Amorphous Silicon for Parasitic Surface Conduction Effect Elimination of SAW Resonators

This work presents a surface acoustic wave (SAW) resonator based on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{LiTaO}_{3}/\text{SiO}_{2}/\text{amorphous}$</tex> silicon <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\alpha$</tex>–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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha$</tex>–-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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$k^{2}{}_{\text{eff}}$</tex> of 11.6%. The performance has shown the strong potential of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{LiTaO}_{3}/\text{SiO}_{2}/\alpha-\text{Si}/\text{Si}$</tex> multilayer substrate for the front-end applications in 5G.