Semiconductor device and fabrication process thereof

Abstract

A method of fabricating a semiconductor device includes the steps of modifying a damaged layer containing carbon and formed at a semiconductor surface by exposing the damaged layer to oxygen radicals to form a modified layer, and removing the modified layer by a wet etching process, wherein the modifying step is conducted by adding an active specie of an element that would obstruct formation of double bond between a Si atom and an oxygen atom by causing a chemical bond with Si atoms on the semiconductor surface.

1 . A method of fabricating a semiconductor device, comprising the steps of:
 forming a gate electrode over a surface of a semiconductor substrate;   depositing a film so as to cover said gate electrode and said surface of said semiconductor substrate;   etching said film to form sidewall insulation films at both sidewalls of said gate electrode by using a gas containing fluorocarbon, such that said surface of said semiconductor substrate is exposed, and said step of etching causes formation of a layer injected with carbon in said exposed surface of said semiconductor substrate; and   exposing said layer to plasma containing oxygen radicals and two or more radicals other than oxygen.   
     
     
         2 . The method as claimed in  claim 1 , wherein said surface of said semiconductor substrate contains Si atoms and wherein said damaged layer contains SiC. 
     
     
         3 . The method as claimed in  claim 1 , wherein said semiconductor substrate comprises a silicon substrate. 
     
     
         4 . The method as claimed in  claim 1 , wherein said step of etching further exposes a polysilicon surface of said gate electrode. 
     
     
         5 . The method as claimed in  claim 1 , wherein said gate electrode has a gate length of 90 nm or less. 
     
     
         6 . The method as claimed in  claim 1 , further comprising a step of etching said layer exposed to said plasma by a wet etching process. 
     
     
         7 . The method as claimed in  claim 6 , further comprising, after said wet etching process, introducing an impurity element into said semiconductor substrate by an ion implantation process. 
     
     
         8 . The method as claimed in  claim 7 , further comprising a step of forming a silicide layer on said semiconductor substrate. 
     
     
         9 . The method as claimed in  claim 6 , wherein said wet etching process is conducted such that there are formed stepped parts at respective lateral sides of said sidewall insulation films. 
     
     
         10 . The method as claimed in  claim 9 , wherein said wet etching process is conducted such that said stepped parts have a step height of 5 nm or less. 
     
     
         11 . The method as claimed in  claim 9 , wherein said wet etching process is conducted such that said stepped parts have a step height of 3 nm or less. 
     
     
         12 . The method as claimed in  claim 1 , wherein said gas containing fluorocarbon contains carbon, fluorine and hydrogen. 
     
     
         13 . The method as claimed in  claim 1 , wherein said two or more radicals other than oxygen are selected from the group consisting of nitrogen, hydrogen and halogen. 
     
     
         14 . The method as claimed in  claim 13 , wherein said halogen is fluorine. 
     
     
         15 . A method of fabricating a semiconductor device, comprising the steps of:
 depositing a film over a surface of a semiconductor substrate;   etching said film to form a contact hole by using a gas containing fluorocarbon such that said contact hole exposes said surface of said semiconductor substrate, and said step of etching causes formation of a layer injected with carbon; and   exposing said layer to plasma containing oxygen radicals and two or more radicals other than oxygen.