Out of plane vs in plane flexural behaviour of thin polysilicon films: Mechanical characterization and application of the Weibull approach

A new MEMS for on-chip mechanical testing of 0.7 μm thick LPCVD polysilicon film has been designed, modelled and fabricated. The polysilicon film is electrostatically loaded under bending until rupture in the out of plane direction. Electrostatical numerical simulations were carried out to evaluate the force developed by the actuator and the capacitance measured by the sensing electrodes while structural numerical simulations were used to compute the stress field into the specimen and its stiffness. Elastic properties and ultimate strength of the material were determined. Comparative studies were performed to investigate the variation of the ultimate strength of the polysilicon film with different loading conditions.