Novel polymeric anionic photoacid generators (PAGs) and corresponding polymers for 193 nm lithography

Abstract

A series of new anionic PAGs, as well as PAG-bound polymers designed for use in 193 nm photoresist materials, have been synthesized and characterized. These novel materials provide optical transparency at 193 nm and also good etch resistance. PAG incorporated resists and PAG blended resists were exposed at a wavelength of 193 nm using an ASML 5500/950B optical lithography system with 0.63 NA. Exposed wafers were evaluated using SEM. The fluorine substituted PAG bound polymer and PAG blend resist provided a 110 nm (220 nm pitch) line/space at 11.5, 13.0 mJ cm⁻², and 80 nm isolated features at 3 and 1 mJ cm⁻², respectively. The LER (3σ) results showed that the fluorinated PAG bound polymer has LER values of 6.7 and 6.8 nm for isolated 80 nm and dense 110 nm lines, respectively, while the fluorinated PAG blend resist has LER values of 8.6 and 8.9 nm. The improvement may be due to the direct bonding of PAG into the polymer main-chain, which provides a more uniform distribution, thereby controlling acid diffusion and allowing a higher loading of PAG than the blend sample. The fluorine-free PAG bound or blend resists showed lower photospeed compared to photoresists based on fluorine-substituted PAGs.