Two-dimensional capacitive micromachined ultrasonic transducer (CMUT) arrays for a miniature integrated volumetric ultrasonic imaging system

in medical applications, CMUTs reported on so far have broader fractional bandwidth (FBW) but lower transduction efficiency (TX and RX) [1]. Most fabricated CMUTs reported in the literature carried membranes of uniform thickness. Since there is a performance trade-off between transduction efficiency and FBW when designing CMUTs with uniform membrane thickness, there is limited room for performance improvement in these devices. However, wafer-bonding-based CMUT fabrication provides design flexibility by allowing fabrication of membranes with differen