Fabrication of a reflective spatial light modulator

Abstract

Fabrication of a reflective spatial light modulator including a micro-mirror array. In one embodiment, the micro-mirror array is fabricated from a substrate that is a single crystal material by only two main etching steps. A first etch forms cavities in a first side of the material. A second etch forms support post, a vertical hinge, and a mirror plate. Between the first and second etches, the substrate can be bonded to addressing and control circuitry.

1 . A method of fabricating a spatial light modulator, the method comprising: 
 forming cavities in a first side of a first substrate;    fabricating electrodes and addressing and control circuitry on a first side of a second substrate;    then bonding the first side of the first substrate to the first side of the second substrate; and    then forming hinges, connectors, and mirror plates on a second side of the first substrate.    
   
   
       2 . The method of  claim 1  wherein the first substrate comprises a single continuous piece of a material.  
   
   
       3 . The method of  claim 2  wherein the first substrate comprises single crystal silicon.  
   
   
       4 . The method of  claim 1  wherein the cavities define a spacer support frame extending to a predetermined depth into the first substrate.  
   
   
       5 . The method of  claim 4  wherein the spacer support frame comprises a plurality of spacer walls.  
   
   
       6 . The method of  claim 5  wherein the plurality of spacer walls form a grid-based three-dimensional structure surrounding the cavities on four sides.  
   
   
       7 . The method of  claim 4  wherein the hinges are connected to the spacer support frame.  
   
   
       8 . A method of fabricating a plurality of mirror plates of a spatial light modulator for display applications, the method comprising: 
 forming a plurality of wells in a first side of a first substrate;    fabricating addressing and control circuitry and electrodes on a second substrate;    bonding the first side of the first substrate to the second substrate; and    then processing the second side of the first substrate to release the plurality of mirror plates from the first substrate.    
   
   
       9 . The method of  claim 8  wherein the mirror plates are connected to the first substrate by hinges.  
   
   
       10 . The method of  claim 8  wherein the plurality of wells are bordered in a plane parallel to the first side of the first substrate by a plurality of spacer walls.  
   
   
       11 . The method of  claim 10  wherein the plurality of spacer walls form a two-dimensional grid pattern in the plane parallel of the first substrate.  
   
   
       12 . The method of  claim 10  wherein the spacer walls define a separation between the mirror plates of the first substrate and the electrodes on the second substrate.  
   
   
       13 . The method of  claim 8  further comprising thinning the second side of the first substrate prior to processing the second side of the first substrate.  
   
   
       14 . The method of  claim 13  further comprising depositing a reflective surface on the second side of the first substrate.  
   
   
       15 . The method of  claim 8  wherein fabricating addressing and control circuitry comprises fabricating a memory buffer, a display controller and a pulse width modulation array.  
   
   
       16 . The method of  claim 8  further comprising, prior to bonding the first side of the first substrate to the second substrate, aligning the first substrate with the second substrate so that the electrodes on the second substrate are positioned to control the deflection of mirror plates in the first substrate when the first and second substrates are bonded together.  
   
   
       17 . The method of  claim 16  wherein aligning the first substrate with the second substrate comprises aligning a pattern on the first substrate with a pattern on the second substrate.  
   
   
       18 . The method of  claim 8  wherein bonding the first side of the first substrate to the second substrate comprises using a low temperature bonding method performed at less than approximately 500 degrees Celsius.  
   
   
       19 . A method of fabricating an array of micro-mirrors for a reflective spatial light modulator, the method comprising: 
 forming an array of cavities in a first side of a first substrate;    fabricating addressing and control circuitry and an array of electrodes on a first side of a second substrate;    then bonding the first side of the first substrate to the first side of the second substrate; and    then forming the array of micro-mirrors on a second side of the first substrate, wherein the micro-mirrors in the array of micro-mirrors comprise a mirror plate and a hinge.    
   
   
       20 . The method of  claim 19  further comprising aligning the first substrate with the second substrate so that the array of electrodes are positioned to control the deflection of an associated mirror plate in the array of micro-mirrors when the first and second substrates are bonded together.  
   
   
       21 . The method of  claim 20  wherein the array of cavities provide room for the associated mirror plate in the array of micro-mirrors to deflect.  
   
   
       22 . The method of  claim 19  wherein the first substrate comprises single crystal silicon.  
   
   
       23 . The method of  claim 19  wherein boundary regions of the array of cavities form a spacer support frame extending to a predetermined depth into the first substrate.  
   
   
       24 . The method of  claim 23  wherein the boundary regions comprise a plurality of spacer walls.