Diffusion of ion-implanted phosphorus within thermally grown SiO2 in O2 ambient

Abstract

Phosphorus, implanted into thermally grown SiO2, was diffused in O2 ambient, and the phosphorus distribution was analyzed by secondary ion-mass spectrometry. A profile of the highly doped phosphorus revealed enhanced diffusion in its high-concentration region (above about 1×1019 cm−3). An empirical diffusion model, in which phosphorus diffusivity depends on local phosphorus concentration, is proposed. Numerical simulations using this model give well-matched profiles to the SIMS data, and parameters for the model are determined. The concentration-dependent diffusivity is ascribed to the formation of P=O bond in SiO2 layer, and to the resulting loosening of SiO2 network or increase of liquid phase with increasing phosphorus concentration. It was also found that the diffusivity becomes less dependent on phosphorus concentration with increasing annealing temperature.