High-Q Coupled Mode Resonator Based on Wafer-Level Transfer Technology

Abstract

This article presents a high quality factor (Q value) coupled mode Lamb wave resonator (LWR) based on an AlSc0.095N thin film and introduces a novel fabrication process applied to LWRs with an IDT-IDT structure. To address the issue of multiple resonance modes that are excited in IDT-Floating LWRs within the 1.5–3-GHz frequency range due to the close phase velocities of acoustic modes, the proposed IDT-IDT LWR configuration enables the degenerate excitation of multiple acoustic modes. Further optimization of the number of IDT fingers and the width of the reflective boundary effectively suppresses in-band spurious mode. By incorporating an acoustic speeder structure, anchor loss is significantly suppressed, enhancing the Q value. To address the manufacturing challenges of IDT-IDT structured resonators, a fabrication process based on wafer-level transfer technology is proposed. The fabricated AlSc0.095N film with a thickness of 770 nm achieves a full-width at half-maximum (FWHM) value of 1.18°. The LWR fabricated with this process, operating at 2.27 GHz, achieves a Bode-Q value of 1307, and the electromechanical coupling coefficient ( ${k}_{t}^{{2}}$ ) reaches 5.17% at a 9.5% Sc doping concentration. The proposed LWR with IDT-IDT structure shows an advantage in the figure of merit (FoM $= {Q} \times {k}_{t}^{{2}}$ ) compared to other LWRs operating in the 2–3-GHz frequency range, achieving a value of 67.57.