Micromirror array assembly with in-array pillars

• US 20050275930A1
• Filed: 06/15/2004
• Published: 12/15/2005
• Est. Priority Date: 06/15/2004
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Tarn, Terry, Huibers, Andrew G., Richards, Peter, Patel, Satyadev, Dehlinger, Dietrich
• Granted Patent: US 7,787,170 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: B81C 3/001 Bonding of two components
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: Y10S 359/90 Methods
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor

Abstract

The present invention provides a microstructure device comprising multiple substrates with the components of the device formed on the substrates. In order to maintain uniformity of the gap between the substrates, a plurality of pillars is provided and distributed in the gap so as to prevent decrease of the gap size. The increase of the gap size can be prevented by bonding the pillars to the components of the microstructure. Alternatively, the increase of the gap size can be prevented by maintaining the pressure inside the gap below the pressure under which the microstructure will be in operation. Electrical contact of the substrates on which the micromirrors and electrodes are formed can be made through many ways, such as electrical contact areas, electrical contact pads and electrical contact springs.

Claims

1. A microelectromechanical (MEMS) device, comprising:

a first substrate and a second substrate;

a plurality of MEMS elements formed on the first substrates; and

a plurality of pillars disposed between the second substrate and the MEMS elements.

2. The device of claim 1, wherein the pillars are positioned within the MEMS elements.

3. The device of claim 1, wherein the pillars are positioned within an area covered by the MEMS elements.

4. The device of claim 1, wherein the pillars don'"'"'t connect the MEMS elements electrically to circuitry for addressing the MEMS elements.

5. The device of claim 1, wherein each of the plurality of pillars comprises an insulating portion that insulates the MEMS elements from circuitry provided for addressing the MEMS elements.

6. The device of claim 1, further comprising:

a sealing material disposed between the substrates for bonding the substrates.

7. The device of claim 6, wherein the bonded substrate and the sealing material therebetween form a hermetically sealed space.

8. The device of claim 3, wherein the hermetically sealed space has a pressure lower than 1 atmosphere.

9. The device of claim 1, wherein the functional components comprise:

an array of micromirrors on the first or the second substrate; and

an array of electrodes and circuitry on the first or the second substrate for deforming the micromirrors.

10. The device of claim 9, wherein the micromirror further comprising:

a post on the substrate;

a hinge held by the post on the substrate; and

a reflective mirror plate attached to the hinge such that the mirror plate is operable to rotate on the substrate.

11. The device of claim 10, wherein the pillar is connected to the post of the micromirror.

12. The device of claim 10, wherein each micromirror has two adjacent posts on the substrate, each post being connected to a pillar.

13. The device of claim 1, wherein the pillars is distributed within an area between the substrates according to a distribution of deformation in the deformable substrate under the pressure.

14. The device of claim 11, wherein the contact point of the pillar to the post is substantially in the middle of the substrates.

15. The device of claim 11, wherein the contact point of the pillar to the post is in the same plane as the hinge.

16. The device of claim 11, wherein the contact point of the pillar to the post is not in the same plane as the hinge.

17. The device of claim 11, wherein the mirror plate, the hinge and the contact point of the pillar to the hinge are on the same plane.

18. The device of claim 11, wherein the pillar has a first component that is connected to the post of the micromirror and a second component that is connected to the first component of the pillar and the substrate on which the electrodes are disposed.

19. The device of claim 18, wherein the first component of the pillar has a smaller dimension than the second component of the pillar.

20. The device of claim 11, wherein the pillar has a smaller area at the contact point of the pillar to the post than the area of the post at the contact point.

21. The device of claim 1, wherein the pillar comprises a material that has a coefficient of thermal expansion (CTE) matches that of the material of the post.

22. The device of claim 1, wherein the pillar comprises a material that has a thermal conductivity equal to or less than that of the post.

23. The device of claim 1, further comprising:

an optical coating film on a surface of the substrate on which the micromirrors are disposed.

24. The device of claim 1, further comprising:

a getter material disposed on one of the two substrates for absorbing contaminants.

25. The device of claim 24, wherein the getter is disposed within a trench on the substrate having the micromirrors disposed thereon.

26. The device of claim 6, wherein the sealing material further comprises:

a first metallization material disposed on a sacrificial material that is disposed on the substrate on which the micromirrors are formed.

27. The device of claim 26, wherein the sealing material further comprises:

a second metallization material disposed on a layer composed of the material of the pillar, wherein said layer and the second metallization material are disposed on the substrate on which the electrodes are disposed.

28. The device of claim 6, wherein the sealing material has a height that is substantially equal to a summation of the heights of the micromirror and the pillar.

29. The device of claim 6, wherein the substrate having the electrodes and circuitry thereon further comprises:

a passivation layer on a surface of the said substrate.

30. The device of claim 6, further comprising:

a package substrate, wherein the substrate having the electrodes and circuitry is attached to the package substrate; and

a package lid on the package substrate for covering the micromirror device.

31. The device of claim 30, further comprising:

a shim that is placed between the package substrate and the substrate having the micromirrors.

32. The device of claim 31, further comprising:

a substrate insert between the package substrate and the substrate having the electrodes and circuitry.

33. A spatial light modulator for use in a projection system, comprising:

a micromirror array device, comprising;

a first substrate having thereon an array of micromirrors;

a second substrate having an array of electrodes for deforming the micromirrors; and

a plurality of pillars disposed between the substrates such that the first substrate is connected to the second substrate via the micromirror and the pillar for maintaining a uniform gap between the substrates.

34. The spatial light modulator of claim 33, further comprising:

a sealing material disposed between the substrates for bonding the substrates.

35. The spatial light modulator of claim 34, wherein the bonded substrate and the sealing material therebetween form a hermetically sealed space.

36. The spatial light modulator of claim 35, wherein the hermetically sealed space has a pressure lower than 1 atmosphere.

37. The spatial light modulator of claim 33, wherein the micromirror further comprising:

a post on the first substrate;

a hinge held by the post on the first substrate; and

a reflective mirror plate attached to the hinge such that the mirror plate is operable to rotate on the first substrate.

38. The spatial light modulator of claim 37, wherein the pillar is connected to the post of the micromirror.

39. The spatial light modulator of claim 38, wherein each micromirror has two posts on the substrate, each post being connected to a pillar.

40. The spatial light modulator of claim 33, wherein the pillars is distributed within an area between the substrates according to a distribution of deformation in the first substrate under a pressure.

41. The spatial light modulator of claim 38, wherein the contact point of the pillar to the post is in the same plane as the hinge.

42. The spatial light modulator of claim 38, wherein the contact point of the pillar to the post is not in the same plane as the hinge.

43. The spatial light modulator of claim 38, wherein the mirror plate, the hinge and the contact point of the pillar to the hinge are on the same plane.

44. The spatial light modulator of claim 38, wherein the pillar has a first component that is connected to the post of the micromirror and a second component that is connected to the first component of the pillar and the substrate on which the electrodes are disposed.

45. The spatial light modulator of claim 33, wherein the pillar comprises a material that has a coefficient of thermal expansion matches that of the material of the post.

46. The spatial light modulator of claim 33, wherein the pillar comprises a material that has a thermal conductivity equal to or less than that of the post.

47. The spatial light modulator of claim 33, further comprising:

an optical coating film on a surface of the substrate on which the micromirrors are disposed.

48. The spatial light modulator of claim 33, further comprising:

a getter material disposed on one of the two substrates for absorbing contaminants.

49. The spatial light modulator of claim 33, wherein the sealing material further comprises:

a first metallization material disposed on a sacrificial material that is disposed on the substrate on which the micromirrors are formed.

50. The spatial light modulator of claim 34, wherein the sealing material further comprises:

a second metallization material disposed on a layer composed of the material of the pillar, wherein said layer and the second metallization material are disposed on the substrate on which the electrodes are disposed.

51. A micromirror device, comprising:

a first substrate;

a post on the substrate;

a mirror plate attached to a hinge that is held by the post on the substrate such that the mirror plate rotates on the substrate;

a pillar on the mirror plate and in connection with the post; and

a second substrate having an electrode and circuitry disposed thereon for rotating the mirror plate, wherein the second substrate is disposed on the pillar and connected to the pillar such that the distance between the first and second substrate is maintained at a substantially constant value.

52. The micromirror device of claim 51, wherein the pillar is connected to the post of the micromirror.

53. The micromirror device of claim 52, wherein the connect point of the pillar to the post is in the same plane as the hinge.

54. The micromirror device of claim 52, wherein the connect point of the pillar to the post is not in the same plane as the hinge.

55. The micromirror device of claim 53, wherein the connect point of the pillar to the post is substantially in the middle between the substrates.

56. The micromirror of claim 51, further comprising another post on the first substrate for holding the hinge.

57. The micromirror of claim 55, wherein said another post is connected to another pillar that is placed between the substrates and connected to the second substrate.

58. The micromirror of claim 56, wherein said another pillar has a different dimension as the pillar.

59. The micromirror of claim 51, wherein the pillar has a first component that connects the post of the micromirror and a second component that is connected to the first component of the pillar and the second substrate.

60. The micromirror of claim 51, wherein the pillar has a material having a coefficient-of-thermal-expansion that matches that of the post.

61. The micromirror of claim 51, wherein the pillar has a material having a thermal conductivity that is equal to or higher than that of the post.

62. A method of making a spatial light modulator, the method comprising:

forming an array of micromirrors on first substrate;

forming an array of electrodes and circuitry on second substrate;

forming a plurality of pillars on the second substrate;

aligning each pillar with one of the micromirrors; and

bonding the substrates.

63. The method of claim 62, wherein the step of forming the array of micromirrors further comprises:

depositing a first sacrificial layer on a first substrate;

forming an array of mirror plates on the first sacrificial layer;

depositing a second sacrificial layer on the mirror plates; and

forming an array of posts and hinges on the substrate such that the mirror plate is attached to the hinge, and the hinge is held on the first substrate by the post.

64. The method of claim 63, wherein the step of forming the plurality of pillars further comprises:

depositing a pillar material on the second substrate; and

patterning the deposited pillar material so as to form the pillars.

65. The method of claim 64, wherein the step of aligning the pillar with the micromirror further comprising:

aligning the pillar with the post of the micromirror such that the pillar is connected to the post.

66. A micromirror array device, comprising

a substrate having thereon an array of micromirrors, further comprising:

at least two electrical contact pads, each of which is electrically connected to the micromirrors such that am electrical resistance of the micromirrors of the array can be measured through the electrical contact pads; and

an array of electrodes associated with the micromirrors for deflecting the micromirrors.

67. The device of claim 66, wherein the electrodes are disposed on another substrate other than the substrate having the micromirrors.

68. The device of claim 67, wherein the two substrates are bonded together through a sealing material.

69. The device of claim 68, further comprising:

a shim that electrically connects the electrical contact pads and a package substrate to which the bonded substrates are attached such that the electrical contact pads are extended to the package substrate.

70. The device of claim 68, wherein the substrate having the electrodes further comprises:

a multiplicity of electrical contact areas at a plurality of locations corresponding to the locations of the electrical contact pads on the substrate having the micromirrors such that, when the two substrates are bonded together, the electrical contact pads are overlapped with the electrical contact areas.

71. A spatial light modulator, comprising:

an array of micromirrors on a first substrate;

an array of electrodes and circuitry on a second substrate;

a first sealing material that hermetically bonds the first and second substrates; and

a second sealing material other than the first seal material contracting the first and second substrate for enhancing the hermetic seal with the first sealing material.

72. The spatial light modulator of claim 71, wherein the first substrate is glass that is transmissive to visible light.

73. The spatial light modulator of claim 71, wherein the first sealing material is metal.

74. The spatial light modulator of claim 71, wherein the second sealing material is epoxy.

75. The spatial light modulator of claim 71, wherein the first sealing material forms a sealing ring between the first and second substrates.

76. The spatial light modulator of claim 75, wherein the second sealing material is disposed within the sealing ring.

77. The spatial light modulator of claim 75, wherein the second sealing material is disposed outside the sealing ring.

78. The spatial light modulator of claim 71, wherein the second sealing material is operable to hermetically seal the first and second substrates.

79. A microelectromechanical device, comprising:

a first and second substrate bonded together;

an array of MEMS elements formed on the first substrate and disposed between the substrates;

an array of electrodes and circuitry disposed between the bonded substrates but spaced apart from the array of MEMS elements; and

a plurality of pillars disposed between the second substrate and the MEMS elements.

80. The device of claim 79, wherein the pillars are positioned within the MEMS elements.

81. The device of claim 79, wherein the pillars positioned within an area covered by the MEMS elements.

82. The device of claim 79, wherein the pillars don'"'"'t connect the MEMS elements electrically.

83. The device of claim 79, wherein each of the plurality of pillars comprises an insulating portion.

84. The device of claim 79, wherein first substrate is light transmissive.

85. The device of claim 84, wherein the light transmissive substrate is glass.

86. The device of claim 79, wherein the first and second substrate is hermetically bonded.

87. The device of claim 79, wherein the pillar is positioned proximate to a reflective deflectable element of the MEMS but does not directly connected thereto.

88. A method of forming a spatial light modulator for use in a display system, the method comprising:

forming a plurality of micromirrors on a light transmissive substrate, wherein each micromirror has a fixed portion and a movable portion;

forming a plurality of electrodes and circuitry on a semiconductor substrate; and

forming a pillar on the fixed portion of the micromirror and/or on the semiconductor substrate.

89. The method of claim 88, wherein the pillar is formed only on the semiconductor substrate.

90. The method of claim 88, wherein the pillar is formed only on the fixed portion of the micromirror.

91. The method of claim 88, wherein the pillar is formed on both of the fixed portion and the semiconductor substrate.

92. The method of claim 88, wherein the pillar is formed within an area covered by the micromirrors.

93. The method of claim 88, wherein the pillar comprises an insulating portion.

94. The method of claim 88, further comprising:

bonding the light transmissive substrate and the semiconductor substrate together to form an assembly such that the micromirrors, the electrodes and circuitry are positioned between the substrates.

95. The method of claim 94, wherein the step of bonding the light transmissive substrate and the semiconductor substrate further comprising:

hermetically bonding the light transmissive substrate and the semiconductor substrate.

96. The method of claim 95, wherein the step of hermetically bonding the light transmissive substrate and the semiconductor substrate further comprising:

hermetically bonding the semiconductor substrate and the light transmissive substrate such that a space between the hermetically bonded substrate has a pressure lower than 1 atmosphere.

97. The method of claim 94, wherein the step of hermetically bonding the light transmissive substrate and the semiconductor substrate further comprising:

bonding the semiconductor substrate and the light transmissive substrate while the micromirrors are not fully surrounded.

98. The method of claim 88, wherein the step of forming the micromirrors further comprising:

forming a plurality of mirror plates on the light transmissive substrate; and

forming a plurality of hinges on the light transmissive substrate such that the mirror plates and hinges are located on different planes parallel to the light transmissive substrate.