Methods for depositing, releasing and packaging micro-electromechanical devices on wafer substrates

• US 7,307,775 B2
• Filed: 06/11/2002
• Issued: 12/11/2007
• Est. Priority Date: 12/07/2000
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Huibers, Andrew G., Chiang, Steve, Duboc, Robert M., Chen, Hung Nan, Dehlinger, Dietrich, Richards, Peter W., Shi, Hongqin, Sun, Anthony, Patel, Satayadev R., Grobelny, Thomas J.
• Primary Examiner(s): Mack, Ricky
• Assistant Examiner(s): Thomas, Brandi
• Application Number:
  US10/167,361
• Publication Number:
  US 20050074919A1
• Time in Patent Office: 2,009 Days
• Field of Search: 359/290, 359/291, 359/295, 359/298, 359/223, 359/224, 359/292, 359/212, 359/267, 359/230, 353/98, 353/99, 353/84
• 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 1/00269 Bonding of solid lids or wafers to the substrate
• 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: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• 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 2924/01027 Cobalt [Co]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01039 Yttrium [Y]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/01054 : Xenon [Xe]
• CPC Class Codes: H01L 2924/01072 : Hafnium [Hf]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01076 : Osmium [Os]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• 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 2924/12036 : PN diode
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/12044 : OLED
• CPC Class Codes: H01L 2924/1461 : MEMS
• 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 MEMS device is disclosed. The spatial light modulator can have two substrates bonded together with one of the substrates comprising a micromirror array. The two substrates can be bonded at the wafer level after depositing a getter material andlor solid or liquid lubricant on one or both of the wafers. The wafers can be bonded together hermetically if desired, and the pressure between the two substrates can be below atmosphere.

Claims

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

forming a plurality of deflectable reflective elements on a first or second substrate;

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

bonding the substrate assembly onto a package substrate that does not fully encapsulate the substrate assembly to form an exposed and packaaged substrate assembly; and

wire bonding the substrate assembly to the package substrate.

2. The method of claim 1, further comprising disposing the exposed and packaged substrate assembly into a projection system.

3. The method of claim 2, wherein the reflective elements correspond to pixels in a direct-view or projection display.

4. The method of claim 3, wherein the number of reflective elements in each die is from 6,000 to about 6 million.

5. 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.

6. The method of claim 5, wherein the first substrate is glass, borosilicate, tempered glass, quartz or sapphire.

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

8. The method of claim 7, wherein the second substrate comprises GaAs or silicon.

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

10. The method of claim 9, wherein the adhesive is an epoxy.

11. The method of claim 10, wherein the epoxy comprises balls or rods of predetermined diameter.

12. The method of claim 1, wherein the substrate assembly is separated into individual dies by scribing and breaking.

13. The method of claim 1, wherein the substrate assembly is tested for abnormalities prior to separation into the individual dies.

14. The method of claim 1, further comprising providing a spacing substrate between the first and second substrates.

15. The method of claim 1, further comprising providing microfabricated spacers on one or both of the first and second substrates prior to bonding.

16. The method of claim 9, wherein the adhesive is dispensed by automated controlled liquid dispensing through a syringe.

17. The method of claim 9, wherein the adhesive is dispensed by screen, offset or roller printing.

18. The method of claim 16, wherein the syringe is moved along X-Y coordinates for dispensing.

19. The method of claim 1, wherein the aligning comprises registration of substrate fiducials on opposite substrates.

20. The method of claim 19, wherein the registration is accomplished with a video camera having lens magnification.

21. The method of claim 7, wherein the second substrate is a glass or quartz substrate.

22. The method of claim 1, wherein the bonding of the substrates comprises the dispensing of a UV or thermal cure epoxy.

23. The method of claim 22, wherein the bonding further comprises application of a force of 10 kg force or more.

24. The method of claim 1, wherein the aligning comprises aligning each deflectable element on the first substrate with at least one electrode on the second substrate.

25. The method of claim 1, wherein the separation of the substrate assembly comprises forming scribes on the first and second substrates.

26. The method of claim 25, wherein the scribes are placed in an offset relationship to each other in at least one direction.

27. The method of claim 25, wherein the separation further comprises breaking the substrate assembly along the scribe lines with a guillotine or fulcrum breaking machine.

28. The method of claim 1, wherein the separation of the substrate assembly comprises sawing partially through each substrate followed by breaking along the sawed lines.

29. The method of claim 1, wherein the sawing is done in the presence of a high-pressure jet of water.

30. The method of claim 1, wherein the bonding comprises applying a sealant near the perimeter of each array on the substrate.

31. The method of claim 30, further comprising applying a sealant around the perimeter of at least one of the substrates.

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

33. The method of claim 32, wherein the spacers have a size of from 1 to 20 microns.

34. 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, at least with any surface coating removed therefrom.

35. The method of claim 15, wherein the microfabricated spacers comprise an organic material.

36. The method of claim 32, wherein the spacers are glass or plastic spacers.

37. The method of claim 1, wherein the forming of the deflectable element comprises surface or bulk micromachining.

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

39. The method of claim 38, 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.

40. The method of claim 39, wherein a plurality of light blocking masks are formed on the second substrate.

41. The method of claim 40, wherein when the substrate assembly is singulated into substrate assembly dies, a light blocking mask is disposed on a second substrate portion within each substrate assembly die.

42. The method of claim 1, wherein the plurality of deflectable elements are formed on the second substrate.

43. The method of claim 42, wherein when the first and second 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.

44. The method of claim 1, further comprising packaging the substrate assembly dies.

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

46. 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.

47. The method of claim 1, further comprising applying a getter to one or both substrates before bonding the two substrates together into a substrate assembly.

48. The method of claim 47, wherein the getter is a molecular, hydrogen and/or particle getter.

49. The method of claim 47, wherein the getter is a particulate and moisture getter.

50. The method of claim 47, wherein the getter is capable of absorbing moisture.

51. The method of claim 46, wherein the stiction reducing agent is a silane applied to the deflectable elements.

52. The method of claim 46, wherein the stiction reducing agent is a chlorosilane.

53. The method of claim 1, further comprising aligning the substrates prior to bonding and singulating the bonded substrates into multiple bonded substrate die portions.

54. The method of claim 53, wherein the aligning of the substrates has an accuracy of 1 micron or less.

55. The method of claim 2, wherein the projection system comprises a light source, a color sequencer and projection optics.

83. The method of claim 25, wherein the scribes are placed in an offset relationship to each other in at least one direction.

84. The method of claim 25, wherein the separation further comprises breaking the substrate assembly along the scribe lines with a guillotine or fulcrum breaking machine.

56. A method for forming a micromirror array, comprising:

providing a first substrate;

providing a second substrate;

forming a plurality of micromirror elements on the first or second substrate;

bonding the first and second substrates together at subatmospheric pressure to form a substrate assembly; and

singulating the substrate assembly into individual dies, each die comprised of bonded first and second substrate portions with micromirror elements therebetween in a subatmospheric environment.

57. The method of claim 56, wherein the micromirror elements are formed by depositing structural films on a sacrificial layer and releasing to remove the sacrificial layer, where the releasing comprises providing an etchant selected from an interhalogen, a noble gas fluoride, a vapor phase acid, or a gas solvent.

58. The method of claim 57, wherein the releasing is followed by a stiction treatment.

59. The method of claim 58, wherein the stiction treatment comprises treatment with a silane.

60. The method of claim 58, wherein the stiction treatment is followed by said bonding.

61. The method of claim 60, wherein the time from releasing to bonding is less than 6 hours.

62. The method of claim 56, 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.

63. The method of claim 62, wherein the first substrate is a glass, borosilicate, tempered glass, quartz or sapphire wafer.

64. The method of claim 56, wherein the second substrate is a dielectric or semiconductor wafer.

65. The method of claim 64, wherein the second substrate comprises GaAs or silicon.

66. The method of claim 65, wherein the first and second substrates are bonded together with an adhesive.

67. The method of claim 66, wherein the adhesive is an epoxy.

68. The method of claim 67, wherein the epoxy comprises balls or rods of predetermined diameter.

69. The method of claim 66, wherein the substrate assembly is separated into individual dies by scribing and breaking.

70. The method of claim 56, wherein the substrate assembly is tested for abnormalities prior to separation into the individual dies.

71. The method of claim 56, further comprising providing a spacing substrate between the first and second substrates.

72. The method of claim 56, further comprising providing a microfabricated spacers on one or both of the first and second substrates prior to bonding.

73. The method of claim 66, wherein the adhesive is dispensed by automated controlled liquid dispensing through a syringe.

74. The method of claim 66, wherein the adhesive is dispensed by screen, offset or roller printing.

75. The method of claim 73, wherein the syringe is moved along X-Y coordinates for dispensing.

76. The method of claim 56, wherein the aligning comprises registration of substrate fiducials on opposite substrates.

77. The method of claim 76, wherein the registration is accomplished with a video camera having lens magnification.

78. The method of claim 64, wherein the first and second substrates are substantially circular in shape with a diameter of from 4 to 12 inches.

79. The method of claim 67, wherein the bonding of the substrates comprises the dispensing of a UV or thermal cure epoxy.

80. The method of claim 79, wherein the bonding further comprises application of a force of 10 kg force or more.

81. The method of claim 56, wherein the aligning comprises aligning each deflectable element on the first substrate with at least one electrode on the second substrate.

82. The method of claim 56, wherein the separation of the substrate assembly comprises forming scribes on the first and second substrates.

85. The method of claim 56, wherein the separation of the substrate assembly comprises sawing partially through each substrate followed by breaking along the sawed lines.

86. The method of claim 56, wherein the sawing is done in the presence of a high-pressure jet of water.

87. The method of claim 56, wherein the bonding comprises applying a sealant near the perimeter of each array on the substrate.

88. The method of claim 87, further comprising applying a sealant around the perimeter of at least one of the substrates.

89. The method of claim 56, wherein the bonding comprises applying an adhesive and spacers, the spacers having a size of from 1 to 100 microns.

90. The method of claim 89, wherein the spacers have a size of from 1 to 20 microns.

91. The method of claim 90, wherein the plurality of deflectable elements are reflective mirror elements and are formed on the second substrate which is a light transmissive substrate, at least with any surface coating removed therefrom.

92. The method of claim 89, wherein the microfabricated spacers comprise an organic material.

93. The method of claim 89, wherein the spacers are glass or plastic spacers.

94. The method of claim 56, wherein the micromirrors are provided in an array of from 100,000 to 10,000,000 micromirrors within the array.

95. The method of claim 56, further comprising bonding and wire bonding the substrate assembly to a package substrate that does not fully encapsulate the substrate assembly.

96. The method of claim 95, wherein the package substrate that does not fully encapsulate the substrate assembly is fixed within a projection system.

97. The method of claim 56, 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.

98. The method of claim 56, further comprising applying a getter to one or both substrates before bonding the two substrates together into a substrate assembly.

99. The method of claim 96, wherein the projection system comprises a light source, color sequencer and projection optics.

100. The method of claim 99, wherein the light source is an arc lamp.

101. The method of claim 100, wherein the color sequencer is a color wheel.

102. The method of claim 97, wherein the stiction reducing agent is a silane applied to the deflectable elements.

103. The method of claim 97, wherein the stiction reducing agent is a chlorosilane.

104. The method of claim 96, wherein a plurality of light blocking masks are formed on the second substrate.

105. The method of claim 104, wherein when the substrate assembly is singulated into substrate assembly dies, a light blocking mask is disposed on a second substrate portion within each substrate assembly die.

106. A spatial light modulator, comprising:

a first substrate comprising an array of micromirrors;

a second substrate comprising circuitry and electrodes for electrostatically actuating the micromirrors;

wherein the first and second substrates are bonded together hermetically as a substrate assembly so that the micromirrors are hermetically sealed from surrounding air.

107. The spatial light modulator of claim 106, wherein a gas different from air is within the hermetic environment between the first and second substrates.

108. The spatial light modulator of claim 107, further comprising a package substrate that does not fully encapsulate the substrate assembly to form an exposed and packaged substrate assembly.

109. The spatial light modulator of claim 108, further comprising wire bonds electrically connecting the substrate assembly to the package substrate.

110. The spatial light modulator of claim 108, wherein the package substrate is a substantially planar substrate.

111. A projection system comprising:

a light source, a color sequencer, the spatial light modulator of claim 106, and projection optics.

112. A spatial light modulator, comprising:

a first substrate comprising an array of micromirrors;

a second substrate comprising circuitry and electrodes for electrostatically actuating the micromirror;

wherein the first and second substrates are bonded together with an adhesive as a substrate assembly; and

wherein the first and second substrates are hermetically bonded together and a gas different from air is within the hermetic environment between the first and second substrates.

113. The spatial light modulator of claim 112, further comprising a package substrate that does not fully encapsulate the substrate assembly to form an exposed and packaged substrate assembly.

114. The spatial light modulator of claim 113, further comprising wire bonds electrically connecting the substrate assembly to the package substrate.

115. The spatial light modulator of claim 114, wherein the package substrate is a substantially planar substrate.

116. The spatial light modulator of claim 112, wherein the adhesive is an organic adhesive.

117. The spatial light modulator of claim 112, wherein the adhesive is an epoxy.

118. The spatial light modulator of claim 112, wherein the gap between the first and second substrates is 100 microns or less.

119. The spatial light modulator of claim 118, wherein the gap between the first and second substrates is 10 microns or less.

120. A projection system comprising:

a light source, a color sequencer, the spatial light modulator of claim 112, and projection optics.

121. A spatial light modulator, comprising:

a first substrate comprising an array of micromirrors;

a second substrate comprising circuitry and electrodes for electrostatically actuating the micromirrors;

wherein the first and second substrates are bonded together as a substrate assembly that has the micromirrors therebetween and a gas therebetween at a pressure less than 1 atmosphere.

122. The spatial light modulator of claim 121, wherein a gas different from air is within the hermetic environment between the first and second substrates.

123. The spatial light modulator of claim 121, further comprising a package substrate that does not fully encapsulate the substrate assembly to form an exposed and packaged substrate assembly.

124. The spatial light modulator of claim 123, further comprising wire bonds electrically connecting the substrate assembly to the package substrate.

125. The spatial light modulator of claim 124, wherein the package substrate is a substantially planar substrate.

126. The spatial light modulator of claim 121, wherein the pressure between the first and second substrates in the substrate assembly is less than 0.25 atm.

127. The spatial light modulator of claim 122, wherein the pressure between the first and second substrates in the substrate assembly is less than 50 Torr.

128. The spatial light modulator of claim 123, wherein the pressure between the first and second substrates in the substrate assembly is less than 10 Torr.

129. The spatial light modulator of claim 124, wherein the pressure between the first and second substrates in the substrate assembly is less than 1 Torr.

130. The spatial light modulator of claim 125, wherein the pressure between the first and second substrates in the substrate assembly is less than 100 mTorr.

131. The spatial light modulator of claim 121, wherein the gap between the first and second substrates is less than 100 microns.

132. The spatial light modulator of claim 131, wherein the gap between the first and second substrates is less than 10 microns.

133. A projection system comprising:

a light source, a color sequencer, the spatial light modulator of claim 121, and projection optics.

134. A spatial light modulator, comprising:

a first substrate comprising an array of micromirrors;

a second substrate comprising circuitry and electrodes for electrostatically actuating the micromirrors;

wherein the first and second substrates are bonded together as a substrate assembly that has the micromirrors therebetween and a solid or liquid lubricant and/or getter disposed between the first and second substrates proximate to the micromirrors.

135. The spatial light modulator of claim 134 herein a gas different from air is within the hermetic environment between the first and second substrates.

136. The spatial light modulator of claim 134 further comprising a package substrate that does not fully encapsulate the substrate assembly to form an exposed and packaged substrate assembly.

137. The spatial light modulator of claim 136, further comprising wire bonds electrically connecting the substrate assembly to the package substrate.

138. The spatial light modulator of claim 137, wherein the package substrate is a substantially planar substrate.

139. The spatial light modulator of claim 134, wherein the pressure between the first and second substrates in the substrate assembly is less than 1 atm.

140. The spatial light modulator of claim 139, wherein the pressure between the first and second substrates in the substrate assembly is less than 50 Torr.

141. The spatial light modulator of claim 140, wherein the pressure between the first and second substrates in the substrate assembly is less than 10 Torr.

142. The spatial light modulator of claim 141, wherein the pressure been the first and second substrates in the substrate assembly is less than 1 Torr.

143. The spatial light modulator of claim 142, wherein the pressure between the first and second substrates in the substrate assembly is less than 100 mTorr.

144. The spatial light modulator of claim 134, wherein the gap between the first and second substrates is less than 100 microns.

145. The spatial light modulator of claim 144, wherein the gap between the first and second substrates is less than 10 microns.

146. A projection system comprising:

a light source, a color sequencer, the spatial light modulator of claim 134, and projection optics.

147. A spatial light modulator, comprising:

a first semiconductor substrate comprising an array of micromirrors and circuitry and electrodes for electrostatically actuating the micromirrors;

a second substrate that is light transmissive;

the first and second substrates being bonded together.

148. The spatial light modulator of claim 147 herein a gas different from air is within the hermetic environment between the first and second substrates.

149. The spatial light modulator of claim 147 further comprising a package substrate that does not fully encapsulate the substrate assembly to form an exposed and packaged substrate assembly.

150. The spatial light modulator of claim 149, further comprising wire bonds electrically connecting the substrate assembly to the package substrate.

151. The spatial light modulator of claim 150, wherein the package substrate is a substantially planar substrate.

152. The spatial light modulator of claim 147, wherein the pressure between the first and second substrates in the substrate assembly is less than 1 atm.

153. The spatial light modulator of claim 152, wherein the pressure between the first and second substrates in the substrate assembly is less than 50 Torr.

154. The spatial light modulator of claim 153, wherein the pressure between the first and second substrates in the substrate assembly is less than 10 Torr.

155. The spatial light modulator of claim 154, wherein the pressure between the first and second substrates in the substrate assembly is less than 1 Torr.

156. The spatial light modulator of claim 155, wherein the pressure between the first and second substrates in the substrate assembly is less than 100 mTorr.

157. The spatial light modulator of claim 147, wherein the gap between the first and second substrates is less than 100 microns.

158. The spatial light modulator of claim 157, wherein the gap between the first and second substrates is less than 10 microns.

159. A projection system comprising:

a light source, a color sequencer, the spatial light modulator of claim 147, and projection optics.

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

forming circuitry, electrodes and micromirrors on a semiconductor substrate;

bonding a light transmissive substrate to the semiconductor substrate to form a substrate assembly;

bonding the substrate assembly onto a package substrate that does not fully encapsulate the substrate assembly to form an exposed and packaged substrate assembly;

wire bonding the substrate assembly to the package substrate; and

disposing the exposed and packaged substrate assembly into a projection system.

161. A method for making a plurality of spatial light modulators, comprising:

forming circuitry, electrodes and micromirrors on a semiconductor substrate;

bonding a light transmissive substrate to the semiconductor substrate to form a substrate assembly;

singulating the substrate assembly into individual substrate assembly portions each comprising a spatial light modulator; and

packaging the individual substrate assembly portions.