DUV resist etch selectivity improvements using UV stabilization

The transition from i-line to DUV (248 nm) processing requires lithography and plasma engineers to address the issue of pattern transfer. The issue of the etch selectivity of DUV photoresists being lower than novolak based i-line photoresists becomes critical at hole and metal levels. Here the selectivity of resist to the substrate are on the order of two or three to one. The traditional approach of just increasing the resist thickness does not become an option as aspect ratios can increase to more than 3.5 for the resist process. A combination of improving the etch selectivity and implementing a stabilization process with DUV resists allows the use of thinner resists. We demonstrate improvements in etch selectivity at the contact level using UV/Bake™ stabilization of the resist films.