ANALYSIS OF H-2-DILUTION EFFECTS ON PHOTOCHEMICAL VAPOR-DEPOSITION OFSI THIN-FILMS

Hg-sensitized photochemical vapor deposition (photo-CVD) of Si thin fi lms at low temperatures using a gas mixture of SiH4 and H-2 was analyz ed and the concentrations of SiH3 and H in the gas phase were theoreti cally estimated. The results of the calculation were compared with the properties of the Si thin films; and the roles of atomic H were discu ssed. With the correlations between the radical concentrations near th e growing surface and him properties such as film structure, film qual ity, and the concentration of bonded hydrogen in a-Si films were succe ssfully explained. It is suggested thai the roles of atomic H on the g rowing surface are a termination of dangling bonds on the surface and an extraction of SiH3 radicals from the growing surface. Since the rol e of atomic H competes with the deposition of Si, the supply balance b etween the atomic H and the SiH3 radicals is essential to determine th e properties of Si thin films.