Quality Factor Improvement of 30° Y-cut Lithium Niobate SH-SAW Resonators Using Double Busbar Structure

With the rapid development of wireless communication technology, the demand for high performance acoustic resonators is increasing. Currently, the quality factor (Q) of shear horizontal surface acoustic wave (SH-SAW) resonators with large electromechanical coupling coefficients (${k^2}_{{\text{eff}}}$) is limited due to large acoustic loss. Therefore, a double busbar structure is proposed in this work to reduce the transverse energy loss in 30°Y-cut LiNbO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (LN) /SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/poly-Si/Si SH-SAW resonators. The double busbar structure can effectively reduce the transverse energy leakage and captures more acoustic energy in effective aperture region of the interdigital transducer (IDT). Compared with the Q of the conventional busbar structure resonator (1298), the measured Bode-Q<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> (1823) of resonator with double busbar structure achieves a 40% enhancement without sacrificing ${k^2}_{{\text{eff}}}$. It is verified that the proposed double busbar structure is an effective solution to improve the Q of LN-based SH-SAW resonator.