Theoretical study of nitrogen-doping effects on void formation processe in silicon crystal growth

摘要

Nitrogen-doping effects in silicon crystal growth have been theoretically studied using thermodynamical simulation based on first-principles calculation results. The results show that the densities of various complexes are determined in the balance between the enthalpy effects and the entropy effects. They also show that about one order larger density of doped nitrogen is required in Czochralski silicon to obtain a void suppression effect similar to that in float-zone silicon. This is because oxygen itself has a weak void suppression effect due to the formation of vacancy-oxygen complexes around the void formation temperature. Competition between nitrogen and oxygen in trapping vacancies around the void formation temperature weakens the nitrogen-doping effect to suppress the void formation in Czochralski silicon. Since doped nitrogen preferentially forms nitrogen-vacancy-oxygen complexes at lower temperatures, the high density nitrogen doping enhances the oxygen precipitate density in Czochralski silicon.