Parameter characterization of high-overtone bulk acoustic resonators by resonant spectrum method

Effects of electrode on high-overtone bulk acoustic resonator (HBAR) spectra are analyzed by numerical simulation. The figure of merit (FOM), the effective electromechanical coupling factor, keff2(m), and the quality factor Qs of the unique mode are discussed based on the resonance spectra of the HBAR. It is demonstrated that electrodes with proper acoustic impedance and thickness could improve the performance of the HBAR, or degrade the performance if the electrodes are not properly chosen.