Influence of the SIN_x deposition temperature on the passivation quality of Al₂O₃/SIN_x stacks and the effect of blistering

In this study we investigate the influence of the hydrogen-rich silicon nitride (SiNx:H) deposition temperature by a direct PECVD (plasma-enhanced chemical vapour deposition) on the passivation quality of Al2O3/SiNx:H stacks and the effect of blister formation on FZ Si material. It is shown that the damage produced by the plasma during deposition of the SiNx coating can be reduced by decreasing the SiNx:H deposition temperature for a thin SiNx:H layer of ~30 nm. Furthermore, the optical analysis shows that the blistering of the Al2O3/SiNx:H stacks after SiNx:H deposition depends on the deposition temperature and the thickness of the SiNx:H layer in the case of a direct PECVD. Moreover, the density of blisters seems to be decreased by increasing the Al2O3 deposition temperature. An annealing step of 370°C for 40 min under atomic hydrogen atmosphere or under nitrogen atmosphere after SiNx:H deposition seems to be beneficial for the samples not showing severe blister formation (Al2O3/SiNx:H stack with a SiNx:H layer deposited by direct PECVD at 300°C or by indirect PECVD at 400°C)