Measurement and simulation of boron diffusion in strained Si 1− xGe x epitaxial layers with a linearly graded germanium profile

Abstract

The diffusion of boron in compressively strained Si 1− x Ge x epitaxial layers with graded Ge profiles grown by rapid pressure chemical vapor deposition during furnace and rapid thermal annealing has been studied. Comparison of the Si 1− x Ge x samples to Si samples after furnace annealing (FA) and rapid thermal annealing (RTA) revealed a retarded B diffusion inside the strained Si 1− x Ge x layer. FA after RTA has only a marginal effect on B diffusion. The extracted B diffusivity from the present studies is very well comparable with available experimental and simulation results. A simple empirical expression for B diffusion is presented and incorporated into a diffusion model for dopants in heterostructures. Good agreement between the measured and simulated diffusivity is observed. It is argued that B diffusion in strained Si 1− x Ge x layers requires the inclusion of both trapping effect and strain in the formulation of the diffusion mechanism.