X-Cut Lithium Niobate S0 Mode Resonators for 5G Applications

This work presents the design, fabrication, and testing of S 0 mode YZ30° X-Cut Lithium Niobate Laterally Vibrating Resonators (LVRs) and degenerate Laterally Vibrating Resonators (d-LVRs) operating in the 3 to 16 GHz range for 5G applications. The resonator’s topology is optimized to extend the S 0 mode in the C-, X-, and K u -bands while preserving performance and mass-manufacturability. The devices are designed with acoustic wavelengths (λ) varying between 1.8 and 0.4 µm and fabricated on 100 nm thin film LN on high resistivity silicon 4" wafers with a 3-mask process. Experimental results highlighted quality factor at resonance (Q s ) and mechanical quality factors (Q m ) as high as 321 and 1318, respectively, and electromechanical coupling $\left( {k_t^2} \right)$ as high as 19.9%. Large $k_t^2$ (>10%) are recorded over a broad range of frequencies, (3 – 8 GHz), while Q m exceeding 100 are measured up to 15 GHz. Further enhancement to performance and range of operation on the same chip can be achieved by decreasing λ, refining the fabrication process, and optimizing the device’s design. These additional steps can help pave the way for the manufacturing of high-performance resonators on a single chip covering the full 1 – 25 GHz spectrum for novel 5G applications.