Analysis of H-2-dilution effects on photochemical vapor deposition of Si thin films

Hg-sensitized photochemical vapor deposition (photo-CVD) of Si thin films at low temperatures using a gas mixture of SiH4 and H-2 was analyzed and the concentrations of SiH3 and H in the gas phase were theoretically estimated. The results of the calculation were compared with the properties of the Si thin films; and the roles of atomic H were discussed. With the correlations between the radical concentrations near the growing surface and him properties such as film structure, film quality, and the concentration of bonded hydrogen in a-Si films were successfully explained. It is suggested thai the roles of atomic H on the growing surface are a termination of dangling bonds on the surface and an extraction of SiH3 radicals from the growing surface. Since the role of atomic H competes with the deposition of Si, the supply balance between the atomic H and the SiH3 radicals is essential to determine the properties of Si thin films.