A Two-Port Multiple Moving Membrane Capacitive Micromachined Ultrasonic Transducer with Reduced Effective Height and Enhanced Sensitivity

This paper presents a theoretical model and an experimental validation of a two-port multiple moving membrane capacitive micromachined ultrasonic transducer. The developed transducer includes a stack of two flexible membranes suspended on a fixed electrode. The transducer is fabricated utilizing a sacrificial technique, PolyMUMPs, and with a resonant frequency of 1.8 MHz. Electrical measurements are conducted using an impedance analyzer in order to investigate the influence of the transducer's additional moving membrane on the device effective cavity height. This, consequently, influences the transducer acoustic power generation. The deigned two port transducer enables a dynamic change in the effective cavity height through adjusting the applied DC bias voltage. The experimental results validate this hypothesis and are shown in agreement with the theoretical results.