2-16 GHz Multifrequency X-Cut Lithium Niobate NEMS Resonators on a Single Chip

Abstract: This work presents the design, fabrication, and testing of X-Cut Lithium Niobate (LN) acoustic nanoelectromechanical (NEMS) Laterally Vibrating Resonators (LVRs) and Degenerate LVRs (d-LVRs) operating in the S0 (YZ30) and SH0 (YZ-10) modes between 2 to 16 GHz range, monolithically fabricated on a single chip. The NEMS topology is optimized to extend the aforementioned fundamental modes in the C-, X-, and Ku-bands while preserving performance and mass manufacturability. The devices present acoustic wavelengths ({\lambda}) varying between 1800 and 400 nm and are fabricated on a 100 nm ultra-thin LN film on high resistivity silicon with a 3-mask process. Experimental results highlighted quality factor at resonance (Qs) and mechanical quality factors (Qm) as high as 477 and 1750, respectively, and electromechanical coupling (kt2) as high as 32.7%. Large kt2 (>10%) are recorded over a broad range of frequencies (2 - 8 GHz), while Qm 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 {\lambda}, refining the fabrication process, and optimizing device topology. These additional steps can help pave the way for manufacturing high-performance resonators on a single chip covering the entire 1 - 25 GHz spectrum.