Polymer-based Capacitive Micromachined Ultrasonic Transducers (CMUT) for Micro Surgical Imaging Applications

The design, simulation, and fabrication results for a first generation polymer CMUT are presented. Baseline ANSYS and MATLAB simulations show that the use of a silicon nitride membrane should increase the transmission signal by 28% and the receiver sensitivity by 33%, when compared to a conventional poly silicon membrane. Simulations with a polymer membrane showed a maximum membrane deflection increase up to 67%, at approximately 6.5 MHz, when compared to nitride. Furthermore, the optimal mechanical impendence coupling frequency was lowered to 3.7 MHz for the polymer. These simulations give design guidelines for a CMUT based on geometric parameters such as membrane length and thickness. A CMUT array was then designed and fabricated with a target DC actuation voltage of less than 50V. Also, results showed potential operation of the CMUT up to 10 MHz using a low temperature fabrication process that still results in durable operation