Low Temperature Silicon Epitaxy Deposited by Very Low Pressure Chemical Vapor Deposition: I . Kinetics

The growth rate of low temperature (<850°C) silicon epitaxial films was studied as a function of pressure and temperature for a very low pressure (<12 mtorr) chemical vapor deposition process both with and without plasma enhancement. The data suggest that nonplasma epitaxial depositions between 750° and 850°C are rate limited by the incorporation of adatoms into the growing crystal structure. Below 700deg;C, the rate limiting step changes to one associated with the decomposition of the silicon source, silane. Plasma depositions grow at a somewhat enhanced rate due to the presence of a small but reactive population of radicals. The rate limiting step for plasma depositions seems to be related to the desorption from the wafer surface of hydrogen created by silane decomposition.