Effectiveness of Embedded-SiGe in Strained-SOI Substrates and Implications on Embedded-SiGe Stress Transfer Mechanics

Embedded-SiGe is shown to be fully compatible with strained-SOI substrates. Despite a lack of lateral lattice mismatch between the SiGe and strained-SOI, the resulting drive current improvement from embedded-SiGe is identical for strained-SOI and standard SOI control (where a lateral lattice mismatch is present). This result isolates the vertical lattice mismatch as the source of stress generation from embedded-SiGe. The concept of a critical length of SiGe beyond the vertical Si-SiGe interface is introduced to explain the observed experimental results, and is confirmed by various SiGe epitaxial fill-height and stress relaxation experiments.