Single-layer chemically amplified photoresists for 193-nm lithography

Abstract

Recent advances in ArF excimer laser exposure tools have led to a search for new resist materials for use at 193 nm. To date much of this effort has been directed toward surface imaged or bilayer resist schemes and only recently have there been reports of single layer systems with sufficient transparency for use at this short wavelength. We will describe our approach to a 193 nm single layer resist system based on methacrylate terpolymers. A terpolymer system based on tert-butylmethacrylate, methyl methacrylate and methacrylic acid developed for laser direct imaging applications has been adapted for high resolution imaging by modifying the terpolymer composition and by optimizing the photoacid generator loading. This resist is useful for the characterization of new exposure systems and we will describe imaging results on a prototype 0.50-NA step and scan system. We will also describe the effect photoacid structure has on the imaging properties of the resist and compare the efficiency of deprotection chemistry at 193 and 248 nm. In addition, we will discuss modifications of the aliphatic polymer described above by replacement of the ‘‘inert’’ methyl methacrylate monomer by monomers containing alicyclic substituents to improve the resistance to reactive ion etching.