Thin film LiNbO₃ surface preparation using SC-1

This study investigates the use of Standard Cleaning 1 (SC-1), a routine treatment in silicon micro-/nano-fabrication, as a step in the processing of photonic structures and waveguides on thin films of lithium niobate on insulator (LNOI). We investigate the use of SC-1 for surface preparation and as a cleaning method to remove residual byproducts after ICP etching, evaluating its impact on etching dynamics and the quality of the LiNbO 3 thin film. Our results demonstrate that SC-1 cleaning removes a surface layer of LiNbO 3 characterized by higher oxygen vacancies. These oxygen vacancies accelerate the etching process and lead to faster under-etching of Si 3 N 4 capping layers on LiNbO 3 , causing pattern delamination, particularly at sub-micron scales where under-etching is more detrimental. Finally, we show that carrying out a SC-1 treatment preliminary to Si 3 N 4 capping layer deposition enables the fabrication of Si 3 N 4 gratings with sub-100 nm width on LiNbO 3 thin films.