13 GHz Acoustic Resonator with Q of 600 in High-Quality Thin-Film Aluminum Nitride

This study reports a high-quality thin-film aluminum nitride (AlN) acoustic Lamb wave resonator (LWR) with a compact size and low-loss operation. The device is composed of 60 nm thick Al electrodes on the top of 200 nm thick plasma vapor deposition (PVD) AlN film. The design and stack of the resonator are selected for leveraging of Ku-band operation (12-18 GHz) with top electrodes of wavelengths (λ, 0.5-0.8 µm). Specifically, λ of 0.8 µm implements a 13.0 GHz resonator with a record-breaking Qp_3dB of 600, enabled by fundamental symmetric (S0) mode surpassing prior works. The results highlight the potential for the effectiveness of the new stack and optimized resonator design in Ku-band. Further study will be focused on identifying and minimizing the dominant loss.

I. Introduction

Radio frequency (RF) piezoelectric-based acoustic filters have been the main technology used as sub-6 GHz front-end solutions [1]–[3]. Piezoelectric acoustic devices operating at radio frequencies (RF), where electromagnetic signals are transformed into mechanical vibrations, are promising due to the significantly shorter wavelengths of acoustic waves, about five orders of magnitude smaller than electromagnetic waves, allowing for more compact resonators and waveguiding structures [4]–[6]. With wireless communication moving into higher frequency bands, acoustic filters are expected to be developed, especially for the frequency range of 12-18 GHz, known as Ku-band, offering a balanced advantage in terms of both spectral efficiency and coverage, promising for 6G midbands [7], [8]. Additionally, it enables less demanding technology requirements due to its lower operational frequency, which could facilitate a quicker commercial rollout compared to millimeter waves. Moreover, this spectrum segment is expected to be reallocated for 6G midband use [9]. Such systems require miniature front-end elements capable of low-loss operation at the Ku band [10].