Measurement and Simulation of Boron Diffusivity in Strained Si₁ –_xGe_x Epitaxial Layers

Abstract

Diffusion of boron in compressively strained Si₁ –_xGe_x alloy layers grown by rapid pressure chemical vapor deposition has been studied as a function of the composition for 0.0006 ≤ x ≤ 0.15 and annealing temperature. The comparison of the Si₁ –_xGe_x samples to the Si samples after rapid thermal and furnace annealing revealed a retarded B diffusion inside the strained Si₁ –_xGe_x layers. The influence of the Ge content on the dopant diffusion was also measured and simulated, demonstrating that the diffusion of B was found to decrease with the Ge alloy content and annealing temperature. A simple empirical expression for the B retardation is presented and incorporated into a diffusion model for dopants in heterostructures. Good agreement between the measured and simulated diffusivity that includes the model for strain and chemical effects are obtained. By comparing with experimental values, our extracted (by using experiment and simulation) B diffusivity predicted a lower value (retardation).