Aging- and thermal-annealing effects on the vibrational- and microstructural-properties of PECVD grown hydrogenated amorphous silicon carbon nitride thin films

Abstract

In this work, the hydrogenated amorphous silicon carbon nitride (a-SiCN:H) thin films were grown by PECVD from the discharge of silane (SiH4), methane (CH4) and nitrogen (N2) gases. Thereafter, the stability of the bonding and microstructural properties with respect to the effects of aging (under atmospheric environment) and thermal annealing (under low and high N2 flow-rates) were investigated by using Fourier transform infrared (FTIR) and micro Raman scattering techniques. Analyses on the as-prepared films showed that the SiH, Si-OH, CH and NH vibrational bonds were stable even through prolong aging while that of SiCN and CN bonds increased and SiN bonds decreased after aging. Meanwhile, low temperature annealing were found to improve the film structure due to the out-diffusion process of N atoms from weak SiN and CN bonds and migration of these N atoms to form strong SiN and CN bonds as well as restructuring of dangling bonds to form new SiC bonds. Additionally, the graphitic phase was more prominent in the film grown at low N2 flow-rate upon annealing, especially when annealed at low temperature. The CN bonds in the graphitic phase were found to be weak and released N atoms even when annealed at low temperature. However, high temperature annealing was shown to remove the graphitic phases in the film structure.