Switchable and tunable film bulk acoustic resonator fabricated using barium strontium titanate active layer and Ta2O5/SiO2 acoustic reflector

Abstract

A solidly mounted acoustic resonator was fabricated using a Ba0.60Sr0.40TiO3 (BST) film deposited by metal organic chemical vapor deposition. The device was acoustically isolated from the substrate using a Bragg reflector consisting of three pairs of Ta2O5/SiO2 layers deposited by chemical solution deposition. Transmission electron microscopy verified that the Bragg reflector was not affected by the high temperatures and oxidizing conditions necessary to process high quality BST films. Electrical characterization of the resonator demonstrated a quality factor (Q) of 320 and an electromechanical coupling coefficient (Kt2) of 7.0% at 11 V.

Role of film stoichiometry and interface quality in the performance of (Ba,Sr)TiO3 tunable capacitors with high figures of merit

“…[1][2][3][4][5] A main focus of materials and device optimization is to simultaneously achieve high quality factors (Q ¼ 1/tand, where tand represents the dielectric loss tangent) while tuning the capacitance at least by a factor of two with an applied DC bias. 2,6 Q-factors exceeding 1000 and tunabilities up to 5:1 were reported in BST films that were grown by molecular beam epitaxy (MBE).…”