A 1.75 GHz piezoelectrically-transduced SiC lateral overmoded bulk acoustic-wave resonator

This paper presents the development and study of a novel lateral overmoded bulk acoustic-wave resonator (LOBAR) using piezoelectric AlN on SiC technology. The SiC LOBAR is a new class of resonant devices in which multiple longitudinal vibrations are excited in a high quality factor (Q) acoustic cavity (SiC) by means of a miniaturized AlN transducer that occupies a small fraction of the device volume (210 μm³ of AlN versus 42,021 μm³ of SiC). The first LOBAR prototype reported herein exhibits a Q of 4250 for a series resonance at 1.75 GHz - one of the highest Q demonstrated for micro-resonators using piezoelectric transduction at GHz frequencies. The use of two materials capable of operations at high temperature and in harsh environments simultaneously offers high Q (SiC) and high transduction efficiency (AlN) and enables, for the first time, the development of RF MEMS components for a new realm of applications.