Model for predicting spurious modes caused by fringing fields in lateral electrostatic actuators for MEM resonators

In this paper we present a generalized model for predicting the electromechanical behavior of longitudinal mechanical resonators including the effect of fringing fields on the excitation of spurious flexural modes. We demonstrate the validity and pertinence of our approach by applying our model to the prediction of the vibration amplitudes of square plate resonators. Measured amplitude spectra were obtained with a novel heterodyne interferometer, able to measure exact vibration amplitudes. Our model grasps with good accuracy the measured vibration amplitude, with vibration amplitudes in the order of 1-10 pm, over a range of 22-27 MHz, for both measurements and simulations.