Segregation and diffusion of phosphorus from doped Si1−xGex films into silicon

Abstract

Segregation and diffusion of P from in situ doped Si1−xGex (0.25⩽x⩽0.8) epitaxial films into Si at 750–850 °C were investigated using secondary ion mass spectroscopy and differential resistance measurements. It was found that the surface P concentration in the diffused layer in Si was higher than the P concentration in the Si1−xGex film, which signifies the segregation of P from the Si1−xGex film into Si. The segregation coefficient, defined as the ratio of the active P concentration in the Si to that in the Si1−xGex film, was about 2.5 at 800 °C in the case of the Si0.75Ge0.25 film as a diffusion source and increased with increasing Ge fraction. It was found that the P diffusion profiles in Si were normalized by x/t, even though the segregation of P occurred, the diffusion coefficient of P depended on the surface P concentration, and the high concentration diffusion characteristics of P in Si were similar to those reported by using a conventional diffusion source.