Piezoelectric Micromachined Ultrasonic Transducers with Corrugated Diaphragms Using Surface Micromachining

A key metric of micromachined ultrasonic transducer (MUT) performance is the volume velocity, which determines the transmitting output pressure. Here, we present a study to demonstrate corrugated-diaphragm piezoelectric MUTs (PMUTs) which have up to 3.2X higher volume velocity than conventional PMUTs of the same area. The PMUTs are manufactured by a surface-micromachining process forming a high fill-factor (80%) array, and corrugations can be added without any additional masks or process steps. The PMUTs with corrugations are implemented to have the increased displacement and resonant frequency. The corrugations and released holes are etched and formed by the same fabrication step, and their opening-area ratios determines the corrugation depth which is critical to PMUT efficiency. By corrugating PMUT diaphragm, it provides a simple method to tune resonant frequency. The study includes design, fabrication, and characterization for the various approaches to corrugated PMUTs.