A study of adhesion forces in thick epitaxial polysilicon under dynamic impact loading

The work presents a structure and a method for the in-line characterization of impacts and adhesion phenomena between MEMS moving and fixed parts: the focus is on the monitoring of an inertial proof mass motion when colliding with a mechanical stopper. Through such measurements, one can evaluate the energy balance during impact events. The work analyzes the adhesion force evolution after a number of impact cycles comparable or larger than shocks in a 5-year operation. Results obtained on two different specimens show growing and then stabilizing adhesion forces of on average 170 nN, under impact cycles with about 500 fJ energy loss. No marked dependence on the specimen area is obtained. The possibility to change and track the impact kinetic energy is also demonstrated.