Removal of Oxygen from the Si(100) Surface in a DC Hydrogen Plasma

Abstract

This paper focuses on the removal of oxygen from a Si(100) surface by hydrogen plasma etching under high-vacuum conditions, i.e., the reaction-chamber base pressure is ≈10-7 mbar. The efficiency of oxygen removal from the Si(100) surface in the employed DC hydrogen glow discharge, with the sample at room temperature, is found to depend on the ratio of H2- and H2O partial pressures, the latter of which depends on the reaction-chamber base pressure and the amount of H2O liberated from the reaction-chamber walls by the plasma. This ratio reflects the competition between reduction of the Si surface by atomic hydrogen and reoxidation of the Si surface by residual H2O. A low-energy hydrogen ion bombardment is found to facilitate the reduction of the Si surface oxides. This process is most efficient when the sample potential is kept at 25 V below the plasma potential, i.e., when the surface is struck by 25-V protons.