Modeling and simulation of Capacitive Micromachined Ultrasonic Transducer (CMUT)

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. Index Terms Capacitive Micromachined Ultrasonic Transducer, CMUT, Collapse voltage, Electrostatic Spring Softening Effect, Finite Element Analysis. Institute of Physics Publishing Journal of Physics: Conference Series 34 (2006) 595–600 doi:10.1088/1742-6596/34/1/098 International MEMS Conference 2006 595 © 2006 IOP Publishing Ltd