Boron Diffusion in Si and Si1−xGex

Abstract
Boron diffusion in in-situ doped Si and strained Si1−xGex (x < 0.20) epitaxial layers, subjected to inert-ambient furnace annealing, was investigated as a function of temperature (T = 750 °C - 850 °C). Boron diffusivity parameters were extracted from SUPREM IV, a process simulation program. We observed slower B diffusion in strained Si1−xGex relative to that in Si for B concentration levels ranging from 2×1017 to 3×1019 cm−3. Using relaxed graded Si1−xGex as “substrates”, we also characterized B diffusion in relaxed Si1−xGex (x < 0.60) at T = 800 °C. We propose a reaction of mobile B atoms pairing with Ge atoms to model the slower B diffusion in both fully strained and relaxed Si1−xGex.