Fabrication of SU-8 based Capacitive Micromachined Ultrasonic Transducer for low frequency therapeutic applications

In this paper we present a simple post-CMOS compatible sacrificial release method of fabricating SU-8 based Capacitive Micromachined Ultrasonic Transducer (CMUT) for low frequency therapeutic applications. CMUTs fabricated with Silicon Nitride and Silicon Dioxide lay constraints in terms of area and power consumption especially in the low frequency range. Fabrication of these devices need complex high temperature processes that makes them incompatible for post-CMOS processing. Analytical modeling shows that SU-8 based CMUT consumes less area (below 25%) and power compared to Silicon Nitride and Silicon Dioxide based CMUTs. The proposed fabrication method overcomes inherent disadvantages of sacrificial release method by providing uniformity in air gap and reducing the possibility of stiction.