A DC Voltage Dependant Switchable Thin Film Bulk Wave Acoustic Resonator Using Ferroelectric Thin Film

Abstract

In this paper, a new application of ferroelectric thin film based on electrostrictive and piezoelectric effects is reported. Electrostrictive resonances in the thin film can be controlled with the application of the DC electrical field. A switchable thin film bulk wave acoustic resonator (FBAR) is proposed using barium strontium titanate (BST) thin film. The measured resonator has a parallel resonance at 2.035 GHz and a series resonance at 1.975 GHz with 25 V DC bias applied. The electromechanical coupling coefficient was calculated to be approximately 7.07% which is comparable to AIN FBARs. Acoustic parameters of BST thin film were extracted by optimizing the resonator's transmission line model to fit the measurement results. Simulation results for a switchable BST FBAR filter operating at 2 GHz are also presented.