Characteristic of LiNbO3 thin film ICP etching for micro/nano fabrication

Lithium niobate (LiNbO3), 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 LiNbO3 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 SiO2 mask. Based on the optimized etching process, LiNbO3 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 LiNbO3-based micro-acoustic devices.