Fabrication of polymer-based wafer-bonded capacitive micromachined ultrasonic transducers

The fabrication process and characterization results of a single element capacitive micromachined ultrasonic transducer (CMUT) are presented in this paper. The fabrication process is based on polymer adhesive wafer bonding of silicon and low pressure chemical vapor deposited silicon nitride wafers. The fabricated transducer has an average resonant frequency of 5.5 MHz in air. In immersion, the transmitted ultrasound signal from the transducer was measured to show a centre frequency of 4.9 MHz with a 3dB bandwidth of 114%. The capability of receiving ultrasound signal was also demonstrated using an off-the-shelf transducer. Initial characterization results suggest that the proposed technique can be an attractive alternative for CMUT fabrications.