Capacitive micromachined ultrasonic transducers (CMUTs) with isolation posts

We report on a capacitive micromachined ultrasonic transducer (CMUT) featuring isolation posts (PostCMUT) to solve a device reliability problem caused by charging during fabrication and operation, and to extend the device operation range beyond collapse voltage. The PostCMUTs were fabricated using a newly developed process based on the wafer-bonding technique. Paired tests showed the superior reliability characteristics of the PostCMUT design compared to those of earlier CMUT designs. The PostCMUTs showed no hysteresis during membrane-post contact.