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

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 (N-2) 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 N-2 flow-rates) were investigated by using Fourier transform infrared (FTIR) and micro Raman scattering techniques. Analyses on the as prepared films showed that the Si-H, Si-OH, C-H and N-H vibrational bonds were stable even through prolong aging while that of Si-C-N and C-N bonds increased and Si N 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 Si-N and C-N bonds and migration of these N atoms to form strong Si-N and C-N bonds as well as restructuring of dangling bonds to form new Si-C bonds. Additionally, the graphitic phase was more prominent in the film grown at low N-2 flow-rate upon annealing, especially when annealed at low temperature. The C-N 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. (C) 2017 Elsevier B.V. All rights reserved.