An Ultrathin Internal Dielectric Actuator for Extended Range Deflection Pull-in Free Actuation

MEMS electrostatic actuators suffer from pull-in instability, making them highly nonlinear and limiting their useful range of motion. This report resolves the performance-limiting issues of the gap-closing transducer by using an ultrathin dielectric layer (UDL) for actuation. The device has an electromechanical coupling coefficient of 4.26% and an average deflection sensitivity of 119 nm/V over a range of 350 nm for upto 3.3 V dc bias. The UDL capacitance and deflection show a square law dependence on voltage. The device can thus be used as an actuator upto the full range of motion with better performance. Additionally, the UDL or gap capacitance can be used for feedback to maintain constant gap or strain. UDL actuation may also be combined with gap actuation to lower the pull-in voltage without changing the gap or the actuator thickness. [2022-0213]