Enhanced oxygen precipitation in neutron-irradiated nitrogen-doped Czochralski silicon crystal

Abstract

Nitrogen and vacancies were intentionally introduced into Czochralski silicon crystal by doping and neutron irradiation, respectively, to study the effect on oxygen precipitation. A series of isochronal anneals in the temperature range of 700–1150 °C revealed that vacancies showed the prominent enhancement effect on oxygen precipitation at temperatures below 1000 °C, whereas nitrogen exhibited the evident enhancement in oxygen precipitation at temperatures above 900 °C. It is suggested that the vacancies induced by neutron irradiation form VnOm (n, m≥1) complexes acting as nuclei to facilitate oxygen precipitation in silicon. However, the VnOm complexes are not stable at higher temperatures; thus, the enhancement effect of vacancies on oxygen precipitation decreases evidently as the temperature increases above 1000 °C. In addition to the formation of new nuclei based on the VnOm complexes, the growth of grown-in oxygen precipitates is also facilitated by the incorporation of high concentration vacancies in the neutron-irradiated silicon. In nitrogen-doped silicon, the enhanced oxygen precipitation at high temperatures primarily depends on nitrogen concentration rather than vacancy concentration as a result of forming stable N2V2 complexes acting as precipitate nuclei.