Quantitative Analysis of Stress Relaxation in Transmission Electron Microscopy Samples by Raman Spectroscopy with a High-Numerical Aperture Lens

Abstract

Transmission electron microscopy (TEM) has been used for the evaluation of strain in Si. In TEM measurements, stress relaxation is inevitable during the fabrication of TEM samples. It is important to know the extent of stress relaxation to obtain meaningful results in stress measurements by TEM. In this study, we demonstrate the quantitative analysis of stress relaxation in TEM samples using Raman spectroscopy with a high-numerical aperture (NA) oil-immersion lens. We consider that the z polarization of incident light can be accomplished using a high-NA lens, which allows us to excite the forbidden mode, i.e., the transverse optical (TO) phonon mode, in Si. We confirmed that the TO mode was surely excited in a strained Si on insulator (SSOI) substrate using a high-NA lens. Finally, stress relaxations in TEM samples of SSOI were obtained; the stress relaxations along the shorter and longer dimensions reach approximately 70 and 30%, respectively, in the TEM sample with a thickness of 240 nm (the length and depth of the TEM samples are 10 and 10 µm, respectively).