Influence of hydrogen on interstitial iron concentration in multicrystalline silicon

Abstract

The purpose of this work is to investigate the influence of in-diffusing atomic H into a multicrystalline silicon (mc-Si) wafer on the concentration of interstitial iron (Fei). Vertically adjacent wafers were annealed with and without in-diffusing H. In-diffusion was realized by exposing the samples to a microwave induced remote hydrogen plasma (MIRHP). [Fei] was detected based on lifetime measurements before and after dissociating the FeB complex. Surface passivation was achieved by a quinhydrone-methanol solution to avoid further temperature steps and indiffusion of H during passivation. From [Fei] measurements before and after the annealing steps with and without H, the influence of H alone on [Fei] could be accessed. The results were compared to experiments where SiNx:H layers were used as surface passivation for [Fei] measurements after low temperature anneals (300°C – 500°C). It could be shown that a H plasma atmosphere has a strong additional effect on the reduction of [Fei] compared to temperature effects alone. This additional reduction is proportional to the [Fei] after the annealing step alone.