Raman Spectrum Curve Fitting for Estimating Surface Stress Distribution in Single-Crystal Silicon Microstructure

This paper describes evaluation of surface stress distribution in single-crystal silicon (SCS) microstructure using laser Raman spectroscope. An in-house uniaxial tensile tester was employed to apply the uniaxial tensile stresses to SCS (001)[100] and (001)[110] film specimens with a number of microscale convex structures. A linear relationship between the applied tensile stress and Raman peak shift increment was obtained from Raman spectroscopy at a flat section of the specimen. Raman spectroscopy was also conducted to observe nonuniform stress distribution around the convex structures under uniaxial tensile loading. In observations around a convex structure, "two-curve fitting" was adopted for the asymmetric spectrum, which had been observed clearly under the tensile stresses of over 1000 MPa. The two-curve fitting was able to separate information of the top corner from that of the bottom one at the edge. The stress distribution estimated by the two peak positions was much closer to finite element analysis (FEA) results than that obtained by the one peak position.