Optimized Deep UV hardbake process for metal-free dry-etching of integrated optical devices

Photostabilization is a widely used post lithographic resist treatment process, which allows hardening the resist profile in order to maintain critical dimensions and to increase selectivity in subsequent process steps such as reactive ion etching. In this paper we present the optimization of Deep UV-curing of 0,3-3.5 μm thick positive resist profiles followed by heat treatment up to 280 0C. The effectiveness of this resist treatment allows for metal mask free reactive ion etching with selectivity up to 6 for silicon structures, thermal silicon oxide and silicon oxynitride. A number of experimental results on integrated optics structures are presented that demonstrate the improved etch profiles obtained with this approach.