Large Coupling Acoustic Wave Resonators Based on LiNbO₃/SiO₂/Si Functional Substrate

In this work, wide band radio-frequency (RF) shear-horizontal surface acoustic wave (SH-SAW) resonators were designed and fabricated to attain a large effective electromechanical coupling (k
²
) over 35% near 1-GHz based on a thin-film lithium niobate (LiNbO
₃
/LN) on insulator layered substrate. In this study, the single-crystalline LiNbO
₃
thin film was bonded to a(100)-silicon carrier wafer with an intermediate silicon dioxide (SiO
₂
) layer to form a simple and low-cost hetero acoustic impedance waveguide. Fabricated resonators with Au-electrodes show scalable wavelengths from 3.2μm to 4.4μm (770 to 1008 MHz) featuring k
²
> 35% and Q of 250, which are sufficient for wide band RF filtering applications. Additionally, the potential of the SH-SAW resonator is demonstrated by a numerically synthesized ladder filter with a center frequency of 970 MHz, a 3-dB fractional bandwidth of 29.6%, and an insertion loss (IL) around 1.8 dB. It suggests the feasibility of developing wide bandwidth acoustic RF devices for potential 5G wireless communication through further design and fabrication optimizations.