Effect of oxygen on the diffusion of nitrogen implanted in silicon

Nitrogen implants were performed in Si wafers of variable purity, i.e., epitaxial layers, float zone, and Czochralski silicon (CZ-Si). The diffusion behavior of nitrogen reported by Hockett in Appl. Phys. Lett., 54, 1793 (1989), where nitrogen diffuses for several micrometers at temperatures as low as 750°C and the profiles assume a "double-peak" structure, is peculiar of CZ-S i. In contrast, in pure epitaxial-Si, nitrogen is immobile at low temperature but, at a higher temperature (850°C), the broadening of the nitrogen profile never assumes the shape observed in CZ-Si. Our results suggest that oxygen determines the shape of the nitrogen diffusion profiles.