VM-TEST: Mechanical property measurement using electrostatically actuated vertical MEMS test structures fabricated in thick metal layers

Abstract

An efficient method is presented to determine the mechanical properties of thick metal layers using the pull-in voltage of electrostatically actuated structures. To fabricate these high aspect ratio beams without severe deformations, additional features were added, which made existing pull-in voltage equations inaccurate and therefore corrections were necessary. ANSYS Multiphysics was used to analyze the differences between ideal beams and the fabricated beams. To demonstrate the proposed approach, both nickel and gold devices were fabricated. To extract the material property values, a sum of least squares fitting scheme was used. A Young’s modulus of 186.2 and 60.8 GPa was obtained for nickel and gold structures respectively. Both values are significantly smaller than values reported for bulk material, but fall within the range of values reported in the literature.