Piezo-actuated MEMS testing devices for materials characterization at the microscale

Microelectromechanical systems (MEMS) are small-scale devices that have already revolutionized a number of high-tech fields, owing to their versatile functionalities. However, there is still concern regarding their reliability, especially when they have to operate in harsh environments characterized by high temperature and humidity levels. The unknown behavior of the relevant structural parts under varying loading, as affected by possible microfabrication defects, can spoil the long-term performance of the devices. In this work, the reliability problem has been addressed by investigating the fatigue-induced delamination processes in polysilicon-based MEMS structures. Ad-hoc designed test structures featuring a piezoelectric actuation have been designed, aiming to maximize the stress state in regions susceptible to the said delamination events. An optimization strategy for the topology/shape of the test structures has been then proposed by taking advantage of a numerical investigation, to allow for all the possible dissipative phenomena that characterize the response of the movable structures at the microscale, including their interaction with the surrounding fluid.