Fabrication and characterization of AlN based Piezoelectric Micromachined Ultrasonic Transducer for contact sensing

In this paper, we present an aluminum nitride (AlN) based Piezoelectric Micro-machined Ultrasonic Transducer (PMUT) for contact sensing, which is a suspended stacked layers Si/Mo electrode /AlN/Al electrode in Silicon substrate. In order to obtain a Si elastic layer with a small thickness, DRIE Si process is utilized to make a deep cavity on the backside of Si substrate to suspend the stacked layers of PMUT device. AlN based PMUT sample is fabricated, having a suspended stacked layers of Si/Mo/AlN/Al measured about 5μm/0.1μm /0.8μm/1μm respectively in the thickness, 100μm in the radius of Si film. The AlN film has a measured surface roughness of 5nm by AFM and has (001) orientation peak by XRD analysis.