Fundamental properties of intrinsic gettering of iron in a silicon wafer

Properties of intrinsic gettering of Fe were studied by measuring Fe-B complex concentration and interstitial Fe concentration in a denuded zone after isochronal or isothermal annealing followed by quenching using deep level transient spectroscopy. We calculated the Fe concentration as the Fe-B complex concentration plus the interstitial Fe concentration. Silicon wafers were contaminated with a surface Fe concentration of 4.2×1011 to 3.2×1013 cm−2 to show the relation between Fe concentration in the wafer and the temperature at which gettering occurs. Supersaturation of Fe impurities was found necessary for intrinsic gettering of Fe in the contamination range of 4.0×1012 to 3.5×1014 cm−3. Therefore, the gettering temperature is lower for low-level Fe contamination than for high-level contamination. The reduction of Fe concentration saturated with annealing time, which shows that the oxygen precipitates in the bulk defect region do not work as an infinite gettering sink. We found that the saturated Fe concentration follows a simple Arrhenius relationship, so that gettering stops at the thermal equilibrium concentration. We think that in intrinsic gettering, Fe precipitates preferentially in the bulk defect region when the Fe impurities supersaturate with decreasing temperature.