Growth mechanism of polycrystalline silicon films from hydrogen-diluted SiCl4 at low temperature

The growth process of polycrystalline silicon films fabricated at 200 °C by radio-frequency glow discharge plasma-enhanced chemical-vapor deposition technique from hydrogen-diluted SiCl4 has been investigated. We analyze the changes of crystallinity and crystalline grain size with the depth from the top surface of the film through studying the depth profiles of the Raman spectra. The results show that the top surface is composed of silicon nanometer crystalline grains and the clustered amorphous silicon. The component of crystalline phase increases with the increase in depth. Moreover, the film crystallization structure depends strongly on the power. On the other hand, it is almost independent of the substrate temperature and the annealing temperature. Comparing with the growth processes of polycrystalline silicon films from hydrogen-diluted SiH4, it is considered that the formation of nanometer size grains occurs in the gas phase reaction process at the initial stage of film growth, while the grain growth is largely governed by the surface reaction process where in the chlorine element plays an important role.