Silicon epitaxy at 650–800 °C using low-pressure chemical vapor deposition both with and without plasma enhancement

Abstract

A system and a procedure using chemical vapor deposition of silane at very low pressures (−² Torr) have been developed for depositing uniform, specular silicon epitaxial films both with and without plasma enhancement at temperatures as low as 650 °C. In situ cleaning of the substrate surface that overlaps into the deposition is the most critical aspect of the procedure. Undoped films deposited on substrates heavily doped with antimony or boron have abrupt doping profiles. Preliminary measurements indicate that the hole mobility of epitaxial films obtained with this process is 90% of that in bulk silicon. Films oxidized and decorated with a Secco etch show twice as many defects as a similarly treated substrate. Nonplasma growth kinetics are sensitive to surface conditions such as crystallographic orientation, and surface diffusion of adsorbed species appears to be the rate‐limiting step for depositing epitaxial films above 700 °C. Around 650 °C, the growth mechanism appears to change, possibly due to the increased presence of hydrogen on the surface. Finally, plasma enhances the growth rate, and plasma kinetics do not seem to be sensitive to surface conditions.