Oxygen Precipitation in N+ Silicon

Abstract

The advantages of oxygen precipitation in terms of intrinsic gettering to reduce oxidation induced surface defect densities and improve minority carrier generation lifetimes (τ) are well documented in the literature (1–3). Various gettering cycles to establish oxygen precipitation in n type and p type nondegenerate substrates have been developed (4–6), based on homogeneous nucleation theory. For nondegenerate silicon no differences in oxygen precipitation kinetics related to the dopant type have been reported. However, with the increasing interest in both p/p+ and n/n+ epitaxial layers for CMOS devices (7), work on the precipitation of oxygen in both p+ and n+ degenerate silicon substrates has revealed a dependence of oxygen precipitation kinetics on dopant type (8–11). In the case of p+ silicon the differences in precipitation kinetics are small when compared to p- silicon (10,11). For n+ silicon it has been reported (8–11) that the dopant concentration plays a major role and that a significant retardation of oxygen precipitation is observed. There are currently two different explanations for the difficulty encountered in producing sufficient oxygen precipitation in n+ Si. These are the failure to incorporate sufficient oxygen into the crystal during crystal growth (12) and an interaction between intrinsic point defects and the n type dopant, which influences the oxygen precipitation kinetics (8,13).