Analysis of the Nucleation Kinetics of Oxide Precipitates in Czochralski Silicon

Abstract

Vacancy dependent nucleation curves were measured. They exhibit four maxima which all increase with increasing vacancy concentration. Even at 1000 {degree sign}C considerable nucleation takes place for high vacancy concentrations. The analysis of nucleation based on classical nucleation theory has shown that nucleation of oxide precipitates takes place at heterogeneous nucleation sites. These sites contain oxygen atoms and vacancies and it is assumed that these sites are VOn complexes with 2<n<6. They are stable between 450{degree sign}C and 700{degree sign}C. As-grown silicon wafers contain a certain concentration of nucleation sites. This concentration increases or decreases during prolonged annealing and, as a result, the nucleation rate increases or decreases with annealing time, respectively. The grown-in concentration of nucleation sites can be markedly increased by appropriate rapid thermal anneal (RTA) pre-treatments. Supersaturated vacancies are assumed to be stored during RTA cooling mainly by reactions of vacancies with oxygen monomers, dimers, and trimers.