BCB polymer based row-column addressed CMUT

The number of transmit and receive channels needed to perform real-time 3-D ultrasonic imaging can be greatly reduced if row-column (RC) addressed 2-D transducer arrays are used. However, fabricating RC CMUTs have shown to be challenging. The difficulties are typically stress issues related to the high temperature processes and charging effects related to mobile charges in dielectric thin films, overall resulting in low yield and/or a time dependent performance. To overcome these problems a polymer adhesive bonding with Bisbenzocyclobutene (BCB) can be used, and previous work [1] has shown promising results for a single element. This contribution presents a realization of BCB for RC CMUTs with BCB-to-Silicon bonding on a quartz substrate.