Novel Star Polymers as Chemically Amplified Positive-Tone Photoresists for KrF Lithography Applications

Xanthate-mediated reversible addition–fragmentation chain transfer (RAFT) methodologies have been applicable to preparation of branched or star polymers. In this article, novel star copolymers have been synthesized through xanthate-mediated RAFT polymerization with p-acetoxystyrene and tert-butyl acrylate. Fourier transfer infrared, nuclear magnetic resonance spectra, and gas chromatography analyses indicated that the polymerization was successful between both of the monomers and the star RAFT agent. The intrinsic viscosity and Zimm branching factor (g′) were used to confirm the copolymers’ architecture. The ultraviolet absorbance of the copolymer solutions indicated that the copolymer was suitable for use as a krypton fluoride (KrF) laser photoresist. Moreover, the photolithography performance of the positive-tone chemically amplified photoresist was evaluated. The results indicated that the photosensitive based on the star copolymer was higher than the linear one, and the pattern resolution was around 200 nm at a low exposure energy.