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ROGER H. FRENCH, JERALD FELDMAN, FREDRICK C. ZUMSTEG, MICHAEL K. CRAWFORD,
ANDREW E. FEIRING, VIACHESLAV A. PETROV, FRANK L. SCHADT III & ROBERT C. WHELAND,
DuPont Co., iTechnologies and Central Research and Development, Wilmington, DE, USA
JOSEPH GORDON & EDWARD ZHANG, DuPont Photomasks Inc., Danbury, CT, USA

ABSTRACT

Substantial progress has been made in developing novel fluoropolymer materials for 157nm lithography. Materials with sufficient transparency at 157 nm to enable both thick single layer resists and high transmission pellicle membranes have been demonstrated. We have shown that tetrafluoroethylene (TFE)-containing 157 nm photoresist binder resins can be made that are sufficiently transparent to be used at film thickness greater than 200nm, have good photosensitivity, exhibit low outgassing upon exposure, are compatible with aqueous base development, and have etch rates comparable to PHOST resins. Optical absorbance on the order of 1.5/μm @ 157 nm should be possible for photoresits. We have now demonstrated sub- 100nm 1:1 imaging in thick TFE-containing photoresits which have optical absobance coefficients of 1.75/mm and thickness greater than 200nm. In addition, features as small as 50 nm have been imaged in a 168 nm thick film of TFE containing photoresist. Further improvements in optical transparency and high resolution imaging are anticipated using fluoropolymers, and in particular TFE-based resins. In addition, a number of families of fluoropolymers have been developed which meet the transparenct guidelines for pellicles. Some of these materials have now been optimized to allow unsupported membrane formation and 95% transmission, even though lifetime continues as an issue. Significant progress has been made toward 157nm lithography a ralisitic industry option in the context of the ITRS roadmap.