Piezoelectric micromachined ultrasonic transducer with air-backed cavities

A piezoelectric micromachined ultrasonic transducer comprising asubstrate and a first dielectric film formed on the substrate. Anopening having a sidewall is formed through the substrate and firstdielectric film. A bottom electrode is formed on the firstdielectric film spanning the opening. A piezoelectric element isformed on the bottom electrode. A second dielectric film surroundsthe piezoelectric element. A conformal insulating film is formed onthe sidewall of the opening. A conformal conductive film is formedin contact with the bottom electrode and on the sidewall of theopening, wherein an open cavity is maintained in the opening. A topelectrode is formed in contact with the piezoelectric element.

Dausch, D. (2008). IPC No. U.S. Piezoelectric micromachined ultrasonic transducer with air-backed cavities. (Patent No. 7449821).