Back surface field-induced gettering in multicrystalline silicon

The optimization of the gettering efficiency of back surface field (BSF) obtained by molecular ion implantation or doped silica-film deposition is addressed. It is found that the activation of metallic impurities co-implanted or present in the solution can limit the efficiency of the gettering in the case of rapid thermal annealing (RTA) due to the quenching inherent in fast cooling >or=80 degrees C/s. However, after classical furnace annealing with a slower cooling rate (<0.1 degrees C/s), effective gettering can occur as the impurities are mostly in a precipitated inactive form, so that the improvement level of the classical POCl/sub 3/ diffusion can be reached after boron or aluminum doped silica-film deposition or BF/sub 3/ ion implantation.<
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