MEMS reliability study in shock environments through numerical and experimental investigations

This paper reports a novel method to evaluate and improve the reliability of mechanical stops during design and validation phases of MEMS (Micro ElectroMechanical System) in shock environments. Firstly, inplane stop contact behavior is modeled through both steady-state and dynamic mechanical FEM (Finite-Element Modeling) to validate physics package and to extract nonlinear stiffness and stress distribution as functions of contact force applied on a cylinder-to-plane Hertz contact type. Then, the transient response of a MEMS including stops behavior is modeled with a lumped impact element approach which allows to compute contact force as a function of applied half-sine shock parameters. Finally, several shock tests have been performed on numerous devices embedding previously modeled stops to evaluate experimental survival rate. Fitting experimental data to numerical results combined with Weibull theory exhibits a good compliance which allows to estimate silicon Weibull parameters respectively at 0.7 GPa, 1.1 GPa and 4 for threshold stress, average stress and Weibull modulus.