Methods for Depositing, Releasing and Packaging Micro-Electromechanical Devices on Wafer Substrates
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 and/or 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.
1 - 105 . (canceled)
106 . A method for making a micromirror array, comprising:
providing a first wafer;
providing a second wafer;
forming circuitry and a plurality of electrodes on the first wafer to form a circuitry and electrode array;
forming a plurality of deflectable micromirror elements on either the first or second wafer to form a micromirror array;
before or after forming the plurality of deflectable micromirror elements and circuitry and electrode array, forming a trench or cavity proximate to the micromirror array and/or circuitry and electrode array;
depositing a stiction reducing agent and/or a getter into the trench or cavity;
aligning the first and second wafers;
bonding the first and second wafers together to form a wafer assembly; and
separating the wafer assembly into individual wafer assembly dies.
107 . The method of claim 106 , wherein a stiction reducing agent is deposited into a trench or cavity of one wafer and a getter is deposited into a trench or cavity of the other wafer.
108 . The method of claim 107 , wherein the stiction reducing agent is applied in liquid or solid form into the trench or cavity.
109 . The method of claim 106 , wherein a getter is deposited into the trench or cavity of one or both wafers before bonding the two wafers together.
110 . The method of claim 109 , wherein the getter is a molecular, hydrogen and/or particle getter.
111 . The method of claim 110 , wherein the getter is a particulate and moisture getter.
112 . The method of claim 110 , wherein the getter is capable of absorbing moisture.
113 . The method of claim 107 , wherein the stiction reducing agent comprises carbon and fluorine.
114 . The method of claim 106 , wherein a getter is deposited into the trench or cavity and a stiction reducing agent is applied in vapor phase to cover the micromirror array.
115 . The method of claim 114 , wherein vapor phase stiction reducing agent is a fluorinated silane.
116 . The method of claim 115 , wherein the fluorinated silane has an alkyl chain of at least 8 carbons.
117 . The method of claim 106 , wherein the first and second wafers are bonded at subatmospheric pressure.
118 . The method of claim 117 , wherein the individual wafer assembly.
119 . The method of claim 106 , wherein one of the wafers is a glass or quartz wafer having one or more rectangular masks thereon.
120 . The method of claim 119 , wherein one of the wafers comprises an array of micromirrors and the other of the wafers is transmissive to visible light.
121 . The method of claim 120 , wherein the wafer transmissive to visible light comprises one or more visible light blocking areas.
122 . The method of claim 121 , wherein the visible light blocking areas are substantially rectangular.
123 . The method of claim 106 , wherein when the wafer assembly is singulated into wafer assembly dies, a light blocking mask is disposed on a second wafer portion within each wafer assembly die.
124 . A method for making a MEMS device, comprising:
forming a plurality of MEMS elements on a first wafer;
providing a second wafer;
hermetically bonding and sealing the first and second wafers together as a substrate assembly; and
singulating the hermetic substrate assembly into multiple hermetically sealed substrate assembly dies, each comprising a MEMS element.
125 . The method of claim 124 , wherein the MEMS elements are micromirrors.
126 . The method of claim 125 , wherein each substrate assembly die comprises an array of micromirrors.
127 . The method of claim 126 , wherein the first wafer is a glass or quartz wafer.
128 . The method of claim 124 , wherein circuitry and a plurality of electrodes are formed on the second wafer prior to bonding.
129 . The method of claim 128 , wherein the second substrate is a silicon substrate.
130 . The method of claim 124 , further comprising
bonding a substrate assembly die onto a third substrate that does not fully encapsulate the substrate assembly to form an exposed and packaged substrate assembly.
131 . The method of claim 130 , further comprising wire bonding the substrate assembly die to the third substrate.
132 . The method of claim 130 , further comprising connecting the packaged substrate assembly die into a projection system.
133 . The method of claim 124 , wherein the hermetically bonding and sealing is performed at a pressure lower than atmospheric pressure.
134 . The method of claim 124 , wherein the bonding of the first wafer to the second wafer is by adhesive bonding, anodic bonding, eutectic bonding, glass frit bonding and/or solder bonding.
135 . The method of claim 134 , wherein at least two types of bonding are used to heremetically bond and seal the first and second wafers together.
136 . The method of claim 124 , wherein a trench is formed in the first or second wafer proximate to the MEMS elements formed or to be formed.
137 . The method of claim 133 , wherein the hermetically sealed substrate assembly dies comprise micromirror elements in a surrounding gas less than atmospheric pressure.
138 . The method of claim 124 , wherein the hermetic bonding and sealing is performed in an atmosphere different than air.
139 . The method of claim 138 , wherein the hermetic bonding and sealing is performed in an atmosphere that comprises an inert gas.
140 . The method of claim 139 , wherein the inert gas comprises nitrogen, argon or helium.
141 . The method of claim 124 , further comprising providing an anti-stiction material in vapor phase to the MEMS elements prior to hermetically bonding and sealing the wafers together.
142 . The method of claim 124 , wherein the anti-stiction material is formed from a silane precursor.
143 - 199 . (canceled)