Fabrication of silicon microring resonator with smooth sidewalls

Fabrication of silicon microring resonators was optimized by using electron-beam lithography (EBL) and inductively coupled plasma (ICP) etching with different mask materials. Sidewall roughness of less than 10 nm was revealed by high-resolution scanning electron microscopy (SEM) without any post-etch process. The fabrication processes are described in detail, and comparisons are made in consideration of process complexity, process latitude, and sidewall roughness.