Styrylmethylsulfonamides: Versatile base-solubilizing components of photoresist resins

A series of styrylmethylsulfonamides have been prepared and used as components of chemically amplified deep-UV photoresists based upon the acid catalysed removal of t-butoxycarbonyloxy (t-Boc) groups. The sulfonamide group is similar in acidity to the phenolic moiety commonly used in resists, but offers the advantages of much lower optical absorption and substantial resistance to chemical degradation. Reaction of p-chloromethylstyrene with N-acetyl methanesulfonamide, followed by removal of the N-acetyl group, yielded 4-amido-sulfonylmethylstyrene (3). The reaction of 4-bromo-benzylsulfonyl chloride with methylamine, followed by replacement of the bromide with ethylene by means of the Heck reaction, yielded N-[(4-ethenylphenyl)methyl]-sulfonamide (4). Polymerization of 3 or 4 with t-butoxycarbonyloxystyrene (TBS) yielded polymers with low optical density but having low glass transition temperatures (Tg). Polymerization of 3, TBS and SO2 yielded terpolymers of higher Tg (>130 degrees C) which could be imaged with sub 0.30 mu m resolution using a conventional photoacid generator such as 2-nitro-6-trifluoromethyl-benzenesulfonate. The terpolymers have good post-exposure bake stability without the need for a protective overcoat, and are attractive new materials for deep-UV lithography at 248 nm.