Influence of initial stresses on resonance properties of FBAR

This paper investigated the effects of initial stresses on resonance properties of Film Bulk Acoustic Resonator (FBAR) in thickness-stretch mode. Based on the fundamental piezoelastic equations of piezoelectric material with initial stress, the vibration equation of ideal FBAR under sine excitation voltage is derived. The solution is then obtained by using of the boundary conditions. The series and parallel resonance frequency are presented, and the effects of initial stresses on resonance frequency, bandwidth, and effective electromechanical coupling coefficient are discussed. A numerical example is presented to show the effects. These results are very useful for the improvement of designing FBAR.