Pulse-echo ultrasonic fingerprint sensor on a chip

A fully-integrated ultrasonic fingerprint sensor based on pulse-echo imaging is presented. The device consists of a 24×8 Piezoelectric Micromachined Ultrasonic Transducer (PMUT) array bonded at the wafer level to custom readout electronics fabricated in a 180-nm CMOS process. The proposed top-driving bottom-sensing technique minimizes signal attenuation due to the large parasitics associated with high-voltage transistors. With 12V driving signal strength, the sensor takes 24μs to image a 2.3mm by 0.7mm section of a fingerprint.