Influence of gas pressure on low-temperature preparation and film properties of nanocrystalline 3C-SiC thin films by HW-CVD using SiH_4/CH_4/H_2 system

摘要

We investigated an influence of gas pressure on low-temperature preparation of nanocrystalline cubic silicon carbide (nc-3C-SiC) films by hotwire chemical vapour deposition (HW-CVD) using SiH_4/CH_4/H_2 system. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectra revealed that the films prepared below 1.5 Torr were Si-nanocrystallite-embedded hydrogenated amorphous SiC. On the other hand, nc-3C-SiC films were successfully prepared at gas pressure above 2 Torr. The high gas pressure plays two important roles in low-temperature preparation of nc-3C-SiC films: (1) leading to sufficient decomposition of CH_4 molecules through a gas phase reaction and an increase in the incorporation of carbon atoms into film and (2) promoting a creation of H radicals on the heated filament, allowing the sufficient coverage of growing film surface and a selective etching of amorphous network structure and/or crystalline-Si phase. It was found that total gas pressure is a key parameter for low-temperature preparation of nc-3C-SiC films.