3.2 GHz first shear horizontal mode plate wave resonator on 175°YX LiNbO3 thin plate showed 24.6% bandwidth

In this study, a first shear horizontal (SH1) mode plate wave resonator for high-frequency and wide-band filters was investigated. From FEM simulation, SH1 mode plate wave exhibited a high phase velocity of 23 km/s and a high electro-mechanical coupling factor (k2) of 37% on (0°, 85°, 0°) LiNbO3 (LN) with a thickness of 0.1λ (λ: wavelength). The SH1 mode resonator was fabricated on a 0.5-0.57 µm thick LN film. An 80 nm Al IDT electrode was formed with λ varied from 4-16 μm. Finally, 50 nm thick Al was deposited to form an electrically short bottom plane, which was required to generate an SH1 mode wave. The fabricated device exhibited a resonance frequency (fr) of 2.24 GHz, an anti-resonance frequency (fa) of 2.8 GHz, a wide fractional bandwidth (FBW) of 20%, an impedance (Z) ratio of 35.4 dB, and TCF of -90.8 ppm/°C at fr and -74.8 ppm/°C at fa.