H-2 CLEANING OF SILICON-WAFERS BEFORE LOW-TEMPERATURE EPITAXIAL-GROWTH BY ULTRAHIGH VACUUM CHEMICAL VAPOR-DEPOSITION/

High-pressure H-2 cleaning is proposed for precleaning wafers used in low-temperature silicon epitaxial growth to remove such contaminants a s oxygen and carbon at the interface between the epitaxial layer and t he substrate in ultrahigh-vacuum/chemical vapor deposition. Increasing the H-2 partial pressure up to 1300 Pa during H-2 cleaning at 850 deg rees C was found to produce a smooth surface with the contaminants per fectly removed. To investigate the effects of roughness and contaminan ts in the wafer surface on the crystallinity of the epitaxial layer, p -n diodes were fabricated in the epitaxial layer and their characteris tics were measured. Annealing at an H-2 partial. pressure of 120 Pa pr oduced roughness and contaminants in the wafer surface causing a leaka ge current. Annealing at 1300 Pa produced smooth clean surfaces and no leakage current was observed. These results suggest that the electron ic properties of epitaxial layers are influenced by contaminants and r oughness in the wafer surface. High pressure H-2 cleaning reduces roug hness and removes contaminants in the surface, resulting in good elect ronic properties in the epitaxial layer.