A theoretical investigation was made of the N-doping effect upon vacancy aggregation and O precipitation processes in Czochralski Si. By using first-principles calculations, stable atomic configurations and the formation energies of various complexes formed by vacancies (V), O and N were investigated. It was found that V and O formed stable complexes, but some O capture processes were endothermic; suggesting that V aggregation occurred preferentially, resulting in void growth. It was also found that the {N2–V2} complex, which was already known to be the most stable complex among N and V complexes, effectively captured several O atoms, and then formed stable {N2–V2–On} complexes. The stable {N2–V2–On} complexes could become the heterogeneous nucleation sites of O precipitates, suggesting that N doping drove the aggregation of O. This was consistent with the experimentally observed enhancement of O precipitate formation due to N doping. An experimentally observed shape change of voids was attributed to anisotropic void growth originating from the N and N–O involved in void formation during growth.

First-Principles Investigations of Nitrogen-Doping Effects on Defect Aggregation Processes in Czochralski Si. A.Taguchi, H.Kageshima, K.Wada: Journal of Applied Physics, 2005, 97[5], 053514 (5pp)