Strain partition of Si/SiGe and SiO2/SiGe on compliant substrates

Abstract

Strain partitioning of crystalline Si and amorphous SiO2 deposited on crystalline SiGe on a compliant viscous borophosphorosilicate (BPSG) glass has been observed. Pseudomorphic epitaxial Si was deposited on SiGe films, which were fabricated on BPSG by wafer bonding and the Smart-cut® process. The strains in SiGe and Si films were found to change identically during a high-temperature anneal which softened the BPSG film, indicating a coherent interface between SiGe and Si films and precluding slippage or the formation of misfit dislocations along the interface. The stress balance between the layers dictated the final state, which confirmed that BPSG was a perfectly compliant substrate and did not exert any force on the layers above it. Similar results were found for amorphous SiO2 deposited on SiGe on BPSG and then annealed. This shows that the viscous BPSG is an effective compliant substrate for the strain engineering of elastic films without the introduction of dislocations.