Single-Step RIE Fabrication Process of Low Loss InP Waveguide Using CH[sub 4]∕H[sub 2] Chemistry

Single-step C H 4 ∕ H 2 -based reactive ion etching (RIE) process, without alternating O 2 plasma treatment, has been developed with virtually no polymer buildup on the etched surface. InP ridge waveguides up to 1.9 μ m high were etched without any mid- or post-etch O 2 plasma treatment. Smooth and polymer-free sidewalls led to a slight undercut resulting in sidewall slope of ∼ 85 ° . Very low waveguide propagation losses ( 0.28 dB ∕ cm ) of “shallow” etched waveguides were obtained. The etched surface has a root-mean-square roughness of 0.66 nm .