Optimal plasma etching for fabrication of channel waveguides

We report on a study of the evolution of the surface roughness of polymer films during plasma etching. Effect of plasma etching on sidewall roughness was also studied by fabricating different width waveguides and measuring their loss. The understanding of surface roughness evolution was used to explain the roughness effects observed in sidewalls and strategies to minimize the same have been developed. Fluorinated polyimides were used as candidate materials for this study. Roughness evolution on the top surface of the polyimide films was studied by exposing the film to an oxygen plasma under different conditions. After each run, the amount of material etched was measured and a non-contact AFM scan of the surface was obtained.