Passivation effect of SiNx:H films formed by microwave remote plasma CVD for P-diffused substrates

Hydrogenated silicon nitride (SiN_x:H) films on the P-diffused and non diffused substrates were deposited by remote plasma-enhanced chemical vapor deposition (RPECVD) to study the passivation effect on recombination lifetimes and obtain the optimized conditions for SiN_x:H deposition. The effective carrier lifetimes were strongly affected by gas ratio, temperature and deposition time conditions. The maximum effective carrier lifetimes in substrates passivated with SiN_x:H layers deposited by SiH₄/NH₃ ratio of 15/40 exceeded those of chemically passivated (CP) substrates with iodine/ethanol solution. The best thickness of SiN_x:H deposited on non-diffused wafer and the optimized thickness of P-diffused one are different, and the latter is more thicker. The reflection of SiN_x:H single layer was reduced compared with SiO₂ films and SiN_x:H/SiO₂ double layers deposited on non-diffused wafers. The effect of forming gas anneal (FGA) on the effective lifetimes at different temperature (600-800 °C) were examined. The effective lifetime increased in a short time and degraded with increasing annealing time. Fast degradation mechanism at higher annealing temperatures was observed.