AlN/Al0.8Sc0.2N film S0 mode lamb wave resonator with spurious mode suppression

High-performance Lamb wave devices have a vast application prospect in modern wireless communication systems. This paper proposes a method of spurious mode suppression by reducing the overlap length of electrodes according to modal shapes. The AlN/Al0.8Sc0.2N composite film is used to achieve a trade-off between electromechanical coupling coefficient (k(t)(2)) and Q factor. The finite-element analysis (FEA) is employed to study the performance of the lowest-order symmetric mode (S-0) Lamb wave resonators (LWRs), and the FEA result shows a spurious mode in the impedance response. According to the results of modal shape analysis, the typical LWR, the LWR with the circle-shaped arrangement of electrodes, the LWR with the circle-shaped apodization, and the LWR with the arc-shaped apodization are fabricated to suppress the spurious mode and investigate the performance of the LWRs. The measurement results show that the spurious mode is effectively suppressed over a wide frequency range (1.9-2.2 GHz) by the three designed electrode configurations. The LWR with the circle-shaped apodization working at 2.023 GHz has a Q(p) factor of 955, a moderate k t 2 of 2.97%, a figure-of-merit ( Q x k(t)(2)) of 28.4, and a large value of f x Q x k(t)(2) (5.773 x 10(10)). Utilizing modal shapes to design the electrode configuration of LWRs can suppress spurious modes without significant performance deterioration. Published under an exclusive license by AIP Publishing.

Automated summary

This paper proposes a method of suppressing spurious modes in high-performance Lamb wave devices by reducing the overlap length of electrodes. The use of an AlN/Al0.8Sc0.2N composite film enables a balance between the electromechanical coupling coefficient (k(t)(2)) and Q factor. The study utilizes finite-element analysis and experimental fabrication of Lamb wave resonators with different electrode configurations to verify the effectiveness of spurious mode suppression.