Micromirror elements, package for the micromirror elements, and projection system therefor

• US 6,962,419 B2
• Filed: 03/08/2001
• Issued: 11/08/2005
• Est. Priority Date: 09/24/1998
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Huibers, Andrew G.
• Primary Examiner(s): Dowling, William C.
• Application Number:
  US10/343,307
• Publication Number:
  US 20040125346A1
• Time in Patent Office: 1,706 Days
• Field of Search: 353/31, 353/98, 353/99, 359/198, 359/212, 359/222, 359/267, 359/291, 359/292, 359/298, 359/323, 348/742, 348/743, 348/771, 345/31, 345/108
• US Class Current: 353/99
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48472 the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/16195 Flat cap [not enclosing an internal cavity]
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

In order to minimize light diffraction along the direction of switching and more particularly light diffraction into the acceptance cone of the collection optics, in the present invention, micromirrors are provided which are not rectangular. Also, in order to minimize the cost of the illumination optics and the size of the display unit of the present invention, the light source is placed orthogonal to the rows (or columns) of the array, and/or the light source is placed orthogonal to a side of the frame defining the active area of the array. The incident light beam, though orthogonal to the sides of the active area, is not however, orthogonal to any substantial portion of sides of the individual micromirrors in the array. Orthogonal sides cause incident light to diffract along the direction of micromirror switching, and result in light ‘leakage’ into the ‘on’ state even if the micromirror is in the ‘off’ state. This light diffraction decreases the contrast ratio of the micromirror. The micromirrors of the present invention result in an improved contrast ratio, and the arrangement of the light source to micromirror array in the present invention results in a more compact system. Another feature of the invention is the ability of the micromirrors to pivot in opposite direction to on and off positions (the on position directing light to collection optics), where the movement to the on position is greater than movement to the off position. A further feature of the invention is a package for the micromirror array, the package having a window that is not parallel to the substrate upon which the micromirrors are formed. One example of the invention includes all the above features.

Claims

1. A method for spatially modulating a light beam, comprising directing a light beam from a light source to light collection optics via an array of micromirrors disposed to spatially modulate the light beam from the light source, the array formed on a substrate and each micromirror being in a first position when not modulated, modulating micromirrors in the array so that each micromirror moves to an on position that directs light to the light collection optics for the array, and moves to an off position for directing light away from the light collection optics, both said on and off positions being different from said first position, and wherein the on position is at a magnitude of an angle relative to the first position different from the magnitude of an angle when in the off position.

2. An optical micromechanical element formed on a substrate having an on position at a first magnitude of an angle relative to the substrate, having an off position at a second magnitude of an angle to the substrate, the first and second magnitudes being different, and having a third position substantially parallel to the substrate, both the on and off positions being defined by abutment of the optical micromechanical element against the substrate or against structure formed on said substrate.

3. The micromechanical element of claim 2, wherein landing electrodes are provided on the substrate against which the micromirror stops in the on and off positions.

4. The micromechanical element of claim 3, wherein one landing electrode is positioned higher relative to the substrate than another landing electrode.

5. The micromechanical element of claim 2, that is in a package, the package comprising a window that is at an angle to the substrate.

6. The micromechanical element of claim 5, wherein the package is a hermetic or partially hermetic package.

7. The micromechanical element of claim 5, further comprising a molecular scavenger in the package.

8. The micromechanical element of claim 5, further comprising a stiction reduction agent within the package.

9. The micromechanical element of claim 2, further comprising flexure hinges disposed in a gap between a plate of the micromirror element and the substrate.

10. The micromechanical element of claim 2, further comprising deflection electrodes for deflecting the element to the on or off position.

11. The micromechanical element of claim 10, wherein at least one deflection electrode is disposed for moving the element to the on position, and at least one deflection electrode is disposed for moving the element to the off position.

12. The micromechanical element of claim 2 that is a micromirror.

13. A method for modulating light, comprising:

reflecting light from an array of deflectable micromirrors disposed on a planar substrate;

said micromirrors tilted to either a first position or to a second position;

wherein the angle formed between said first position and the substrate,

and the angle formed between said second position and the substrate, are substantially different.

14. A method for modulating light, comprising:

a light source, a planar light modulator array comprising a deflectable elements and collection optics,

wherein the elements in the array are selectively configured in at least two states,

wherein the first state elements direct the light from the light source through a first angle into the collection optics,

and in the second state elements direct the light from the light source through a second angle;

a third angle representing light that is reflected from the array as if it were a micromirrored surface,

wherein the difference between the first and third and second and third angles are substantially different.

15. A projection system, comprising:

a light source for providing a light beam;

a micromirror array comprising a plurality of micromirrors provided in a path of the light beam; and

collection optics disposed in a path of the light beam after the light beam is incident on the micromirror array and reflects off of the plurality of micromirrors as a pattern of on and off micromirrors in the array;

wherein the micromirror array comprises a substrate, the array of micromirrors being held on the substrate where each micromirror is capable of moving to an on position and an off position from a non-deflected position, wherein the on position is at a different angle than the off position relative to the non-deflected position.

16. The projection system of claim 15, wherein each micromirror is capable of pivoting to an on position that directs light to the light collection optics and capable of pivoting in an opposite direction to an off position for directing light away from the light collection optics, the micromirrors capable of pivoting to a greater extent to the on position than to the off position.

17. The projection system of claim 16, wherein each micromirror is capable of pivoting from −

1 to −

10 degrees from a rest position to the off position, and capable of pivoting greater than +10 degrees from the rest position to the on position.

18. The projection system of claim 17, wherein each micromirror is capable of pivoting from −

1 to −

11 degrees from the rest position to the off position, and capable of pivoting from +12 to +20 degrees from the rest position to the on position.

19. The projection system of claim 16, wherein the micromirrors are capable of pivoting at least three degrees further to the on position than to the off position, though in opposite directions.

20. The projection system of claim 16, wherein the collection optics is a single lens or group of lenses for all of the micromirrors in the array.

21. The projection system of claim 16, wherein the array of micromirrors are disposed in a package, the package having a light transmissive window that is at an angle to a substrate on which the micromirrors are formed.

22. The projection system of claim 21, wherein the window is at an angle of from −

2 to −

15 degrees relative to the substrate.

23. The projection system of claim 17, wherein the window is at an angle of from −

3 to −

10 degrees relative to the substrate.

24. The projection system of claim 15, wherein the array of micromirrors are disposed in a package, the package having a light transmissive window that is at an angle to a substrate on which the micromirrors are formed.

25. The projection system of claim 24, wherein the window is at an angle of from −

2 to −

15 degrees relative to the substrate.

26. The projection system of claim 17, wherein the window is at an angle of from −

3 to −

10 degrees relative to the substrate.

27. A method for projecting an image onto a target, comprising:

directing a light beam from a light source onto a micromirror array;

modulating the micromirrors each to an on or off position, wherein in the on position, micromirrors direct light to collection optics disposed for receiving light from micromirrors in their on position, wherein the pattern of on and off micromirrors forms an image; and

wherein the position of the micromirrors in their on position is at a different magnitude of an angle compared to the magnitude of the angle of the micromirrors in their off position.

28. A method for spatially modulating a light beam, comprising directing a beam of light onto an array of micromirrors, the micromirrors capable of movement to a first or second position, wherein in the first position the micromirrors direct a portion of the beam of light incident thereon into a collection optic, and wherein the minimum distance between adjacent micromirrors when each in the second position is less than the minimum distance between the adjacent micromirrors when each is in the first position.

29. The method of claim 28, wherein the minimum distance is determined in a direction non-parallel to the axis of rotation of the micromirrors.

30. The method of claim 28, wherein the distance is between adjacent parallel micromirror edges that have moved due to rotation of the micromirrors to either the first or second position, and the minimum of the distance is a closest point between the parallel edges of the adjacent micromirrors.

31. A device comprising:

a substrate on which is formed a movable reflective or diffractive micromechanical device;

a package for holding the substrate with the movable micromechanical device;

wherein the package comprises an optically transmissive window that is non-parallel to the substrate.

32. The device of claim 31, wherein the micromechanical device is a light modulator array.

33. The device of claim 31, wherein the window is at an angle of from −

2 to −

15 degrees relative to the substrate.

34. The device of claim 33, wherein the window is at an angle of from −

3 to −

10 degrees relative to the substrate.

35. The device of claim 31, wherein the optically transmissive window is display quality glass.

36. The device of claim 31, further comprising bond wires on a first side for electrically connecting the substrate to the package.

37. The device of claim 36, wherein the optically transmissive window is further from the substrate at a point above the bond wires on the substrate than at an opposite end of the substrate.

38. The device of claim 31, wherein the package is a hermetic or partially hermetic package.

39. The device of claim 38, further comprising a molecular scavenger in the package.

40. The device of claim 31, wherein the micromechanical device is a micromirror array for spatially modulating a light beam.

41. The device of claim 40 that is disposed within a projection system.

42. The device of claim 40, wherein each micromirror of the array has an on and off state, wherein the on state is at a different magnitude of an angle relative to the substrate than the off state.

43. The device of claim 42, wherein each micromirror abuts against the substrate or structure on the substrate when in the on and off states.

44. The device of claim 42, wherein the on and off positions are greater than a magnitude of 0 degrees relative to the substrate but less than 45 degrees relative to the substrate.

45. The device of claim 44, wherein the on position is from +10 to +30 degrees and the off position is less than between 0 and −

10 degrees.

46. The device of claim 45, wherein the on position is from +12 to +20 degrees and the off position is less than between 0 and −

12 degrees.

47. The device of claim 40, wherein micromirrors in the micromirror array are disposed on a semiconductor or light transmissive substrate.

48. The device of claim 47, wherein the substrate is a silicon substrate having circuitry and electrodes thereon for moving micromirrors adjacent thereto.

49. The device of claim 42, wherein the on and off positions are defined by the micromirrors abutting against a substrate or structure thereon.

50. The device of claim 42, wherein the structure thereon are landing electrodes at the same potential as the micromirrors.

51. The device of claim 42, wherein the micromirrors in the array are constructed so as to be pivotable around an axis from a non-deflected position to the on or the off states.

52. The device of claim 42, wherein the micromirrors are digitally addressed.

53. The device of claim 42, wherein the micromirrors have the shape of a concave polygon.

54. The device of claim 42, wherein non-flexible portions of the micromirrors have substantially the shape of an assembly of one or more side by side parallelograms.

55. The device of claim 40, wherein non-flexible portions of the micromirrors have substantially the shape of an assembly of one or more side by side parallelograms.

56. A projection system, comprising:

a light source;

light collection optics;

a substrate on which is formed a movable reflective or diffractive micromechanical device;

a package for holding the substrate with the movable micromechanical device;

wherein the package comprises an optically transmissive window that is non-parallel to the substrate;

the packaged micromechanical device disposed in a path of a light beam from the light source for

modulating light from the light beam, and the collection optics collecting the modulated light.

57. The projection system of claim 56, wherein the micromechanical device is a light modulator array.

58. The projection system of claim 56, wherein the window is at an angle of from −

2 to −

15 degrees relative to the substrate.

59. The projection system of claim 58, wherein the window is at an angle of from −

3 to −

10 degrees relative to the substrate.

60. The projection system of claim 56, wherein the optically transmissive window is display quality glass.

61. The projection system of claim 56, further comprising bond wires on a first side for electrically connecting the substrate to the package.

62. The projection system of claim 61, wherein the optically transmissive window is further from the substrate at a point above the bond wires on the substrate than at an opposite end of the substrate.

63. The projection system of claim 56, wherein the package is a hermetic or partially hermetic package.

64. The projection system of claim 63, further comprising a molecular scavenger in the package.

65. The projection system of claim 56, wherein the micromechanical device is a micromirror array for spatially modulating a light beam.

66. The projection system of claim 65, that is disposed within a projection system.

67. The projection system of claim 65, wherein each micromirror of the array has an on and off state, wherein the on state is at a different magnitude of an angle relative to the substrate than the off state.

68. The projection system of claim 67, wherein each micromirror abuts against the substrate or structure on the substrate when in the on and off states.

69. The projection system of claim 67, wherein movement to the on position is through an angle of greater than 0 but less than 30 degrees, and movement in the opposite direction to the off position is through an angle of between 0 and −

30 degrees.

70. The projection system of claim 69, wherein the on position is from +10 to +30 degrees and the off position is from 0 to −

10 degrees.

71. The projection system of claim 70, wherein the on position is from +12 to +20 degrees and the off position is from 0 to −

12 degrees.

72. The projection system of claim 65, wherein micromirrors in the micromirror array are disposed on a semiconductor or light transmissive substrate.

73. The projection system of claim 72, wherein the substrate is a silicon substrate having circuitry and electrodes thereon for moving micromirrors adjacent thereto.

74. The projection system of claim 67, wherein movement of the micromirrors in one direction to the on position relative to a non-deflected position is greater than 1 degree more than movement in the opposite direction of the micromirrors to the off position.

75. The projection system of claim 67, wherein the difference is more than 3 degrees.

76. The projection system of claim 67, wherein the micromirrors in the array are constructed so as to be pivotable around an axis from a non-deflected position to the on or the off states.

77. The projection system of claim 67, wherein the micromirrors are digitally addressed.

78. The projection system of claim 67, wherein the micromirrors have the shape of a concave polygon.

79. The projection system of claim 67, wherein non-flexible portions of the micromirrors have substantially the shape of an assembly of one or more side by side parallelograms.

80. The projection system of claim 65, wherein non-flexible portions of the micromirrors have substantially the shape of an assembly of one or more side by side parallelograms.

81. The projection system of claim 65, wherein the micromirrors are digitally addressed.

82. The projection system of claim 81, wherein the micromirrors achieve grayscale by pulse width modulation.

83. The projection system of claim 65, further comprising a target upon which light from the collection optics is incident.

84. The projection system of claim 65, wherein the light source is an arc lamp.

85. The projection system of claim 65, wherein the on and off positions are at angles greater than 3 degrees but less than 30 degrees from the substrate.

86. The projection system of claim 65, further comprising a screen upon which the pattern of on and off micromirrors is incident.

87. The projection system of claim 65, further comprising a color filter for providing a series of sequential colors onto the micromirror array.

88. The projection system of claim 70, further comprising a device for improving the evenness of light distribution onto the array.

89. The projection system of claim 65, wherein the collection optics is a plurality of lenses disposed so as to project the pattern of light from the micromirror array onto a target.

90. The projection system of claim 72, further comprising one or more micromirrors or lenses for directing and focusing a cone of light onto the micromirror array.

91. The projection system of claim 56 that is a front or rear projection display.

92. The projection system of claim 65, that is a mask projector for maskless patterning of a light sensitive material.

93. The projection system of claim 75, that is a projector in a photolithography system.

94. The projection system of claim 67, further comprising a target upon which an image of a pattern of on and off mirrors is incident.

95. The projection system of claim 56, wherein the micromechanical device is a micromirror array where each micromirror has substantially no micromirror edges perpendicular to the light beam from the light source.

96. A packaged MEMS device having a substrate with a micromechanical device thereon and a window in the package disposed at an angle to the substrate.

97. The projection system of claim 96, wherein the micromechanical device is a light modulator array.

98. The projection system of claim 96, wherein the window is at an angle of from −

2 to −

15 degrees relative to the substrate.

99. The projection system of claim 98, wherein the window is at an angle of from −

3 to −

10 degrees relative to the substrate.

100. The projection system of claim 96, wherein the optically transmissive window is display quality glass.

101. The projection system of claim 96, further comprising bond wires on a first side for electrically connecting the substrate to the package.

102. The projection system of claim 101, wherein the optically transmissive window is further from the substrate at a point above the bond wires on the substrate than at an opposite end of the substrate.

103. The projection system of claim 96, wherein the package is a hermetic or partially hermetic package.

104. The projection system of claim 103, further comprising a molecular scavenger in the package.

105. The projection system of claim 96, wherein the micromechanical device is a micromirror array for spatially modulating a light beam.

106. The projection system of claim 105, that is disposed within a projection system.

107. The projection system of claim 105, wherein each micromirror of the array has an on and off state, wherein the on state is at a different magnitude of an angle relative to the substrate than the off state.

108. The projection system of claim 107, wherein each micromirror abuts against the substrate or structure on the substrate when in the on and off states.

109. The projection system of claim 107, wherein the on and off positions are greater than a magnitude of 0 degrees relative to the substrate but less than 45 degrees relative to the substrate.

110. The projection system of claim 109, wherein the on position is from +10 to +30 degrees and the off position is from 0 to −

10 degrees.

111. The projection system of claim 110, wherein the on position is from +12 to +20 degrees and the off position is from 0 to −

12 degrees.

112. The projection system of claim 105, wherein micromirrors in the micromirror array are disposed on a semiconductor or light transmissive substrate.

113. The projection system of claim 112, wherein the substrate is a silicon substrate having circuitry and electrodes thereon for moving micromirrors adjacent thereto.

114. The projection system of claim 107, wherein movement of the micromirrors in one direction to the on position relative to a non-deflected position is greater than 1 degree more than movement in the opposite direction of the micromirrors to the off position.

115. The projection system of claim 107, wherein the difference is more than 3 degrees.

116. The projection system of claim 107, wherein the micromirrors in the array are constructed so as to be pivotable around an axis from a non-deflected position to the on or the off states.

117. The projection system of claim 107, wherein the micromirrors are digitally addressed.

118. The projection system of claim 107, wherein the micromirrors have the shape of a concave polygon.

119. The projection system of claim 107, wherein non-flexible portions of the micromirrors have substantially the shape of an assembly of one or more side by side parallelograms.

120. The projection system of claim 105, wherein non-flexible portions of the micromirrors have substantially the shape of an assembly of one or more side by side parallelograms.

121. The projection system of claim 105, wherein the micromirrors are digitally addressed.

122. The projection system of claim 121, wherein the micromirrors achieve grayscale by pulse width modulation.

123. A projector comprising a light source, a packaged MEMS device having a substrate with a micromechanical device thereon and a window in the package disposed at an angle to the substrate, and collection optics disposed to receive light from the light source after modulation by the packaged MEMS device.

124. A method for making a micromirror, comprising:

providing a substrate;

depositing and patterning a first sacrificial layer on the substrate;

depositing at least one hinge layer on the sacrificial layer and patterning the at least one hinge layer to define at least one flexure hinge;

depositing and patterning a second sacrificial layer;

depositing at least one mirror layer on the second sacrificial layer and patterning the at least one mirror layer to form a mirror element; and

removing the first and second sacrificial layers so as to release the micromirror.

125. The method of claim 124, wherein the substrate is a light transmissive or semiconductor substrate.

126. The method of claim 124, wherein the sacrificial layers are deposited by spin-on, sputtering or chemical vapor deposition.

127. The method of claim 126, wherein the at least one hinge layer and the at least one mirror layer are conductive layers deposited by chemical vapor deposition or sputtering.

128. An optical micromechanical device, comprising:

a substrate;

a first post on the substrate;

a flexure hinge where a proximal end of flexure hinge is on the post;

a second post attached to a distal end of the flexure hinge; and

a plate attached to the second post.

129. The device of claim 128, wherein the device is formed by micromachining.

130. The device of claim 128, wherein the plate is a reflective and conductive micromirror.

131. The device of claim 130, wherein a plurality of flexure hinges connect the plate to the substrate, via a plurality of corresponding first and second posts.

132. A mirror array comprising:

a substrate;

an array of mirrors held on said substrate, each mirror held by a hinge to said substrate;

a plurality of electrodes formed proximate to each mirror in the array for deflecting a proximate mirror to one of only two different deflection angles depending upon a voltage being applied to one of the plurality of electrodes.

133. The mirror array of claim 132, further comprising a landing electrode held at the same potential as the mirrors in the array.

134. The mirror array of claim 133, wherein a landing electrode is disposed for a mirror on position and a mirror off position.

135. The mirror array of claim 132, wherein a voltage is applied to one electrode of the plurality of electrodes for electrostatically pulling an adjacent mirror to an on position, and a voltage is applied to another electrode of the plurality of electrodes for electrostatically pulling the adjacent mirror to an off position different from the on position.

136. A package for a micromechanical device comprising a bottom substrate for holding the micromechanical device and a top light transmissive substrate that is non-parallel to the bottom substrate.

137. The package of claim 136, capable of hermetic sealing.

138. The package of claim 137 comprising a getter and an agent for reducing stiction.

139. The package of claim 136, further comprising a micromechanical device disposed on the bottom substrate.

140. The package of claim 139, wherein the non-parallel light transmissive substrate is at an angle of from −

1 to −

15 degrees relative to the bottom substrate.

141. The package of claim 140, further comprising bond wires connecting the micromechanical device to the bottom substrate.

142. The package of claim 136, further comprising a bond pad on the bottom substrate.