Etching method for insulating film

Abstract

A mixed gas containing at least a first fluorocarbon gas having C≧4 and a C/F ratio of 0.625 or higher, a second fluorocarbon gas having F≧4 and a C/F ratio of 0.5 or lower, an Ar gas, and an O 2 gas is used as an etching gas to etch an insulating film formed of a silicon oxide film or the like. This can improve an etching rate and a resist mask selection ratio, and in addition, prevent the formation of a contact hole in a bowing shape even when a high-aspect-ratio contact hole is formed.

What is claimed is:  
     
         1 . (amended) An insulating film etching method, 
 wherein a mixed gas containing at least a first fluorocarbon gas having C≧4 and a C/F ratio of 0.625 or higher, a second fluorocarbon gas having F≧4 and a C/F ratio of 0.5 or lower, an Ar gas, and an O 2  gas is used as an etching gas, and    wherein a ratio between flow rates of said first fluorocarbon gas and said second fluorocarbon gas (the flow rate of the first fluorocarbon gas/the flow rate of the second fluorocarbon gas) is 0.50 or higher, and a C/F ratio of said mixed gas as a whole is 0.52 or higher.    
     
     
         2 . An insulating film etching method as set forth in  claim 1 , wherein said first fluorocarbon gas is a C 5 F 8  gas or a C 4 F 6  gas.  
     
     
         3 . An insulating film etching method as set forth in  claim 2 , wherein said second fluorocarbon gas is one selected from a CF 4  gas, a C 2 F 6  gas, a C 3 F 8  gas, and a C 4 F 8  gas.  
     
     
         4 . (deleted)  
     
     
         5 . An insulating film etching method as set forth in  claim 1 , wherein said mixed gas further contains a hydrofluorocarbon gas.  
     
     
         6 . An insulating film etching method as set forth in  claim 5 , wherein said hydrofluorocarbon gas is a CH 2 F 2  gas.  
     
     
         7 . (deleted)  
     
     
         8 . An insulating film etching method as set forth in  claim 1 , wherein said insulating film is a silicon oxide film.  
     
     
         9 . An insulating film etching method as set forth in  claim 8 , wherein a silicon nitride film is exposed to an upper layer or a lower layer of said silicon oxide film.  
     
     
         10 . An insulating film etching method as set forth in  claim 9 , wherein said silicon oxide film is etched in a self-alignment contact forming step.  
     
     
         11 . (amended) An insulating film etching method, 
 wherein a mixed gas containing at least a first fluorocarbon gas having C≧4 and a C/F ratio of 0.625 or higher, a second fluorocarbon gas having F≧4 and a C/F ratio of 0.5 or lower, an Ar gas, and an O 2  gas is used as an etching gas, and    wherein a temperature of a substrate on which said insulating film is formed is 80° C. to 120° C.