Mechanics of edge effects in anisotropic thin film/substrate systems

摘要

The mechanical response of an anisotropic, elastic substrate subjected to an edge force on its surface was used to develop simple, analytical expressions of stress distributions for selected orientations of a substrate possessing cubic symmetry. The resulting stress distributions, calculated for both (001) and (011) orientations of a Si substrate, can differ by 20% from those predicted for an elastically isotropic case. Elastic anisotropy of strained films on a Si substrate, which produce variations in the film stress, leads to a 34% increase in SiGe film stress along [011] in the (011) orientation relative to the (001) orientation. Both of these effects are incorporated into a distributed-force formulation of the elastic relaxation at the edges of strained film features to model the stress distributions across SiGe features on Si.