Phosphorus diffusion from doped polysilicon through ultra-thin SiO2 films into Si substrates

The diffusion of phosphorus into ultra-thin oxides from phosphorus-doped polysilicon sources was studied. The two-boundary diffusion model can be applied to the diffusion of phosphorus in ultra-thin oxides, and the diffusivity and segregation coefficient were obtained based on the model. The dependence of the diffusivity on oxide thickness and drive-in ambients was investigated. The enhanced diffusion, which has been observed for boron diffusion in ultra-thin oxides, was not observed for phosphorus diffusion. For the diffusion in dry O2 and wet O2 ambients, the enhanced diffusion due to high phosphorus concentration in the polysilicon was observed.