Lamb Wave Resonators

Overview

Lamb waves are elastic waves that travel through thin plates, involving motion through the full thickness of the material. Lamb wave resonators use these waves in thin piezoelectric films—typically aluminum nitride (AlN) or lithium niobate (LiNbO₃)—patterned with metal electrodes to create a mechanical resonance at a desired frequency. Unlike bulk acoustic wave (BAW) devices, the resonant frequency is set by electrode spacing rather than film thickness, making it easy to fabricate multiple frequencies on a single chip.

Lamb wave resonators sit at the intersection of RF filtering and MEMS sensing. For wireless communications, they offer a compact, low-power way to build filters in the MHz-to-GHz range. For sensing, they are highly sensitive to surface mass changes, enabling chemical and biological detection. Their lithographic frequency definition, batch fabrication compatibility, and tunability through material and geometry make them a flexible platform for many applications.

Research today focuses on several key areas. Material development is a major theme: ScAlN and LiNbO₃ offer higher electromechanical coupling than conventional AlN, enabling wider filter bandwidths needed for 5G. Temperature stability is another challenge, typically addressed by adding SiO₂ layers to the resonator stack. On the applications side, researchers are developing Lamb wave filter banks for sub-6 GHz 5G bands (3.3–5 GHz) and exploring sensor arrays for gas detection and biosensing. Quality factor improvement—through better anchor design and surface treatment—is an ongoing effort across all these areas.