Enhanced internal gettering in n/n+ epitaxial silicon wafer: coaction of nitrogen impurity and vacancy on oxygen precipitation in substrate

Abstract

The effects of the prior rapid thermal processing (RTP) at 1,250 °C in argon (Ar) and nitrogen (N2) atmosphere on oxygen precipitation (OP) and associated internal gettering (IG) in the heavily arsenic (As)-doped Czochralski (CZ) silicon substrates of n/n+ epitaxial silicon wafers have been comparatively investigated. It is found that OP in the heavily As-doped silicon subjected to the two-step anneal of 650 °C/16 h + 1,000 °C/16 h can be significantly enhanced by the prior RTP in either Ar or N2 atmosphere. By comparison, the prior RTP in N2 atmosphere exhibits much stronger enhancement effect on OP thus leading to a better IG capability of the epitaxial wafer. Secondary ion mass spectroscopy measurement reveals that nitrogen atoms of high concentration are injected into the heavily As-doped silicon substrate by the RTP at 1,250 °C in N2 atmosphere. It is believed that the vacancy- and nitrogen-assisted heterogeneous nucleation mechanisms are simultaneously operative for OP in the substrate subjected to the prior RTP in N2 atmosphere, thus leading to the more pronounced OP and therefore the better IG capability. It is expected that the present work offers a strategy feasible for improving the IG capability of n/n+ epitaxial silicon wafers.