Surface hydrogen content and passivation of silicon deposited by plasma induced chemical vapor deposition from silane and the implications for the reaction mechanism

Abstract

A systematic study of the enhanced concentration of hydrogen in the near surface layer of silicon deposited from silane by plasma induced chemical vapor deposition is presented as a function of temperature and ion bombardment of the surface during growth. The passivation effect of the chemisorbed hydrogen towards oxidation of the surface is documented, and a possible explanation is suggested in terms of a donatorlike effect of that hydrogen to underlying silicon. It is shown that the rate limiting step in the composite reaction mechanism of the deposition of high-quality silicon films is the ion bombardment induced dehydrogenation of the surface of the growing film. A critical value of substrate bias of −100 eV with respect to the floating potential at which radiation induced damage of the growing film commences is found experimentally. The corresponding ion impact energy agrees very well with Monte Carlo calculations using the TRIM code.