Impact of germanium co-doping on oxygen precipitation in heavily boron-doped Czochralski silicon

We have investigated the impact of germanium (Ge) co-doping on oxygen precipitation (OP) in heavily boron (B)-doped Czochralski (CZ) silicon subjected to low-high two-step anneal without or with the prior high temperature rapid thermal process (RTP). Herein, the Ge concentration is one order of magnitude higher than the B concentration. It is found that the Ge co-doping exhibits the effect of suppression or enhancement on OP in the heavily B-doped CZ silicon without or with the prior RTP. In the case without the prior RTP, the compressive stress introduced by the Ge co-doping compensates the tensile stress arising from the B-doping, which is not beneficial for the growth of oxide precipitates. While, in the case with the prior RTP, the Ge co-doping increases the amount of vacancies introduced by the RTP and, moreover, may enable to generate more heterogeneous nucleation centers of oxide precipitates, thus leading to the enhanced OP in the heavily B-doped CZ silicon.