Dynamic analysis of MEMS based tensile testing structures for thin films mechanical characterization

As MEMS devices become ubiquitous in modern technologies, a proper knowledge of the mechanical and material properties of the structural layers of these devices becomes critical. The need for accurate micro-scale characterization of material properties has triggered a flood of characterization techniques. Motivated by the practical and scientific importance of thin films, the work presented in this dissertation, aims to study the dynamics of MEMS tensile stages and provide a method for estimating stress that is based on the out-of-plane flexural resonance of the test structures. More precisely, a one dimensional (1D) dynamic analysis is performed based on two different techniques: (i) the Euler-Bernoulli beam equation and (ii) the Rayleigh-Ritz approach. Two types of structures were fabricated and tested for this work, the first having a 330 nm thick Palladium film as the test material, and the other having sc Si as the test material. This thin film testing approach was extended in the case of sc Si to study the impact of the sample’s thickness on the apparent extensional Young’s modulus. Indeed a dependence of the Young’s modulus of the sc Si on the sample thickness was observed, the variation in the extensional elasticity reached almost 50% for ultrathin sc Si beams.
(FSA 3) -- UCL, 2012