Interference-enhanced Raman Scattering in Strain Characterization of Ultra-thin Strained SiGe and Si Films on Insulator

Interference-enhanced Raman scattering was utilized to characterize strain in ultra-thin strained silicon-germanium (SiGe) and silicon layers on insulator. Strained SiGe and silicon films with thickness ranging from 10 to 30 nm on insulating borophosphorosilicate glass (BPSG) were formed by layer transfer techniques and/or strain manipulation via lateral expansion of strained films. The optical interference of the multiple reflections at the BPSG interfaces can substantially boost the reflectivity at the interfaces. The reflection improves Raman signal from SiGe and/or silicon films by increasing excitation intensity and Raman signal collection in the thin films. With the use of interference-enhanced Raman scattering, strain can be characterized at visible wavelengths for films as thin as 10 nm.