Minimization of nonlinearities in nano electrostatic drive actuators using validated coupled-field simulation

A recently introduced new CMOS compatible actuator class, called nano electrostatic drive (NED), uses electrostatic actuation to provide significant deflections of elastic structures. The behavior of such actuators can be dominated by nonlinear phenomena, if the nonlinearities are not understood and not considered in the design. One of the main nonlinearity sources is the electrostatic actuation, which results in the well-known instability named pull-in. Additionally, due to large deflections provided by NED technology, stress stiffening and large deformation significantly influence the system, shifting the eigenfrequencies, altering the pull-in voltage, or even introducing geometrical buckling. All these effects together characterize static and dynamic behavior and can be tailored to partially counterbalance each-other by specific designs. In following, we use finite element method (FEM) to analyze the static and dynamic behavior of MEMS based on NED technology. Owing to coupled-field FEM technique, we observe effects like static pull-in, electromechanical eigenfrequency shift and transient phenomena in detail. The numerical results are validated during optical experiments, which supports the conclusions arose from the FEM. Finally, characterizing of the nonlinearities grants the ability to tailor and minimize them during the MEMS design process.