Accurate extraction of k_t^2 of piezoelectric film/substrate structure by conversion loss method for subtracting experimental acoustic losses in the substrate

摘要

Electromechanical coupling coefficient $(pmb{k}_{mathbf{t}}{}^{mathbf{2}})$ is an important parameter for determining the performances of RF BAW filter. The IEEE standard recommends a resonance-antiresonance method for determining the $pmb{k}_{mathbf{t}}{}^{mathbf{2}}$ of the piezoelectric films by using a self-standing film structure. The method for determining $pmb{k}_{mathbf{t}}{}^{mathbf{2}}$ from the film/wafer structure reduces the time and cost of wafer etching process. $pmb{k}_{mathbf{t}}{}^{mathbf{2}}$ is underestimated due to the acoustic losses in the substrate in the conventional conversion loss method, which can extract the $pmb{k}_{mathbf{t}}{}^{mathbf{2}}$ from HBAR. In this study, we introduce a method for subtracting the acoustic losses in the substrate.