Nanomechanical studies and materials characterization of metal/polymer bilayer MEMS cantilevers

Abstract

Abstract Bilayer microelectromechanical components such as microcantilevers, microbridges or micromembranes are usually used in microtransduction for actuation and sensing. One layer achieves the structural and elastic recovery function and the other layer acts as the active part by deforming under actuations. This paper describes the studies of mechanical characteristics of flexible bilayer microcantilevers fabricated from the polymer SU8 with a reflective nano-metallic layer on the top. The mechanical characteristics investigated are stiffness, modulus of elasticity, resonant frequency, bending strain and stress. The analytical relationships for bending stiffness of bilayer microcantilevers are determined by using Castigliano's second theorem. The first bending resonant frequency is computed based on the lumped-parameter model. Experimental tests of mechanical characteristics and materials characterization are developed using atomic force microscopy and nanoidentation. Finite element analysis is used to determine the maximum stress in the sample layers and their mechanical responses.