Conductive etch stop for etching a sacrificial layer

Abstract

In one embodiment, a micro device is formed by depositing a sacrificial layer over a metallic electrode, forming a moveable structure over the sacrificial layer, and then etching the sacrificial layer with a noble gas fluoride. Because the metallic electrode is comprised of a metallic material that also serves as an etch stop in the sacrificial layer etch, charge does not appreciably build up in the metallic electrode. This helps stabilize the driving characteristic of the moveable structure. In one embodiment, the moveable structure is a ribbon in a light modulator.

1 . A method of forming a micro device, the method comprising: 
 forming an isolation layer over a substrate;    forming a first metallic electrode over the isolation layer;    forming a sacrificial layer over the first metallic electrode;    forming a moveable structure over the sacrificial layer; and    etching the sacrificial layer between the moveable structure and the first metallic electrode using the first metallic electrode as an etch stop protecting the isolation layer, the etching of the sacrificial layer forming an air gap between the first metallic electrode and the moveable structure.    
   
   
       2 . The method of  claim 1  wherein the first metallic electrode comprises titanium-nitride.  
   
   
       3 . The method of  claim 1  wherein the sacrificial layer is deposited at a temperature greater than about 500° C.  
   
   
       4 . The method of  claim 1  wherein the sacrificial layer comprises amorphous silicon.  
   
   
       5 . The method of  claim 1  wherein the sacrificial layer is etched using a noble gas fluoride etchant.  
   
   
       6 . The method of  claim 1  wherein forming the moveable structure over the sacrificial layer comprises: 
 forming a ribbon material over the sacrificial layer; and    forming a second metallic electrode over the ribbon material.    
   
   
       7 . The method of  claim 6  wherein the ribbon material comprises silicon nitride.  
   
   
       8 . The method of  claim 6  wherein the metal comprises aluminum.  
   
   
       9 . The method of  claim 1  wherein the first metallic electrode is of a material that is stable at least up to about 900° C.  
   
   
       10 . The method of  claim 1  further comprising: 
 forming the first metallic electrode by depositing titanium over the substrate and exposing the titanium to an environment including ammonia.    
   
   
       11 . A method of forming a micro device, the method comprising: 
 forming an isolation layer over a substrate;    forming a bottom metallic electrode over the isolation layer;    forming a sacrificial layer over the bottom metallic electrode;    forming a resilient structure over the sacrificial layer;    forming a top metallic electrode over the resilient structure; and    etching the sacrificial layer between the resilient structure and the first metallic electrode using the first metallic electrode as an etch stop protecting the isolation layer, the etching of the sacrificial layer forming an air gap between the first metallic electrode and the resilient structure.    
   
   
       12 . The method of  claim 11  wherein the sacrificial layer is etched using a noble gas fluoride etchant.  
   
   
       13 . The method of  claim 11  wherein the sacrificial material comprises amorphous silicon.  
   
   
       14 . The method of  claim 11  wherein the bottom metallic electrode comprises titanium-nitride.  
   
   
       15 . The method of  claim 11  wherein the resilient structure is part of a ribbon light modulator.