Redeposition-Free Inductively-Coupled Plasma Etching of Thin-Film Lithium Niobate on Insulator

Argon ion etching of lithium niobate on insulator (LNOI) in an inductively coupled plasma (ICP) system has so far shown the best optical quality devices in the context of integrated photonics due to the polishing character of the argon process [1–3]. However, micromasking from material redeposition and chamber contamination introduced during etching (Fig. 1(A)) and the close to one etch selectivity for deep etches still make it a challenging process. Comprehensive studies have already been conducted on the etching of LNOI, showing the linearity and reliability of the process [3], but to our knowledge no study has been done on the redeposition itself. Here we present the results from our recently published work [4]. Starting from a hard mask with a 85° sidewall angle, we undertake an in depth study on the properties of the redeposition, trenching, etch homogeneity and final sidewall angle with varying ICP chamber pressure and DC bias (Fig. 1 (B, C, D)).