Method for smoothing surface of silicon single crystal substrate

摘要

A method for microscopically smoothing a surface of a wafer made of silicon single crystal having a low resistivity. In the method, a native oxide film grown on a surface of a wafer having polished by an ordinary mirror polishing process is removed at a temperature of less than 100 DEG C. with use of a mixture gas of HF and H2, and then an organic substance deposited thereon is removed at a temperature of less than 800 DEG C. with use of a mixture gas of HCl and H2. Re-growth of an oxide film is suppressed in a consistent H2 atmosphere, during which the wafer is substantially not varied in its surface roughness. Then the wafer is thermally treated in an H2 gas atmosphere at a temperature of not less than 800 DEG C. and less than 1000 DEG C. A process of etching the silicon single crystal substrate and a process of depositing silicon atoms caused by decomposition of a silane compound generated are competitively carried out to thereby soften the microscopic rough surface of the wafer and to improve a smoothness over the smoothness of the mirror-polished surface. Since all process temperatures are set to be less than 1000 DEG C., vaporization of impurities in the wafer can be suppressed and its low resistivity can be secured.