A simple determination method of in-plane Poisson’s ratio for MEMS materials by means of on-chip pure bending test

This paper describes a novel and simple method for measuring in-plane Poisson´s ratio of film materials. We designed on-chip pure-bending test specimen where pure-bending deformation can be produced via torsion bar by application of normal load to loading lever. During pure-bending, the interference pattern of a family of hyperbola, corresponding to the contour lines of a film specimen in the out-of-plane direction, is observed with optical interferometer. In-plane Poisson´s ratio of a film specimen can be obtained from only the angle of asymptotes of hyperbola consisting of the interference lines, regardless of other material constants. The measured Poisson´s ratio of single crystal silicon (SCS) specimen was 0.063 on average, in close agreement within 2 % deviation from analytical value.