Micromirror array device and a method for making the same

• US 7,092,143 B2
• Filed: 10/19/2004
• Issued: 08/15/2006
• Est. Priority Date: 10/19/2004
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Heureux, Peter
• Primary Examiner(s): Thompson, Timothy
• Assistant Examiner(s): Fang, Jerry
• Application Number:
  US10/969,251
• Publication Number:
  US 20060082858A1
• Time in Patent Office: 665 Days
• Field of Search: 359/291, 359/290, 359/223, 359/224, 359/295
• US Class Current: 359/291
• 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: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

The spatial light modulator of the present invention comprises an array of micromirrors, each of which has a reflective deflectable mirror plate. A set of posts are provided for holding the mirror plates on a substrate, but not all micromirrors of the micromirror array have posts.

Claims

1. A projection system, comprising:

an illumination system providing a light beam to be incident on a spatial light modulator;

the spatial light modulator that comprises;

an array of micromirrors, each micromirror positioned at a pixel location, further comprising;

a first micromirror at a first pixel location comprising;

a deflectable reflective mirror plate attached to a deformable hinge that is supported by a post on a substrate at the first pixel location; and

a second micromirror at a second pixel location comprising;

a deflectable reflective mirror plate attached to a deformable hinge that is not supported by a post on the substrate at the second pixel location; and

an optical element for directing light to or from the spatial light modulator.

2. The projection system of claim 1, further comprising a display target.

3. The projection system of claim 1, comprising a first optical element for directing the light beam to the spatial light modulator;

and comprising a second optical element for projecting the light beam from the spatial light modulator onto a target.

4. The projection system of claim 1, having a resolution of 1024×

768 or higher.

5. The projection system of claim 1, wherein a plurality of first micromirrors are provided with at least two posts and a plurality of second micromirrors are provided with less than two posts, wherein the ratio of the number of first micromirrors to the total number of micromirrors is 1:

2 or less.

6. The projection system of claim 1, wherein a plurality of third micromirrors are provided with at least one post and a plurality of forth micromirrors are not provided with a post, wherein the ratio of the number of first micromirrors to the total number of micromirrors is 1:

3 or less.

7. The projection system of claim 6, wherein the ratio is 1:

4 or less.

8. The projection system of claim 1, wherein the deformable hinge comprises TiN_x or TiSi_xN_y.

9. The projection system of claim 8, wherein the deformable hinge comprises SiN_x.

10. The projection system of claim 1, wherein the hinge is a multilayered structure.

11. The projection system of claim 1, wherein the mirror plate is a multilayered structure, comprising a conducting layer.

12. The projection system of claim 11, wherein the conducting layer is aluminum.

13. The projection system of claim 11, wherein the mirror plate further comprises a ceramic layer that comprises SiO_x.

14. The display system of claim 1, wherein the illumination system comprises:

a light source;

a light pipe; and

a color filter.

15. The display system of claim 14, wherein the light pipe is positioned between the light source and the color filter.

16. The display system of claim 14, wherein the color filter is positioned between the light source and the light pipe.

17. The display system of claim 14, wherein the color filter is a color wheel having primary colors.

18. The display system of claim 1, wherein each micromirror of the micromirror array has a hinge support by which the hinge of the micromirror is held.

19. The display system of claim 18, wherein the mirror plate and the hinge are in separate planes parallel to the substrate.

20. The display system of claim 18, wherein the hinge and the mirror plate are in the same plane parallel to the substrate.

21. The display system of claim 1, wherein the mirror plate is positioned between the hinge and the substrate of the micromirror.

22. The display system of claim 18, wherein the hinge supports of a set of the array of micromirrors are interconnected together forming a hinge support strip.

23. The display system of claim 18, wherein the hinge supports of a set of the array of micromirrors are interconnected together forming a hinge support frame.

24. The display system of claim 18, wherein the hinge supports of a set of the array of micromirrors are interconnected together forming a hinge support grid.

25. The display system of claim 1, wherein the mirror plate and/or hinge is made of single crystal silicon patterned from a silicon substrate.

26. The display system of claim 1, wherein the post of the first mirror plate comprises a light absorbing layer thereon for absorbing light from the illumination system that is incident thereon.

27. The display system of claim 1, wherein the first mirror plate is held by the post on a substrate transmissive to visible light.

28. The display system of claim 1, wherein the first mirror plate is held by the post on an opaque substrate.

29. The display system of claim 28, wherein the opaque substrate is a silicon substrate.

30. The display system of claim 1, wherein the posts comprises a portion having a light absorbing material coated thereon for reducing light scattering.

31. A projection system, comprising:

an illumination system providing a light beam for the system;

a spatial light modulator that comprises;

an array of micromirrors, at least one of which comprises;

a deflectable reflective mirror plate attached to a deformable hinge that is directly supported by a post on a substrate; and

at least another one of which comprises;

a deflectable reflective mirror plate attached to a deformable hinge that is not directly supported by a post on the substrate;

an optical element for directing light to or from the spatial light modulator.

32. A projection system comprising:

a light source for providing light onto an array of micromirrors;

an array of micromirrors comprising a first group and a second group, wherein micromirrors of the first group each have a micromirror plate and two posts adjacent the micromirror plate for deflectably supporting the micromirror plate, and wherein micromirrors of the second group each have a micromirror plate and a single post adjacent the micromirror plate for deflectably supporting the micromirror plate.

33. The projection system of claim 32, wherein the array of micromirrors comprises a third group each having a micromirror plate and no posts adjacent the micromirror plate, wherein the third group of micromirrors is connected to adjacent micromirrors for support.

34. A display system, comprising:

an illumination system;

a spatial light modulator that comprises;

a substrate;

an array of reflective deflectable mirror plates on the substrate;

an array of hinges and hinge supports, each hinge being held by the hinge support and attached to a mirror plate such that the mirror plate can rotate relative to the substrate; and

wherein a first hinge support of said hinge supports has connected thereto a post connecting the first hinge support to the substrate, and wherein a second hinge support of said hinge supports has no post directly connecting the second hinge support to the substrate; and

an optical element for directing light to or from the spatial light modulator.

35. The display system of claim 34, further comprising a display target.

36. The display system of claim 34, wherein each post directly connects one of the array of hinge supports to the substrate, and wherein at least one of the array of hinge supports is not directly connected to a post.

37. The display system of claim 34, wherein the micromirrors having posts connected thereto are located in the micromirror array complying with a predetermined pattern.

38. The display system of claim 36, wherein the predetermined pattern comprises that a particular number of micromirrors having no posts connected thereto is positioned between two consecutive micromirrors both having at least one post directly connected thereto along a particular direction.

39. The display system of claim 38, wherein the particular number is a random number.

40. The display system of claim 38, wherein the particular number is determined based upon a mechanical property of the hinges supports and hinges.

41. The display system of claim 34, wherein the illumination system comprises:

a light source;

a light pipe; and

a color filter.

42. The display system of claim 41, wherein the light pipe is positioned between the light source and the color filter.

43. The display system of claim 41, wherein the color filter is positioned between the light source and the light pipe.

44. The display system of claim 41, wherein the color filter is a color wheel having primary colors.

45. The display system of claim 34, wherein the mirror plate and the hinge of the micromirror are in separate planes parallel to the substrate.

46. The display system of claim 34, wherein the hinge and the mirror plate are in the same plane parallel to the substrate.

47. The display system of claim 34, wherein the mirror plate is positioned between the hinge and the substrate of the micromirror.

48. The display system of claim 34, wherein the hinge supports of a set of the array of micromirrors are interconnected together forming a hinge support strip.

49. The display system of claim 34, wherein the hinge supports of a set of the array of micromirrors are interconnected together forming a hinge support frame.

50. The display system of claim 34, wherein the hinge supports of a set of the array of micromirrors are interconnected together forming a hinge support grid.

51. The projection system of claim 34, having a resolution of 1024×

768 or higher.

52. The projection system of claim 34, wherein a plurality of first micromirrors are provided with at least two posts and a plurality of second micromirrors are provided with less than two posts, wherein the ratio of the number of first micromirrors to the total number of micromirrors is 1:

2 or less.

53. The projection system of claim 34, wherein a plurality of third micromirrors are provided with at least one post and a plurality of forth micromirrors are not provided with a post, wherein the ratio of the number of first micromirrors to the total number of micromirrors is 1:

3 or less.

54. The projection system of claim 53, wherein the ratio is 1:

4 or less.

55. The projection system of claim 34, wherein the hinge comprises TiN_x.

56. The projection system of claim 34, wherein the deformable hinge comprises SiN_x.

57. The projection system of claim 34, wherein the hinge is a multilayered structure.

58. The projection system of claim 57, wherein the mirror plate is a multilayered structure, comprising a conducting layer.

59. The projection system of claim 58, wherein the conducting layer is aluminum.

60. The projection system of claim 58, wherein the mirror plate further comprises a ceramic layer that comprises SiO_x.

61. A spatial light modulator, comprising:

a substrate;

an array of reflective deflectable mirror plates on the substrate;

a hinge support frame composed of a set of hinge supports, each hinge support holding a deformable hinge to which a mirror plate of the array of mirror plates is attached; and

a plurality of posts positioned between the hinge frames and the substrate for supporting the hinge supports on the substrate such that the mirror plate can be rotated on the substrate;

wherein at least one hinge support is directly connected to less than two posts.

62. A projection system, comprising:

an illumination system; and

a spatial light modulator comprising;

a group of first micromirror devices each of which comprises a deflectable reflective mirror plate, a deformable hinge, and at least two posts for holding the mirror plate and hinge above a substrate; and

a group of second micromirror devices each of which comprises a deflectable mirror plate, a deformable hinge, and at most one post for holding the mirror plate and hinge above a substrate;

wherein a ratio of the numbers of the first micromirrors to the second micromirrors is 1;

2 or less.

63. The projection system of claim 62, wherein the number of the first micromirrors is 70% or less of the total number of micromirrors in the micromirror array.

64. The projection system of claim 63, wherein the number of the first micromirrors is 50% or less of the total number of micromirrors in the micromirror array.

65. The projection system of claim 63, wherein the number of the second micromirrors is 30% or more of the total number of micromirrors in the micromirror array.

66. The projection system of claim 63, wherein the number of the second micromirrors is 50% or more of the total number of micromirrors in the micromirror array.

67. The projection system of claim 62, wherein the group of second micromirrors further comprises a subgroup of third micromirrors each of which having no post, and a subgroup of fourth micromirrors each of which has a single post, wherein the number of the third micromirrors is 10% or less of the total number of the second micromirrors in the group.

68. The projection system of claim 67, wherein the number of the third micromirrors is 5% or less of the total number of the second micromirrors in the group.

69. The projection system of claim 67, wherein the number of the third micromirrors is 1% or less of the total number of the second micromirrors in the group.

70. The projection system of claim 67, wherein the number of the fourth micromirrors is 95% or more of the total number of the second micromirrors in the group.

71. The projection system of claim 67, wherein the number of the fourth micromirrors is 85% or more of the total number of the second micromirrors in the group.

72. The projection system of claim 67, wherein the number of the fourth micromirrors is 75% or more of the total number of the second micromirrors in the group.

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

depositing a first and second sacrificial layer on a substrate;

forming a array of mirror plates and a plurality of posts for the mirror plates on the first and second sacrificial layer, wherein a ratio of the number of the plurality of posts to the total number n of mirror plates is less than (n+1)/n;

forming a hinge for each mirror plate; and

removing the first and second sacrificial layer so as to release the mirror plates.

74. The method of claim 73, wherein the first and second sacrificial layer comprises amorphous silicon;

and wherein the step of removing the first and second sacrificial layer further comprising;

removing the amorphous silicon with a vapor phase etchant.

75. The method of claim 74, wherein the etchant is an spontaneous vapor phase etchant.

76. The method of claim 75, wherein the etchant is an interhalogen.

77. The method of claim 75, wherein the etchant is a noble gas halide.

78. The method of claim 75, wherein the etchant is HF.

79. The method of claim 73, wherein the ratio is less than (n+1)/2n.