Spurious-Free SAW Resonators Using Lithium Tantalate on Silicon Carbide Substrate with Rhomboidal Apodization IDT

With the rapid development of 5G communication technology, the performance of surface acoustic wave (SAW) resonators using hetero-layered structure urgently needs to be further improved. For instance, the transverse modes can significantly reduce the performance of SAW devices. Herein, a strategy by employing rhomboidal apodization interdigital-transducer (IDT) was proposed to suppress the spurious modes, and thus spurious-free 42° <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Y$</tex>-cut <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{LiTaO}_{3}/\text{SiO}_{2}/\alpha-\text{Si}/\text{SiC}$</tex> SAW resonators were successfully implemented. The experiment results have verified the successful suppression of transverse modes when the rhomboidal apodization IDT is adopted. The resonant frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(f_\mathrm{r})$</tex> of fabricated SAW resonators is around 1 GHz. Moreover, the SAW resonator with normal IDTs exhibits a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$k_{\mathrm{e}\mathrm{f}\mathrm{f}}^{2}$</tex> of 11.4% and a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bode}-Q_{\max}$</tex> of 2160. The resonator with rhomboidal apodization IDTs exhibits a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$k_{\mathrm{e}\mathrm{f}\mathrm{f}}^{2}$</tex> of 10.9%, a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bode}-Q_{\max}$</tex> of 2185 and the transverse mode has been suppressed.