Etch of silicon nitride selective to silicon and silicon dioxide useful during the formation of a semiconductor device

Abstract

A method for etching silicon nitride selective to silicon dioxide and silicon (polycrystalline silicon or monocrystalline silicon) comprises the use of oxygen along with an additional etchant of either CHF 3 or CH 2 F 2 . Flow rates, power, and pressure settings are specified.

1 . A method of forming a circuit structure comprising: 
 forming a first layer from a material selected from the group consisting of silicon and silicon dioxide over a semiconductor wafer substrate assembly;    forming a second layer comprising silicon nitride on the first layer;    placing the semiconductor wafer substrate into an etch chamber;    introducing an etchant consisting essentially of oxygen and one of CH 2 F 2  and CHF 3  into the etch chamber at a flow rate ratio of about 3:1 to etch at least a portion of the second layer, wherein the etchant etches through the second layer and stops on the first layer.    
   
   
       2 . The method of  claim 1  further comprising introducing oxygen into the chamber at a flow rate of between about 20 sccm to about 80 sccm and introducing the one of CH 2 F 2  and CHF 3  into the etch chamber at a flow rate of between about 5 sccm to about 25 sccm.  
   
   
       3 . The method of  claim 2  further comprising maintaining a pressure of between about 10 millitorr and about 60 millitorr during the introduction of the etchant.  
   
   
       4 . The method of  claim 3  further comprising sustaining a power of between about 300 watts and about 600 watts during the introduction of the etchant.  
   
   
       5 . A method of etching silicon nitride selective to at least one of silicon and silicon dioxide, comprising: 
 forming a first layer from a material selected from the group consisting of silicon and silicon dioxide over a semiconductor wafer substrate assembly;    forming a second layer comprising silicon nitride on the first layer;    placing the semiconductor wafer substrate into an etch chamber;    introducing an etchant consisting essentially of oxygen and CH 2 F 2  into the etch chamber at a flow rate ratio of about 3:1 to etch at least a portion of the second layer, wherein the etchant etches through the second layer and stops on the first layer.    
   
   
       6 . The method of  claim 5  wherein the oxygen is introduced into the chamber at a flow rate of between about 20 sccm to about 80 sccm and the CH 2 F 2  is introduced into the etch chamber at a flow rate of between about 5 sccm to about 25 sccm.  
   
   
       7 . The method of  claim 6  further comprising maintaining a pressure of between about 10 millitorr and about 60 millitorr during the introduction of the etchant.  
   
   
       8 . The method of  claim 7  further comprising sustaining a power of between about 300 watts and about 600 watts during the introduction of the etchant.