Residual stress analysis in Si-based multilayer structure by micro-Raman spectroscopy

Si-based multilayer structures, such as porous silicon (PS) and strained silicon (ε-Si), are widely used in current microelectronics and Micro-electromechanical Systems (MEMS). During the preparing process of the Si-based multilayer film, some inhomogeneous residual stress is induced, resulting of the competition between interface mismatching, surface energy and finally leading to structure failure. Micro-Raman Spectroscopy (MRS) is regarded as an effective method of intrinsic stress measurement. This work presents a methodological study on the Raman-mechanical measurement. MRS is applied to analysis the residual stress distribution along the cross section of Si-based multilayer structure. Raman experimental results show that there exists noticeable residual stress in both silicon substrate and the films (including porous silicon film and silicon germanium buffer layer). The residual stress is linearly varied in most regions, which leads to an overall warp of the structure. While nonlinear variation of residual stress appears at the interface between different films and Si-substrate. Based on the experimental results, a spectra-mechanical model for analyzing the transversely-isotropic material like porous silicon was presented. A set of detailed Raman stress relationship of porous silicon was achieved. For the study of strained silicon wafer, an analysis procedure of the residual stress evaluation on multilayer semiconductor structures was introduced.