Aluminum Nitride Combined Overtone Resonator for Millimeter Wave 5g Applications

This paper presents the first Aluminum Nitride (AlN) Combined Overtone Resonator (COR) in the 5G millimeter wave (mmWave) spectrum. The demonstrated AlN COR operates based on a multimodal excitation of the second and third order asymmetric Lamb-wave modes (A2 and A3) in a 389 nm thick AlN film. The combined overtone is observed at 23.2 GHz with a high electromechanical coupling coefficient, $k_t^2$, of 0.46% (Lateral-Field-Excited configurations with only top electrodes) and mechanical quality factor (Q m ) of 254, providing a high f · Q >6e12. Additionally, the two-dimensional vibration mode of CORs allows the resonant frequency to be lithographically defined without significant $k_t^2$ degradation. The demonstrated performance makes AlN CORs a strong candidate for the implementation of low-loss miniaturized multi-frequency filters for mmWave 5G applications.