SH₁ mode plate wave resonator on −27°YX LiTaO₃ single crystal plate with phase velocity of 12 km s⁻¹

Abstract This study presents a first shear horizontal (SH 1 ) mode plate acoustic wave resonator on a −27°YX LiTaO 3 (LT) thin plate. The SH 1 wave is generated when a backside electrode is formed on the opposite side of an interdigital transducer (IDT). Two resonators, one with Cu and the other with an Al backside electrodes, along with a Cu IDT were simulated and fabricated. Both fabricated SH 1 resonators exhibited high phase velocities of 12 km s −1 and bandwidth (BW) of around 4.5%. The temperature coefficient of frequency is −38 ppm °C −1 at resonance and −56 ppm °C −1 at anti-resonance on a 0.13 λ thick LT plate. Although the backside electrode is necessary for high coupling of the SH 1 wave, it increases the clamp capacitance of the devices, resulting in low impedance characteristics of around 10 Ω and low impedance ratios around 30 dB. Additionally, the suppression of spurious responses is necessary for filter application.