Study of hydrogen passivation in SiNx:H films using Fourier transform infrared and photoluminescence spectroscopy

Amorphous silicon nitride (a-SiNx:H) films were deposited at 300 degrees C by plasma-enhanced chemical vapour deposition. Silane/ammonia (SiH4/NH3) and silane/nitrogen (SiH4/N-2) gas compositions were used at various flow rates to study the effect of hydrogen passivation of the films using the photoluminescence (PL) spectroscopy. Fourier transform infrared (FTIR) spectroscopy was employed to derive the relative changes in the total bonded hydrogen (TBH) concentration with increasing flow rates. The composition and the refractive indices of the as-deposited films were also extracted using the bond density calculations from FTIR spectra. The calculated refractive indices of the silicon nitride films were consistent with the ellipsometry measurements. The PL spectra were observed to be free from any interference effect and this was attributed to the nitrogen related defects in all the a-SiNx:H films. The films deposited using SiH4/NH3 showed a higher PL intensity than those deposited in a SiH4/N-2 environment. A direct relation between the PL intensity and TBH content of the films was found.