Etchant and method of use

Abstract

A method of anisotropically etching a semiconductive substrate uses a hydrofluorocarbon etch gas with an etch selectivity fluorocarbon gas. The fluorocarbon gas is used under conditions that enhance selectivity of the etch to an etch stop layer with respect to a bulk dielectric material such as doped or undoped silicon dioxide. In one method, a silicon dioxide dielectric layer is provided upon an etch stop layer, wherein the etch stop layer comprises silicon dioxide that is doped differently from the silicon dioxide dielectric layer. A gaseous etchant including a hydrofluorocarbon etch gas and a fluorocarbon selectivity compound is provided, and the silicon dioxide dielectric layer is exposed to the gaseous etchant.

1 . A method of removing silicon dioxide upon an etch stop layer, comprising: 
 providing a silicon dioxide dielectric layer upon an etch stop layer, wherein the etch stop layer comprises silicon dioxide that is doped differently from the silicon dioxide dielectric layer;    providing a gaseous etchant comprising a hydrofluorocarbon etch gas and a fluorocarbon selectivity compound; and    exposing the silicon dioxide dielectric layer to the gaseous etchant.    
   
   
       2 . The method of  claim 1 , wherein the fluorocarbon selectivity compound is selected from the group consisting of CF 4 , C 2 F 6 , C 4 F 8 , C 5 F 6 , C 5 F 8 , and combinations thereof.  
   
   
       3 . The method of  claim 1 , wherein the hydrofluorocarbon etch gas is provided in a first quantity, the fluorocarbon selectivity compound is provided in a second quantity, and the first quantity is at least twice the second quantity.  
   
   
       4 . The method of  claim 1 , further comprising etching the silicon dioxide dielectric layer in the gaseous etchant until the etch stop layer is exposed.  
   
   
       5 . The method of  claim 1 , wherein providing a gaseous etchant further comprises providing a gaseous etchant comprising about 30 parts to about 50 parts of a hydrofluorocarbon etch gas comprising CHF 3  and about less than one part to about 15 parts of a fluorocarbon selectivity compound.  
   
   
       6 . The method of  claim 1 , wherein providing a gaseous etchant further comprises providing a gaseous etchant comprising about 44 parts to about 45 parts of a hydrofluorocarbon etch gas comprising CHF 3  and about 0.5 parts to about 4 parts of a fluorocarbon selectivity compound.  
   
   
       7 . A method of removing silicon dioxide upon an etch stop layer, comprising: 
 providing a silicon dioxide dielectric layer upon an etch stop layer, wherein the etch stop layer comprises silicon dioxide that is doped differently from the silicon dioxide dielectric layer;    providing a first gaseous etchant comprising a hydrofluorocarbon etch gas;    providing a second gaseous etchant comprising a fluorocarbon selectivity compound; and    exposing the silicon dioxide dielectric layer to the first gaseous etchant and the second gaseous etchant.    
   
   
       8 . The method of  claim 7 , wherein the fluorocarbon selectivity compound of the second gaseous etchant is selected from the group consisting of CF 4 , C 2 F 6 , C 4 F 8 , C 5 F 6 , C 5 F 8 , and combinations thereof.  
   
   
       9 . The method of  claim 7 , wherein the first gaseous etchant is provided in a first quantity, the second gaseous etchant is provided in a second quantity, and the first quantity is at least twice the second quantity.  
   
   
       10 . The method of  claim 7 , further comprising etching the silicon dioxide dielectric layer in a mixture of the first gaseous etchant and the second gaseous etchant.  
   
   
       11 . The method of  claim 7 , wherein exposing the silicon dioxide dielectric layer to the first gaseous etchant and the second gaseous etchant comprises exposing the silicon dioxide dielectric layer to the first gaseous etchant and the second gaseous etchant simultaneously.  
   
   
       12 . The method of  claim 7 , wherein: 
 providing a first gaseous etchant further comprises providing a first gaseous etchant comprising about 30 parts to about 50 parts of a hydrofluorocarbon etch gas comprising CHF 3 ; and    wherein providing a second gaseous etchant further comprises providing a second gaseous etchant comprising about less than one part to about 15 parts of a fluorocarbon selectivity compound.    
   
   
       13 . The method of  claim 7 , wherein: 
 providing a first gaseous etchant further comprises providing a first gaseous etchant comprising about 44 parts to about 45 parts of a hydrofluorocarbon etch gas comprising CHF 3 ; and    wherein providing a second gaseous etchant further comprises providing a second gaseous etchant comprising about 0.5 parts to about 4 parts of a fluorocarbon selectivity compound.    
   
   
       14 . The method of  claim 7 , wherein exposing the silicon dioxide dielectric layer to the first gaseous etchant and the second gaseous etchant further comprises: 
 exposing the silicon dioxide dielectric layer to a constant supply of the first gaseous etchant; and    intermittently exposing the silicon dioxide dielectric layer to the second gaseous etchant wherein the second gaseous etchant is intermittently blended with the first gaseous etchant.    
   
   
       15 . A method of removing silicon dioxide upon an etch stop layer, comprising: 
 providing a silicon dioxide dielectric layer upon an etch stop layer, wherein the etch stop layer comprises silicon dioxide that is doped differently from the silicon dioxide dielectric layer;    providing a first gaseous etchant comprising a hydrofluorocarbon etch gas;    providing a second gaseous etchant comprising a fluorocarbon selectivity compound;    exposing the silicon dioxide dielectric layer to the first gaseous etchant; and    pulsing the second gaseous etchant into the first gaseous etchant during the exposing of the silicon dioxide dielectric layer to the first gaseous etchant to expose the silicon dioxide dielectric layer to a mixture of the first gaseous etchant and the second gaseous etchant.    
   
   
       16 . The method of  claim 15 , wherein the fluorocarbon selectivity compound of the second gaseous etchant is selected from the group consisting of CF 4 , C 2 F 6 , C 4 F 8 , C 5 F 6 , C 5 F 8 , and combinations thereof.  
   
   
       17 . The method of  claim 15 , wherein the first gaseous etchant is provided in a first quantity, the second gaseous etchant is provided in a second quantity, and the first quantity is at least twice the second quantity.  
   
   
       18 . The method of  claim 15 , further comprising etching the silicon dioxide dielectric layer in a mixture of the first gaseous etchant and the second gaseous etchant until the etch stop layer is exposed.  
   
   
       19 . The method of  claim 15 , wherein providing a first gaseous etchant further comprises providing a first gaseous etchant comprising about 30 parts to about 50 parts of a hydrofluorocarbon etch gas comprising CHF 3 .  
   
   
       20 . The method of  claim 15 , wherein providing a first gaseous etchant further comprises providing a first gaseous etchant comprising about 44 parts to about 45 parts of a hydrofluorocarbon etch gas comprising CHF 3 .  
   
   
       21 . The method of  claim 15 , wherein providing a second gaseous etchant further comprises providing a second gaseous etchant comprising about less than one part to about 15 parts of a fluorocarbon selectivity compound.  
   
   
       22 . The method of  claim 15 , wherein providing a second gaseous etchant further comprises providing a second gaseous etchant comprising about 0.5 parts to about 4 parts of a fluorocarbon selectivity compound.