Amorphous Silicon for Parasitic Surface Conduction Effect Elimination of SAW Resonators

This work presents a surface acoustic wave (SAW) resonator based on $\text{LiTaO}_{3}/\text{SiO}_{2}/\text{amorphous}$ silicon $(\alpha$–Si)/crystalline silicon (c-Si) multilayer substrate. Oxide-passivated high resistivity (HR) wafers lead to experiencing parasitic surface conduction (PSC) caused by fixed charges in the oxide. A thin layer of $\alpha$–-Si eliminates the PSC effect to reduce substrate loss. The substrate loss is extracted by coplanar waveguide structure in HFSS. The fabricated resonator shows a high Bode-Q of 2040 and $k^{2}{}_{\text{eff}}$ of 11.6%. The performance has shown the strong potential of the $\text{LiTaO}_{3}/\text{SiO}_{2}/\alpha-\text{Si}/\text{Si}$ multilayer substrate for the front-end applications in 5G.