Measurement and modeling of boron diffusion in Si and strained Si1−xGex epitaxial layers during rapid thermal annealing

Boron concentration profiles in rapid thermally annealed Si and strained Si1−xGex in situ doped, epitaxial layers were measured using secondary-ion-mass spectroscopy. Comparison of the Si1−xGex samples to the Si samples after rapid thermal annealing revealed a retarded B diffusivity inside the strained Si1−xGex layers. A simple empirical expression for the B retardation, which depended linearly on the Ge concentration, was developed and incorporated into a diffusion model for dopants in heterostructures. This model accurately simulated the measured B concentration profiles over a wide range of Ge fractions (0%–10%), B peak concentrations (2×1018–3×1019cm−3), and rapid thermal annealing conditions (900–1025 °C for 20–30 s).