Novel fluoropolymers for use in 157 nm lithography

Unexpectedly good UV transmittance at 157 nm of poly(norbornene sulfone) bearing a pendant hexafluoroisopropanol functionality has prompted us to employ this fluoroalcohol as an acid group for the design of chemical amplification resists for use in 157 nm lithography. The backbone structures to which the hexafluoroalcohol group is attached are polynorbomene and polystyrene. Furthermore, our discovery that poly(methyl α-trifluoromethylacrylate) is adequately transparent at 157 nm has led us to incorporate the α-trifluoromethylacrylic unit in the polymer backbone by radical copolymerization with styrenes and norbornenes. Thus, four platforms are currently available to us in preparation of 157 nm resist polymers; 1) all-acrylic, 2) all-norbornene, 3) acrylic-norbornene, and 4) acrylic-styrenic systems.