Lifetime Evaluation of Denuded Zone Quality and Intrinsic Gettering Effect on Heavy Metals

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Abstract
Minority carrier lifetime is used in electrical evaluation of intrinsic gettering. Lifetime in the intrinsic gettered wafer denuded zone is reduced to a third that of the starting material. No defects are observed in the wafers, even by transmission electron microscopy. This suggests the possibility that oxygen-related, undetectable residual defects exist in the denuded zone. Heavy metal contamination by reactive ion etching degrades the lifetime three figures to 1 µs by inducing surface defects. Intrinsic gettering can recover more than two figures of lifetime by suppressing the defects that are to be induced by heavy metals. The gettering ability of a defect is found to be 160–800 metal atoms depending upon defect size. The bulk defect density needed for gettering various degrees of heavy metals is determined. This technique is valid for a wide range of heavy metal atoms to 1017 cm-3.