Effects of addition of SiF4 during growth of nanocrystalline silicon filmsdeposited at 100 degrees C by plasma-enhanced chemical vapor deposition

Structural properties of nanocrystalline silicon (nc-Si) films, deposited a t 100 degrees C using SiF4/SiH4/H-2 by plasma-enhanced chemical vapor depos ition, were investigated by changing the SiF4 flow rate, [SiF4]. Ar a certa in law [SiF4] value (=[SiF4](s)), both the crystallinity and the gl ain siz e had minimum values. The Raman peak shifts corresponded well with a change in stress, and films with [SiF4](s) were suggested to be free from random stress in the local Si-Si networks. The photoluminescence spectra had the h ighest intensity and the highest peak energy at [SiF4](s). It was proposed that nc-Si films with high [SiF4] have microvoid-like grain boundaries with high densities of Si-F and SiH2 bonds, exhibiting an increase in crystalli nity and susceptibility to O contamination after deposition. These results were interpreted in terms of the change in the etch rates by H and F radica ls, depending on deposition temperature.