Growth mechanism of microcrystalline and polymorphous silicon film with pure silane source gas

Microcrystalline, polymorphous and amorphous silicon films were deposited in a standard radio frequency (rf) plasma enhanced chemical vapour deposition system at a high growth rate by using pure silane as source gas. The influence of thermal gradient variation on the growth model of the hydrogenated silicon film was investigated. The structure and optical properties of these silicon samples were characterized by Raman spectroscopy, spectroscopic ellipsometry and Fourier transform infrared spectrometry. The phase state at the boundary of the deposited silicon films was analysed using ion drag and plasma-induced thermophoresis on particles in a rf glow discharge. The results showed that control of the thermal gradient allows a switch from polymorphous to microcrystalline silicon growth. The crystalline volume fraction increases with increasing film thickness, and this demonstrates that there is a crystalline gradient between the surface and the bottom of the microcrystalline silicon film.