Evaluation of anisotropic strain relaxation in strained silicon-on-insulator nanostructure by oil-immersion raman spectroscopy

Precise stress measurements have been desired in order to apply strained Si substrates to next-generation transistors. Oil-immersion Raman spectroscopy enables the evaluation of the anisotropic stress state in the strained Si layer of the strained Si substrate even under (001)-oriented Si backscattering geometry. First, we found that the phonon deformation potentials (PDPs) reported by Anastassakis et al. in 1990 was the most valid among the three sets of PDP previous reported. Using these PDPs, the precise Raman measurements of biaxial stress in strained Si-oninsulator (SSOI) nanostructures were performed. The biaxial stresses σxx and σyy decreased with the decrease in SSOI width and length, which was consistent with the finite element method calculation.