Characteristic of LiNbO 3 thin film ICP etching for micro/nano fabrication

Abstract Lithium niobate (LiNbO 3 ), renowned for its use in surface acoustic wave devices, faces significant challenges in achieving high-quality micro/nano fabrication due to its chemical inertness and limited etching precision. In this work, the inductively coupled plasma (ICP) etching of LiNbO 3 thin films is systematically investigated and optimized by examining the effects of RF bias power, chamber pressure, and Cl₂/Ar/H₂ gas flow ratios. An optimized ICP etching recipe is identified, consisting of an ICP power of 600 W, an RF bias power of 120 W, a chamber pressure of 10 mTorr, and gas flow rates of Cl₂/H₂/Ar = 10/20/50 sccm. Ultimately, a steep sidewall angle of 79.1° was obtained by the final optimized recipe, with an etching rate of approximately 32 nm min −1 , and a selectivity of 1.43:1 relative to SiO 2 mask. Based on the optimized etching process, LiNbO 3 lateral vibration resonators are successfully fabricated and characterized. A representative resonator operating at approximately 400 MHz exhibits a high quality factor exceeding 1750, demonstrating the practical effectiveness of the optimized ICP etching process for enabling high-performance LiNbO 3 -based micro-acoustic devices.