Experimental Study on Frequency Stability of Micromechanical Resonators Operating in the Nonlinear Tapping Mode

Frequency stability of micromechanical resonators operating in the nonlinear tapping mode was investigated. In particular, a CC-beam oxide-rich resonator based on a CMOS-MEMS process platform exhibits higher frequency stability at the bifurcation points in the nonlinear tapping frequency transmissions, yielding a ~2× improvement of short-term Allen deviation compared to that at the midpoint of the tapping regime and that operating under the regular nonlinear spring softening (not entering the tapping mode yet). Differing from the previous studies on stability of MEMS resonators in either nonlinear softening or hardening condition [1] [2], this work explores the frequency stability deeper into the tapping mode of MEMS resonators-essentially behaving as resoswitches with no electrical current flowing through the contact-where the devices are subject to highly nonlinear repulsive forces due to impact. The results would help facilitate not only the understanding of the nonlinear dynamics of resoswitches but also the determination of optimum operating points of the devices.