3-D Ultrasonic Fingerprint Sensor-on-a-Chip

A fully integrated 3-D ultrasonic fingerprint sensor-on-a-chip is presented. The device consists of a 110× 56 piezoelectric micromachined ultrasonic transducer (PMUT) array bonded at the wafer level to custom readout electronics fabricated in a 180-nm CMOS process with a HV (24 V) transistor option. With the 24 V driving signal strength, the sensor consumes 280 μJ to image a 4.73 mm × 3.24 mm section of a fingerprint at a rate of 380 fps. A wakeup mode that detects the presence of a finger at 4 fps and dissipates 10 μW allows the proposed sensor to double as a power switch. The sensor is capable of imaging both the surface epidermal and subsurface dermal fingerprints and is insensitive to contaminations, including perspiration or oil. The 3-D imaging capability combined with the sensor's sensitivity to the acoustic properties of the tissue translates into excellent robustness against spoofing attacks.