Development of high-performance negative-tone resists for 193-nm lithography

Abstract

We have been developing negative-tone resist systems utilizing an acid-catalyzed intramolecular esterification of γ-and δ-hydroxy acid for ArF phase-shifting lithography. In this paper, α−acryloyloxy-β,β-dimethyl-γ-butyrolactone (DBLA), adamantane lactone acrylate (AdLA), and norbornane lactone acrylate (NLA) were examined as a precursor of hydroxy acid. It was found that AdLA and NLA are not hydrolyzed into hydroxy acid under an alkali hydrolysis condition. DBLA was found to produce γ-hydroxy acid, which is stable in the resist solution. The γ-hydroxy acid derived from DBLA becomes γ-lactone relatively easily by an acid-catalyzed reaction and can be used to make resists insoluble.Since the variation and the flexibility of the copolymer composition of the base polymer can be increased, the resist properties are controllable and the pattern quality can be improved by utilizing γ-hydroxy acid derived from DBLA.