Fluoropolymers for 157nm Lithography: Performance of Single Layer Resists

Abstract

Implementation of 157nm lithography using single-layer photoresists will require the development of resists with sufficiently high transparency in the vacuum ultraviolet to permit high resolution imaging using films approximately 200nm thick. One of the more promising approaches to this objective involves the use of fluoropolymers as the base resins in the photoresists, since fluorination decreases the optical absorbance at 157nm. Here we describe the optical properties and imaging performance of two fluoropolymer systems. One system is based upon tetrafluoroethylene copolymers, the other upon vinyl addition copolymers. Both systems incorporate norbornene derivatives to provide aqueous base (developer) solubility and plasma etch resistance.