PROJECT TITLE :

Bimorph Piezoelectric Micromachined Ultrasonic Transducers

ABSTRACT:

This paper presents the concept, basic theory, fabrication, and testing results of twin-electrode bimorph piezoelectric micromachined ultrasonic transducers (pMUTs) for both airand liquid-coupled applications. Each the theoretical analyses and experimental verifications beneath the proposed differential drive scheme display high drive sensitivity and an electromechanical coupling energy efficiency that is as high as four× of the state-of-the-art pMUT with the same geometry and frequency. The prototype transducers are fabricated during a CMOS-compatible process with the radii of 100-230 μm using aluminum nitride as the piezoelectric layers with the thicknesses varying from 715 to 950 nm and molybdenum (Mo) because the electrodes with a thickness of 130 nm. The tested operation frequencies of the prototype transducers are 200-970 kHz in air for doable ranging and motion detection applications, and from 250 kHz to 1 MHz in water for medical ultrasound applications like fracture healing, tumor ablation, and transcranial sonothrombolysis. A twelve × twelve array structure is measured to own the highest intensity per voltage squared, per variety of pMUTs squared, and per piezoelectric constant squared (In = I/(V Nd31)a pair of) among all reported pMUT arrays. The generated acoustic intensity is in the range of 30-70 mW/cm2 up to a pair of.5 mm from the transducer surface in mineral oil with a driving voltage of five Vac, which is appropriate for battery-powered therapeutic ultrasound devices.