A Study of Gettering Effect of Metallic Impurities in Silicon

Abstract

Gettering effect of metallic impurities such as Cu, Fe and Au was studied by using the radioactive tracers. It was ascertained that the glass was not the only agent responsible for the glass gettering but outdiffusion and precipitation of impurities at lattice defects near the surface region had also an important effect on glass gettering. Mechanism of glass gettering varies drastically according to the kinds of impurities. That is, Cu is not found in the glasses and it is mostly gettered by outdiffusion regardless of the existence of the glasses. About a half of Fe is gettered in the glasses and the remainder is gettered by outdiffusion or precipitations at dislocations under the glasses. As to Au, gettering effect considerably depends on the atmosphere in which the slices are diffused. Boron nitride converted from boron glass during heat treatment in nitrogen atmosphere seems to be most effective in gettering Au from silicon.