Lifetime Engineering by Oxygen Precipitation in Silicon

This work studies the preannealing steps 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, we get the following conclusions: 1) LO-HI pretreatments produce an increase of defects with respect to non-preannealed wafers; such an increase is not observed in HI-LO pretreatments; 2) for HI-LO preanneals an optimum high temperature treatment can be found, which gives lower amount of defects 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.