Gettering of gold in silicon: A tool for understanding the properties of silicon interstitials

Abstract

The movement of gold in silicon is controlled by the reaction of gold with silicon interstitials, not by the intrinsic diffusion coefficient of gold. This fact is used to understand the role silicon interstitials play during gettering in silicon. An analysis of gold profiles after gettering reveals that high concentration phosphorus diffusion, argon-ion implantation, and mechanical damage of a silicon surface all act as sources of silicon interstitials. This finding is experimentally confirmed by studying the effect of an argon implanted surface layer on the diffusion of both phosphorus and antimony buried layers; only the phosphorus layer shows an enhancement, which is consistent with the injection of silicon interstitials. Studying the enhancement of the phosphorus diffusion versus temperature reveals that the phosphorus-interstitial pair has a migration energy of 1.3 eV. Under the assumption of local equilibrium between silicon interstitials and phosphorus atoms, estimates of the diffusion coefficient and equilibrium concentration of the silicon interstitial are made based on this enhanced diffusion data and the gold gettering profiles. These numbers are compared with other estimates in the literature.