K-band LiNbO3 A3 Lamb-wave Resonators with Sub-wavelength Through-holes

TL;DR

This paper introduces a novel through-hole design in K-band LiNbO3 Lamb-wave resonators that maintains performance while reducing suspension area, enhancing stability, and standardizing fabrication without additional processing.

Contribution

It validates the first use of sub-wavelength through-holes in Lamb-wave resonators, demonstrating improved stability and fabrication consistency without performance loss.

Findings

Maintains frequency, coupling coefficient, and quality factor with through-holes

Reduces ineffective suspension area of the piezoelectric film

Facilitates standardization of etching processes across wafers

Abstract

Addressing critical challenges in Lamb wave resonators, this paper presents the first validation of resonators incorporating sub-wavelength through-holes. Using the A3 mode resonator based on a LiNbO3 single-crystal thin film and operating in the K band as a prominent example, we demonstrate the advantages of the through-hole design. In the absence of additional processing steps, and while maintaining device performance--including operating frequency, electromechanical coupling coefficient, and quality factor--without introducing extra spurious modes, this approach effectively reduces the ineffective suspension area of the piezoelectric LN film, potentially enhancing mechanical and thermal stability. It also standardizes etching distances (and times) across various Lamb wave resonators on a single wafer, facilitating the development of Lamb wave filters. The versatility of the through-hole technique, with relaxed constraints on hole geometry and arrangement, further highlights its significance. Together with the other advantages, these features underscore the transformative potential of through-holes in advancing the practical implementation of Lamb wave resonators and filters.