A 20.4-GHz Lithium Niobate A3-Mode Resonator with High Electromechanical Coupling of 6.95%

Abstract

This work presents a third-order asymmetric (A3) mode Lamb wave resonator based on 128° Y-cut lithium niobite (LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> or LN) thin film operating at a super high frequency (SHF) up to 20.4 GHz. By exploring the possible electromechanical coupling coefficient (k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) of A3-mode resonator in LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> thin film of different orientations, we find that X-axis direction is the optimal direction to excite the A3-mode by applying horizontal electric field. Based on the analysis and simulation, spurious-free A3-mode resonator is designed and fabricated. The implemented device shows Q of 461 and k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 6.95%, the highest reported FoM (Q•k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) for piezoelectric MEMS resonators operating in this frequency range. The SHF operation and high k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of the A3-mode resonator show great potential of acoustic resonator technology for 5G millimeter wave (mm-Wave) applications.