A Spurious-Free SAW Resonator With Near-Zero TCF Using LiNbO3/SiO2/quartz

As a promising material alternative, lithium niobate (LN)-based heterostructure has recently received growing recognition in the field of radio frequency (RF) wideband filtering. However, the corresponding surface acoustic wave (SAW) devices still encounter spurious transverse modes interference and deficient thermal stability, which hinder their capability to process the already crowded spectrums. This work presents spurious-free and near-zero drift shear horizontal SAW (SH-SAW) resonators utilizing an LN-on-quartz (Qz) platform. Guided by the finite element method, we first analyzed the slowness dispersion for various SAW materials. The proposed LN/SiO2/69°Y-90°X Qz heterostructure exhibits superiority in suppressing spurious transverse modes, which has been theoretically and experimentally evidenced by comparing its passband behavior with the performances of SH-SAW resonators employing typical silicon and silicon carbide substrates. Furthermore, with 69°Y-90°X Qz, a near-zero temperature coefficient of antiresonance frequency of -1.42-ppm/°C was successfully realized in LN heterostructure-based devices for the first time. The demonstrated LN/SiO2/Qz platform herein can facilitate gigahertz, spurious-free, and stable RF wideband applications.