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Photolithography at 157 nm requires development of new photoresists that are highly transparent at this wavelength. Transparent fluoropolymer platforms have been identified which also possess other materials properties required for chemically amplified imaging and aqueous development. Polymers of tetrafluoroethylene (TFE), a fluoroalcohol-substituted norbornene and an acid-labile acrylate ester show the best combination of properties. A solution, semibatch, free-radical polymerization process was developed allowing synthesis of the terpolymers on a multikilogram scale. Further property enhancements may arise from replacing the norbornene with functionalized tricyclononenes. Formulated resists have been imaged in a 157 nm microstepper. #

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The design ofan organic material satisfying all ofthe requirements for a single layer photolithography resist at 157 nm is a formidable challenge. All known resists used for optical lithography at 193 nm or longer wavelengths are too highly absorbing at 157 nm to be used at film thicknesses greater than -9O nm. Our goal has been to identify potential, new photoresist platforms that have good transparency at 157 nm (thickness normalized absorbance of2.5 rim' or less), acceptable plasma etch resistance, high Tg, and compatibility with conventional 0.26 N tetramethylammonium hydroxide developers. We have been investigating partially fluorinated resins and copolymers containing transparent acidic groups as potential 157 nm photoresist binders; a variety ofmaterials with promising initial sets ofproperties (transparency, etch resistance, solubility in aqueous TMAH) have been identified. Balancing these properties with imaging performance, however, remains a significant challenge.