A piezo-actuated on-chip testing device for the micromechanical characterization of the SiO2-polysilicon interface

Microelectromechanical systems (MEMS) have recently allowed to attain unprecedented results in different fields of applications, due to their versatile functionalities. In light of the continuous trend towards miniaturization, MEMS reliability is becoming more and more a critical concern, especially in dynamic environments characterized by shocks and repeated loadings. The interplay between the said external excitations and possible microfabrication defects, can detrimentally affect the long-term performance of inertial MEMS. In this research activity, focusing on the Silicon-on-Insulator (SOI) technology the reliability issues are studied as mainly driven by mechanical actions, in cases leading to a fatigue-induced delamination of polysilicon films from the substrate. By exploiting a piezoelectric actuation to induce vibrations characterized by kHz frequencies, the geometry of the movable parts of a testing device is optimized to maximize the stress leading to delamination. Results are presented for a statically-indeterminate structure, designed in order to cause a delamination of epitaxial polysilicon from silicon dioxide under cyclic loadings.