Modeling and simulation of Capacitive Micromachined Ultrasonic Transducer (CMUT)

Abstract

This work presents the modeling and analysis of CMUT using the MEMS simulation software, Coventorware. A rectangular membrane CMUT of area 40µm X 20µm with 0.2µm thickness of silicon nitride as the movable membrane was designed. To reduce the parasitic capacitance, silicon substrate with gold was used as the fixed bottom electrode, and the combination of aluminium and chromium were used as top electrode. The simulations were performed using Finite Element Modeling techniques. The various parameters greatly affecting the performance of CMUT such as resonant frequency, which decides the proper operation of CMUT as a transmitter or receiver and collapse voltage, the maximum voltage which the device can withstand are analyzed. It was also observed that the resonant frequency of the device decreases as the applied bias voltage increases. The changes were found due to the interesting effect known as electrostatic spring softening.