REACTION-KINETICS IN SYNCHROTRON-RADIATION-EXCITED SI EPITAXY WITH DISILANE .2. PHOTOCHEMICAL-VAPOR DEPOSITION

When a Si substrate in ambient disilane (Si2H6) is irradiated with synchrotron radiation (SR), three distinct species are excited simultaneously: irreversibly chemisorbed surface hydride, disilane gas, and disilane weakly trapped on the surface. The species-specific growth pathways in the SR-excited chemical-vapor deposition (SR-CVD) were investigated to clarify the reaction kinetics. Growth at pressure less than 10(-5) Torr is due predominantly to the regeneration of new chemisorption sites by stimulated hydrogen desorption. With increasing pressure, the role of gas-phase photolysis becomes important. In the nonirradiated region, Eley-Rideal-type reactions of the decomposition products with the surface hydrides deposit Si adlayers in a layer-by-layer fashion. In the irradiated region, however, growth resulting from multilayer photolysis of weakly trapped disilane produces a hydrogenated Si network layer on the surface, and the layer converts to a uniform and epitaxial Si film. (C) 1995 American Institute of Physics.