Very-Low-Temperature Preparation of Poly-Si Films by Plasma Chemical Vapor Deposition Using SiF4/SiH4/H2 Gases

Polycrystalline-Si (poly-Si) films have been prepared on glass substrates (Corning 7059) at a very low temperature (300°C) by conventional plasma chemical vapor deposition (plasma CVD) using SiF4/SiH4/H2 gases. The crystallinity was characterized by X-ray diffraction, reflection high-energy electron diffraction (RHEED), transmission electron microscopy (TEM) and Raman spectroscopy measurements. The effect of the SiH4 flow rate on crystallization proved to be large. The films indicated a strong <110>-preferred orientation. The crystalline fraction was estimated to be more than 80%. The average and maximum grain sizes were estimated to be 60 nm and 130 nm, respectively.