Deposition and Characterization of Polycrystalline Silicon Thin-Films by Reactive Thermal Chemical Vapour Deposition at 450°C

摘要

We have investigated the optimal conditions for the growth of high quality polycrystalline silicon thin films by newly developed thermal chemical vapor deposition technique, i.e., reactive thermal chemical vapor deposition that features disilane and fluorine as source gases. We found that the residence time plays a key role for the deposition of high quality polycrystalline silicon films directly on glass substrate at 450°C and obtained polycrystalline silicon thin films with a high crystalline volume faction of 89% at a deposition rate of 4.2nm/min, when the residence time was set for a specific time, e.g., 31s at the present condition. In addition, the high crystallinity was well established even at the early stage of film growth. We found that polycrystalline silicon film growth is subject to the thermal chemical vapor deposition mode basically except for the low-temperature crystal growth as low as 450°C. The as-deposited films exhibited a high defects density of 10~(18) cm~(-3) or more, but it was reduced by hydrogen passivation, resulting in the intrinsic properties of polycrystalline silicon thin films, i.e., conductivity of 10~(-5)-10~(-6)S/cm and its activation energy of 0.53eV.