Polysilicon MEMS fatigue and fracture characterization via on chip testing

In order to characterize the fatigue behaviour and determine the fracture energy of polysilicon used in micro-systems, an on-chip testing device has been designed and fabricated. The experimental set-up is able to continuously measure the elastic stiffness decrease and therefore to evidence fatigue of polysilicon 15-μm thick films and to allow for the introduction of a sharp crack at the notch of the tested specimen. A fracture test can be carried out, and, by combining experimental data and numerical simulations in the context of linear elastic fracture mechanics, an estimate of fracture energy can be obtained. In the paper it is also shown that numerical, cohesive approaches taking into account for the polycrystalline morphology can adopt the obtained fracture energy data in order to reproduce the experimental crack path.