Monte Carlo simulation of micro-cracking in polysilicon MEMS exposed to shocks.

In this work we discuss a multi-scale framework to model the shock-induced failure of polysilicon micro electro-mechanical systems (MEMS), specifically focusing on the impact of uncertainties at polycrystal length-scale on the results. Even though the MEMS sensors usually fail almost instantaneously when subject to shocks, the length of the zone where micro-cracking takes place amounts to 10-20% of the characteristic grain size. Therefore, in the micro-mechanical simulations the morphology of polysilicon films constituting the movable parts of the MEMS has to be explicitly modeled, and a cohesive approach to micro-cracking is adopted. Forecasts of failure are obtained through a Monte Carlo methodology, wherein statistics of the polycrystalline morphology are appropriately accounted for. Outcomes are shown to accurately describe failures usually observed in broken inertial micro-devices.