Selectively etching silicon using fluorine without plasma

Abstract

A process for selectively etching silicon from a workpiece without etching silicon oxide or silicon nitride. The principal etchant gas is molecular fluorine gas (F 2 ) that is not excited to a plasma state.

1 . A process for selectively etching silicon from a workpiece without etching silicon oxide or silicon nitride, comprising the steps of: 
 mounting the workpiece within a chamber interior; and    supplying to the chamber interior a gas mixture including one or more gases while sealing the chamber interior to prevent any gas other than said gas mixture from entering the chamber interior, wherein 
 said one or more gases includes molecular fluorine, and  
 the molecular fluorine is not excited to a plasma state.  
   
     
     
         2 . A process according to  claim 1 , further comprising the step of: 
 heating the workpiece sufficiently for the molecular fluorine to react with any exposed silicon on the workpiece.    
     
     
         3 . A process according to  claim 1 , further comprising the steps of: 
 before the step of supplying the gas mixture, depositing silicon on the workpiece; and    during the step of supplying the gas mixture, elevating the temperature of the workpiece sufficiently for the molecular fluorine to react with the silicon.    
     
     
         4 . A process according to  claim 1 , wherein the gas mixture consists essentially of molecular fluorine.  
     
     
         5 . A process according to  claim 1 , wherein the gas mixture includes no substantial amount of any reactive gas other than molecular fluorine.  
     
     
         6 . A process according to  claim 1 , wherein the gas mixture includes no substantial amount of any substance that reacts with silicon oxide in the absence of a plasma.  
     
     
         7 . A process according to  claim 1 , wherein the gas mixture includes no substantial amount of any substance that reacts with silicon nitride in the absence of a plasma.