Shinsuke Kashiwagi

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-¿m-square SCS convex structures in the gauge section. As reported in Transducers 2007 [1], 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).

Micro-Raman spectroscopic analysis of single crystal silicon microstructures for surface stress mapping

In this paper, an experimental analysis using a micro-Raman spectroscope for surface stress distribution in single crystal silicon (SCS) microstructures is described. Specially developed tensile test equipment applies a uniaxial tensile stress on SCS specimens with a 270 nm-high, 4 µm2 convex structures in the gauge section. Raman spectra around the convex region are measured using an ultraviolet laser with an excitation line of 363.8 nm. The shape of the Raman spectrum on the flat surface is symmetrical, whereas that around the edge of the convex is asymmetrical due to the multi-stress condition. Two-curve fitting is adopted for the asymmetric spectrum obtained at the edge, and the stress distribution estimated by the two peak positions is much closer to finite element analysis (FEA) results than that obtained by the one peak position. In partial least squares (PLS) analysis that is performed at the edge of the convex section only, explanatory variables are Raman spectral parameters, such as peak position, peak intensity, and full width at half maximum, and the response variable is the FEA stress distribution. The plane stress distributions derived from PLS analyses on each component are in good agreement with that from FEA. The combination of micro-Raman spectroscopy and tensile testing enables us to directly determine the stress components as well as stress magnitudes on SCS microstructures.

In-Situ Raman Spectroscopic Surface Stress Measurement of Single Crystal Silicon Microstructures Subjected to Uniaxial Tensile Loading

This paper describes Raman spectroscopic stress analysis of single crystal silicon (SCS) microstructures for development of reliability evaluation technique utilized for silicon-based microelectromechanical systems (MEMS). An in-house tensile tester was employed to apply a uniaxial tensile stress to the SCS specimen with a 270 nm-height, 4 mum-square SCS boss in the gauge section. Raman spectra on the boss were obtained under a constant tensile stress applied. The stress distribution obtained from two-curve fitting of Raman spectrum was in good agreement with that estimated by finite element analysis (FEA). The Raman spectroscopic stress evaluation method would be effective for nondestructive reliability testing for silicon-MEMS.