Influence of Hydrogen on the Mechanism of Permanent Passivation of Boron–Oxygen Defects in p-Type Czochralski Silicon

Strong evidence is provided for the critical role of hydrogen in the permanent passivation of boron-oxygen (B-O) defects in p-type Czochralski silicon. In particular, the impact of rapid thermal processing (firing), plasma exposure, and hydrogen-containing dielectrics on B-O defect passivation is explored. Importantly, no permanent passivation of B-O defects is observed in samples fired bare (both with and without exposure to a hydrogen-rich plasma prior to firing) and in nonfired samples coated with hydrogenated silicon nitride (SiNx:H). In contrast, samples with SiNx:H layers present during firing resulted in significant levels of B-O passivation, even at firing temperatures as low as ~500 °C. Increasing peak firing temperatures (T_peak) appeared to correlate to increased B-O passivation ability; however, increasing T_peak above a value of 670 °C resulted in suboptimal levels of surface and bulk passivation. These observations are explained within a hydrogen-based model for permanent passivation of B-O defects. Implications for nonhydrogen-based models are also discussed.