Effect of shapes and electrode material on figure of merit (FOM) of BAW resonator

Abstract

FBAR (Thin Film Bulk Acoustic Wave Resonator) devices are commonly used as application of RF (Radio Frequency) filters for the cell phones and other communication devices. This paper reports about the measurement of the efficiency of FBAR devices. The efficiency is commonly measured in terms of the EMCC (Electromechanical coupling coefficient) and QF (Quality factor). Since the FBAR devices are designed in many shapes and sizes which depend on their working frequency range. So every shape and size has a different value of QF and EMCC. This paper compares the various shapes in terms of QF, EMCC and spurious modes of L-Band (1-2 GHz) resonator. Once the best shape is selected, the study of different metal electrode materials coupling with piezoelectric layer and the effect of the thickness ratio (td) of electrode layer and the piezoelectric layer is discussed.