Interdiffusion Behavior of Si/Si1-xGex Layers in Inert and Oxidizing Ambients

Interdiffusion of Si/Si0.85Ge0.15 heterojunctions subjected to annealing in inert and oxidizing ambients was investigated as a function of temperature (900 to 1200 °C) and time, allowing comparison between intrinsic diffusion and diffusion under interstitial injection. The Ge diffusivity was extracted using the process simulation program FLOOPS. A time-independent diffusivity was observed for all temperatures. The calculated Ge diffusivity in oxidizing ambient was comparable to that in inert ambient indicating that the interstitial concentration plays a minimal role in interdiffusion. A fractional interstitial component, f1, equal to 0.10 is estimated for annealing temperatures in the range 900 to 1100 °C, while f1 increases to approximately 0.17 at 1200 °C. This may indicate a change in diffusion mechanism at a temperature greater than 1100 °C.