Semiconductor device and fabrication process thereof
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.