300 mm Czochralski silicon wafers optimized with respect to voids with laterally homogeneous oxygen precipitation

The aim of this contribution was to investigate the impact of nitrogen doping on oxygen precipitation in wafers obtained from ingots optimized with respect to voids by advanced pulling methods. Wafers cut from these ingots contain a central OSF region and an outer perfect vacancy region. The density of grown-in oxide precipitate nuclei in the wafers was distributed radially very inhomogeneous due to the variation of the vacancy supersaturation being proportional to v/G. Two step thermal treatments with a nucleation at 780 °C for 3 h or an oxygen out-diffusion anneal at 1100 °C for 2 h both followed by 1000 °C for 16 h have shown that nitrogen doping of ingots results in a homogeneous BMD density on the whole wafer. A nitrogen concentration of at least 3×1013 cm-3 is required for the nitrogen enhanced oxygen precipitation indicating that diffusive nitrogen in the form of N2 complexes is a prerequisite for the increase of the nucleation rate. Nitrogen is incorporated into the oxide precipitates increasing the density of the precipitating phase and thus reducing strain energy.