Epitaxial Pb(Zr,Ti)O3-Based Piezoelectric Micromachined Ultrasonic Transducer Fabricated on Silicon-On-Nothing (SON) Structure

This study reports the fabrication method of a piezoelectric micromachine ultrasonic transducers (pMUTs) using a Silicon on Nothing (SON) structure and a monocrystalline thin film of lead zirconate titanate (PZT). For the SON structure, an array pattern of small hole was fabricated on a (100) Si substrate. Hydrogen annealing was then used to induce Si reflow. As a result, a plate-shaped cavity with a thickness of 0.5 μm was formed under a (100) Si diaphragm of 75 μm diameter. PZT was epitaxially grown on the diaphragm via buffer layers. A pMUT was fabricated and preliminarily characterized. The merits of this fabrication method include single side process, no release and sealing process and compatibility with most of major piezoelectric materials.