Relaxed SiGe Layers with High Ge Content by Compliant Substrate

Relaxed, high Ge content SiGe layers have been realized using stress balance on a compliant borophosphorosilicate glass (BPSG). A 30-nm fully-strained Si _0.7Ge _0.3 layer was transferred onto a 1 μm BPSG film by wafer-bonding and Smart-cut® processes, after which the continuous Si _0.7Ge _0.3 film was patterned into small islands to allow for lateral expansion. After the strain in Si _0.7Ge _0.3 islands was released by the lateral expansion resulting from the flow of the BPSG, a Si _0.4Ge _0.6 layer was commensurately deposited under compression. Upon equilibrium after an annealing, stress balance was formed between the SiGe films, resulting in a larger inplane lattice constant than that of relaxed Si _0.7Ge _0.3. With a thiner (6 nm) Si _0.7Ge _0.3 starting film, an in-plane lattice constant equivalent to fully-relaxed Si _0.45Ge _0.55 has been obtained.