Non-Destructive Quantitative Measurement Method for Normal and Shear Stresses on Single-Crystalline Silicon Structures for Reliability of Silicon-MEMS

This paper describes an experimental analysis method for evaluating surface stress distribution in single-crystalline silicon (SCS) microstructures using laser Raman spectroscope. A biaxial tensile tester designed for film specimens was employed to apply uni/biaxial stresses to SCS specimen having 270-nm-high, 4-mum-square SCS convex structures in the gauge section. As reported in Transducers 2007, two-curve fitting of Raman spectrum was useful for analyzing stress magnitude at the edge of convex structures. In this study, the partial least-square (PLS) method was adopted for the obtained Raman spectra at the convex edge in order to determine stress components as well as their magnitudes. By using the PLS method, the shear stress component was able to be measured in addition to the normal stress components. The stress magnitude in respective stress components was in very good agreement with that estimated by finite element analysis (FEA).