Post-CMOS Compatible Piezoelectric Micro-Machined Ultrasonic Transducers

Fingerprint sensing is pervasive in the cellular telecommunications market. Current commercial fingerprint sensors utilize capacitive scanning. This work focuses on the design, fabrication and characterization of post-complementary-metal-oxide-semiconductor (CMOS) compatible piezoelectric micro-machined ultrasonic transducers for use as ultrasonic pixels to improve robustness to contamination and allow for sub-epidermis scans. Ultrasonic pixels are demonstrated at frequencies ranging from 100 kHz to 800 kHz with several electrode coverages and styles to identify trends.