Micromechanical and microoptomechanical structures with backside metalization

Abstract

The present invention provides a micromechanical or microoptomechanical structure produced by a process comprising defining the structure in a single-crystal silicon layer separated by an insulator layer from a substrate layer; selectively etching the single crystal silicon layer; depositing and etching a polysilicon layer on the insulator layer, with remaining polysilicon forming mechanical elements of the structure; metalizing a backside of the structure; and releasing the formed structure.

1 . A micromechanical or microoptomechanical structure produced by a process comprising: 
 defining the structure in a single-crystal silicon layer separated by an insulator layer from a substrate layer;    selectively etching the single crystal silicon layer;    depositing and etching a polysilicon layer on the insulator layer, with remaining polysilcon forming mechanical elements of the structure;    metalizing a backside of the structure; and    releasing the formed structure.    
     
     
         2 . The microstructure of  claim 1  wherein selectively etching the single crystal silicon further comprises the step photolithographically patterning and dry etching the single crystal silicon layer.  
     
     
         3 . The structure of  claim 1  wherein the insulator layer is an oxide layer.  
     
     
         4 . The structure of  claim 1  wherein metalizing the backside of the structure comprises: 
 etching the substrate layer and insulator away from a backside of the wafer until a backside of the single crystal silicon layer of the structure is exposed; and  
 depositing a coating of metal on the exposed backside of the single crystal silicon layer of the structure.  
 
     
     
         5 . The structure of  claim 4  wherein the metal is selected from the group consisting of gold, aluminum, chromium and platinum.  
     
     
         6 . A process for making a micromechanical or microoptomechanical structure in a wafer comprising a single crystal silicon layer bonded to a substrate layer by an insulator layer, the process comprising: 
 defining the structure in the single-crystal silicon layer;    selectively etching the single crystal silicon layer;    photolithographically patterning and etching the selectively etched single crystal silicon layer and the oxide layer,    depositing and patterning a polysilicon layer on the insulator layer;    metalizing a backside of the structure; and    releasing the formed structure.    
     
     
         7 . The process of  claim 6  wherein selectively etching the single crystal silicon further comprises the step photolithographically patterning and dry etching the single crystal silicon layer.  
     
     
         8 . The process of  claim 6  wherein the insulator layer is an oxide layer.  
     
     
         9 . The process of  claim 6  wherein metalizing the backside of the structure comprises: 
 etching the substrate layer and insulator away from a backside of the wafer until a backside of the single crystal silicon layer of the structure is exposed; and  
 depositing a coating of metal on the exposed backside of the single crystal silicon layer of the structure.  
 
     
     
         10 . The process of  claim 9  wherein the metal is selected from the group consisting of gold, aluminum, chromium and platinum.  
     
     
         11 . The process of  claim 6  further comprising: 
 depositing a PSG layer on the polysilicon layer;  
 patterning the PSG layer and polysilicon layer;  
 depositing a protective oxide layer prior to releasing the formed microoptical structure.