On the Mechanism of Defect Suppression in Nitrogen-Doped Silicon Single Crystals

摘要

Floating zone grown crystals were investigated with regard to the impact of nitrogen and oxygen doping on the density/size distribution of vacancy aggregates (voids/COP). The analysis of the experimental results is based on the recently proposed model that the suppression of vacancy and Si interstitial aggregation in silicon proceeds via N_2 + V = N_2V and N_2V + I = N_2, respectively. In presence of significant amounts of oxygen in the range of 3 - 8xl0~(17) at/cm~3, the formation of N_2 is strongly reduced by the reaction 2NO = N_2 + 2O_i. At lower temperatures, the equilibrium of the reaction shifts to the right hand side and N_2V complexes can form again. Depending on the temperature at which a sufficient N_2 concentration builds up, the aggregation temperature of vacancies and, hence, the density/size distribution of voids varies. It is shown that the experimental findings are in qualitative accordance with the predictions of the proposed model, but additional effects have to be considered for a quantitative analysis.