Enhanced Internal Gettering of Iron in n/n⁺ Epitaxial Silicon Wafer: Effect of High Temperature Rapid Thermal Annealing in Nitrogen Ambient

Abstract

We report a strategy feasible for improving the internal gettering (IG) capability of iron (Fe) for n/n+ epitaxial silicon wafers using the heavily arsenic (As)-doped Czochralski (CZ) silicon wafers as the substrates. The n/n+ epitaxial silicon wafers were subjected to the two-step anneal of 650 °C/16 h + 1000 °C/16 h following the rapid thermal processing (RTP) at 1250 °C in argon (Ar) or nitrogen (N2) atmosphere. It is found that the prior RTP in N2 atmosphere exhibits much stronger enhancement effect on oxygen precipitation (OP) in the substrates than that in Ar atmosphere, thereby leading to a better IG capability of Fe contamination on the epitaxial wafer. In comparison with the RTP in Ar atmosphere, the one in N2 atmosphere injects not only vacancies but also nitrogen atoms of high concentration into the heavily As-doped silicon substrate. The co-action of vacancy and nitrogen leads to the enhanced OP in the substrate and therefore the better IG capability for the n/n+ epitaxial silicon wafer.