The Si–Ge interdiffusivity in epitaxial strained Si/Si1−yGey/strained Si/relaxed Si1−xGex heterostructures was determined for Ge fractions of between 0 and 0.56, at 770 to 920C. Boltzmann-Matano analysis was applied to determine interdiffusivity from diffused Ge profiles in strained Si/relaxed Si1−xGex heterostructures. A model for the interdiffusivity suitable for use in the process simulator TSUPREM-4 was constructed. Si–Ge interdiffusivity increased by 2.2 times for every 10% increase in Ge fraction for interdiffusion in strained Si/relaxed Si1−xGex samples. Significantly enhanced Si–Ge interdiffusion was observed for Si1−yGey layers under biaxial compressive strain. Si–Ge interdiffusivity was found to increase by 4.4 times for every 0.42% increase in the magnitude of biaxial compressive strain in the Si1−yGey, which was equivalent to a decrease in the Ge percentage in the substrate by 10at%. These results were incorporated into an interdiffusion model that successfully predicted experimental interdiffusion in various SiGe heterostructures. For this temperature and Ge fraction range, the results could be described by:

D (cm2/s) = 3.10 x 102exp[-4.66(eV)/kT]

Threading dislocation densities of the order of 107/cm2 were had a negligible effect upon Si–Ge interdiffusion in Si/Si0.69Ge0.31 structures. Substituting the strained Si layers surrounding the Si1−yGey peak layer with SiGe layers was shown to have little effect upon the Si–Ge interdiffusivity. The implications of these findings for the design and process integration of enhanced mobility strained Si/strained SiGe metal-oxide-semiconductor field-effect transistors were considered.

Si–Ge Interdiffusion in Strained Si/Strained SiGe Heterostructures and Implications for Enhanced Mobility Metal-Oxide-Semiconductor Field-Effect Transistors. G.Xia, J.L.Hoyt, M.Canonico: Journal of Applied Physics, 2007, 101[4], 044901