Metal mask free dry-etching process for integrated optical devices applying highly photostabilized resist.

Photostabilization is a widely used post lithographic resist treatment process, which allows to harden 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 0,3-3.3 μm thick positive resist profiles followed by heat treatment up to 280 °C. 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. This procedure is demonstrated by the results obtained in etching of various integrated optical structures.