Laterally Excited Bulk Acoustic Wave (LBAW) X-Cut Lithium Niobate Resonators

TL;DR

This paper introduces a novel LBAW resonator architecture on X-cut Lithium Niobate that enables multi-frequency operation, higher-order overtones, and improved RF performance through recessed electrode design and mode exploitation.

Contribution

It demonstrates for the first time higher-order overtones in LBAW resonators with recessed electrodes, enabling lithographic tuning and multi-frequency scaling on a single chip.

Findings

Achieved FoM of 437 at 673 MHz for fundamental mode

Achieved FoM of 53 at 1.05 GHz for overtone

Enabled on-chip multi-frequency scaling and frequency tuning

Abstract

In this work, Laterally excited Bulk Acoustic Wave (LBAW) resonators on X-cut Lithium Niobate (LiNbO3) and, for the first time their higher-order overtones (LOBAW) are demonstrated by embedding interdigitated electrodes recessed into the piezoelectric thin film, allowing to exploit both S0 and SH0 vibrational modes. This recessed electrode architecture decouples the dispersion relation from film thickness, enabling lithographic tuning of resonance frequency and on-chip multi-frequency scaling on a single substrate, while concurrently increasing static capacitance density (C0) and reducing ohmic losses (Rs). The excited SH0 modes exhibits Figures of Merit (FoM) of 437 at 673 MHz for the fundamental tone and 53 at 1.05 GHz for the overtone. The proposed architecture holds large potential for future 5G/6G advanced radio frequency front-end modules, enabling on-chip multi-frequency scaling and improved performance.