Influence of hydrogen on interstitial iron concentration in multicrystalline silicon during annealing steps

Abstract

The influence of in-diffusing atomic H into an annealed multicrystalline silicon (mc-Si) wafer on the concentration of interstitial iron [Fei] was investigated. Neighboring wafers with similar initial [Fei] were annealed with and without in-diffusing H. In-diffusion was realized by exposing the samples to a microwave induced remote hydrogen plasma at 400 °C. [Fei] was detected based on lifetime measurements before and after dissociating the FeB complex. Surface passivation was achieved by a quinhydrone-methanol solution at room temperature to avoid further temperature steps or in-diffusion of H during surface 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 previous experiments where the same SiNx:H layers were used as surface passivation for multiple [Fei] measurements of mc-Si samples before and after several anneals at 400 °C. It could be shown that a H plasma atmosphere has a strong additional effect on the reduction of [Fe i] compared to temperature effects alone. A formation of H-Fe i complexes associated with the passivation of the electrical activity of Fei could be shown to be improbable because no depassivation of Fei could be observed in subsequent annealing steps at 400 °C. © 2013 American Institute of Physics.