Anisotropic diffusion of Ge induced by non-uniform strain in SiGe/Si interfaces at 700 to 850C was observed directly via medium-energy ion-scattering spectroscopy through its composition and strain profiles of atomic-layer depth resolution. For SiGe/Si interfaces with identical composition profiles but with different strain distributions, the anisotropic diffusion of Ge could be clearly correlated with the anisotropic relaxation of the non-uniform strain in the near-surface layer of several nm depth. The results suggested that atomic-scale strain control was critical to maintain abrupt SiGe/Si interfaces under thermal budget.

Strain-Induced Anisotropic Ge Diffusion in SiGe/Si Superlattices. Y.S.Lim, J.Y.Lee, H.S.Kim, D.W.Moon: Applied Physics Letters, 2002, 80[14], 2481-3