In-Plane Poisson's Ratio Measurement Method for Thin Film Materials by On-Chip Bending Test with Optical Interference Image Analysis

This paper describes a simple evaluation method for in-plane Poisson's ratio of thin film materials. We designed an on-chip bending test chip that produces bending of film specimen via torsion bars, when applying normal load to loading levers. Using micro machining technologies, the test chip has been fabricated from SOI wafer. The profile of bent specimen obtained by using optical interference method enabled us to measure in-plane Poisson's ratio of the material. Average measurement value of in-plane Poisson's ratio was 0.079, which deviates by 10% from the anisotropic, finite element analysis of the test chip. The measured value includes approximately 23% error as compared to ideal value for (001)[110] single-crystal silicon (SCS). This is probably caused by strong anisotropy in the material.