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

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.