Design and Analysis of Lithium–Niobate-Based Laterally Excited Bulk Acoustic Wave Resonator with Pentagon Spiral Electrodes

Abstract

In this paper, we present a comprehensive study on the propagation and dispersion characteristics of A1 mode propagating in Z-cut LiNbO3 membrane. The A1 mode resonators with pentagon spiral electrodes utilizing Z-cut lithium niobate (LiNbO3) thin film are designed and fabricated. The proposed structure excites the A1 mode waves in both x- and y-direction by utilizing both the piezoelectric constants e24 and e15 due to applying voltage along both the x- and y-direction by arranging pentagon spiral electrode. The fabricated resonator operates at 5.43 GHz with no spurious mode and effective electromechanical coupling coefficient (Keff2) of 21.3%, when the width of electrode is 1 µm and the pitch is 5 µm. Moreover, we present a comprehensive study of the effect of different structure parameters on resonance frequency and Keff2 of XBAR. The Keff2 keeps a constant with varied thickness of LiNbO3 thin film and different electrode rotation angles, while it declines with the increase of p from 5 to 20 µm. The proposed XBAR with pentagon spiral electrodes realize high frequency response with no spurious mode and tunable Keff2, which shows promising prospects to satisfy the needs of various 5 G high-band application.

Keywords

• XBAR
• LiNbO₃ thin film
• effective electromechanical coupling coefficient