Dual-electrode bimorph pmut arrays for handheld therapeutic medical devices

A CMOS-compatible, aluminum nitride (AlN) based, dual-electrode bimorph piezoelectric micromachined ultrasonic transducer (pMUT) array has been developed. Under an input 5V
_ac
driving voltage, a high acoustic intensity of 30-70mW/cm
²
up to 2.5mm deep into tissues can be generated for therapeutic medical applications. The low driving voltage is readily applicable for battery-powered low intensity pulsed ultrasound (LIPUS) medical devices for fracture and tissue healing applications. The fabrication also introduces a novel method using PECVD SiO
₂
as the barrier layer between AlN films to increase the breakdown voltage and manufacturing yield. Results on a prototype array have shown the highest intensity per voltage squared, per number of pMUTs squared, per piezoelectric constant squared (i.e. I
_n
=I/(VNd
₃₁
)
²
) among all reported pMUT arrays.