Effect of radio frequency power and total mass-flow rate on the properties of microcrystalline silicon films prepared by helium-diluted-silane glow discharge

摘要

Hydrogenated microcrystalline silicon thin films have been prepared by plasma-enhanced chemical vapor deposition at relatively low deposition temperatures (180 ℃). Helium dilution of silane, instead of the more commonly approach of hydrogen dilution, has been used to promote microcrystalline growth. The effect of the applied radio frequency power (RFP) and the total gas flow on the structural, optical and electrical characteristics have been studied. As observed from the structural measurements, microcrystalline growth is favored as the applied RFP is increased and/or the total gas flow is decreased. Increasing the RFP however, brings associated an increase in the defect density in the amorphous tissue surrounding the crystalline grains and/or an increase in intra-grain defects as deduced from the structural, optical and electrical measurements. Microcrystalline growth and defect formation is rationalize in terms of the He~* deexcitation process and high energy He~+ ions bombardment.