Patent ID: 7611995

Claim:
A method of removing silicon dioxide films from a surface of a workpiece having a natural oxide film thereon, said method comprising: removing the natural oxide film from the surface of the workpiece by a chemical process; forming a chemical oxide film on the surface as a protective film after removal of the natural oxide film, the chemical oxide film being a silicon dioxide film formed by a chemical process using a solution prepared by mixing H 2 O 2 and NH 4 OH; and removing the chemical oxide film from the surface of the workpiece, under conditions that: a mixed gas containing HF gas and NH 3 gas is used; a processing temperature for achieving etch selectivity for the chemical oxide film to silicon is in the range of 200° C. to 400° C.; a processing pressure at which the workpiece is processed is in the range of 26 Pa (0.2 Torr) to 53,200 Pa (400 Torr); and the flow rate ratio of HF gas to NH 3 gas is in the range of 10:1 to 1:50.