Deep anisotropic LiNbO3 etching with SF6/Ar inductively coupled plasmas

A SF6/Ar inductively coupled plasma (ICP) technique was investigated to improve etching of proton exchanged LiNbO3. The influences of He backside cooling, power, and gas flows on characteristics such as etching rate, sidewall slope angle, and surface roughness were investigated. Total gas flow is a key parameter that affects etching results, and an optimized gas flow (50 sccm) was used for lengthy etching processes (30 min). Deep (>3 μm) and highly anisotropic etching, as well as ultra smooth LiNbO3 surfaces were achieved in a single-step run. The authors’ proposed method has achieved the deepest, most vertical, minimal residue structure yet reported for single-step ICP etching.