The Role of Oxygen in Silicon p–n Junction Gettering

The preannealing steps are investigated at high (HI) and low (LO) temperatures for internal gettering in medium oxygen content silicon slices [(7 ± 1.5) × 1017 oxygen atoms/cm3]. By using silicon p–n junctions as test vehicles the following conclusions are made: 1) LO–HI preanneals produce an increase of defect density with respect to non-preannealed wafers; such an increase is not observed in HI–LO preanneals; 2) for HI–LO preanneals an optimum high-temperature treatment can be found, which gives lower values of defect density with respect to non-preannealed wafers, reproducibly from lot to lot; 3) in HI–LO preannealed wafers the recombination lifetime increases with increasing the oxygen diffusion length of the high-temperature pretreatment; the electron diffusion length in the bulk decreases with increasing initial interstitial oxygen concentration; 4) oxygen precipitates are not effective getter sites for metal impurities.