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Hydrogénation effect on low temperature internal gettering in multicrystalline silicon

We have performed a comprehensive study into low temperature (≤ 500 °C) internal gettering in multicrystalline silicon (mc-Si). Two groups of as-grown mc-Si wafers from different ingot height positions were subjected to the same thermal treatments with surface passivation by either silicon nitride (SiNx:H) or a temporary iodine-ethanol (I-E) chemical solution. With either passivation scheme, lifetime in the relatively low lifetime samples from the bottom of the ingot improves substantially. There are however key passivation-dependent differences in behavior in other parts of the ingot. Lifetime in relatively good wafers from the middle of the ingot is improved significantly with silicon nitride passivation but not with iodine-ethanol, for which substantial reductions in lifetime initially occur. There are also key differences in the internal gettering behavior of bulk iron. We suggest the differences arise because silicon nitride introduces hydrogen into the bulk, whereas the iodine-ethanol does not.