Optimized Deep UV Curing Process for Metal-Free Dry-Etching of Critical Integrated Optical Devices

In this paper we present results of Deep UV-curing of resist followed by thermal treatment at temperatures up to 280°C. The curing process was optimized for positive resist profiles of Fujifilm with thicknesses from 0.3 to 3.0 µm. The procedure was for the first time employed to etch critical optical structures in silicon oxynitride. Furthermore, the effect of this resist treatment on the geometry and quality of the etched profiles in silicon, silicon oxide, silicon nitride, and silicon oxynitride, having dimensions as typically applied in integrated optical devices, was studied. Channel waveguides with steep and smooth sidewalls were realized, without usage of a metal hard mask which would reduce the optical performance, at high etch selectivity (up to 6) for the materials under investigation. The reliable fabrication of various integrated optical structures with critical dimensions, like sub-micron gaps between adjacent waveguide channels, was demonstrated.