Design Concepts of Single-Layer Resists for Vacuum Ultraviolet Lithography

Abstract

We investigated the possible use of single-layer resists in vacuum ultraviolet (VUV) lithography. The transmittances in the VUV region of commonly used polymers for photoresists were almost the same. These values were about 20% at 157 nm per 1000 Å-thickness at most. The transmittance at 157 nm of a poly ( p -hydroxystyrene) (PHS)-type polymer was slightly increased by halogenation of the aromatic group. Negative working behavior was observed for PHS-type resists. It is thought that both crosslinking and deprotection occurred in PHS-type polymers. A methacrylate-type resist showed high contrast due to the photodecomposition of the base polymer and photo-deprotection in addition to acidic deprotection. It was estimated that the resolution capability of this resist was 80 nm lines and spaces (L/S) (λ157 nm, NA 0.65) using a PROLITH/3D lithography simulator with experimental dissolution data.