract

214 Citations

140 Claims

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Spatial light modulators with light absorbing areas

First Claim

4 Assignments

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Accused Products

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Abstract

214 Citations

140 Claims

Specification

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Solutions

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