Impact of In-Plane Residual Stress on The Performance of The Film Bulk Acoustic Resonators

This paper presents the effect of in-plane residual stress on the design parameters such as resonance frequency and coupling coefficient of the Film Bulk Acoustic Resonator (FBAR) in accordance with the enhanced experimental buckling observed in the FBAR. The deformation in the film is due to the asymmetry of unequal top and bottom electrode thickness. The simulation models the individual impact that the residual stress has on the geometric and material properties of the thin piezoelectric film. The sensitivities of the individual impact provide design considerations for FBAR. The stack that has an equal thickness of the top and bottom electrodes provides less deformation and a predictive trend of frequency. The asymmetry can be used if slight tensile stress from the process integration can be obtained as it enhances the coupling coefficient.