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UV Characteristics and Performance as Positive-Working Deep, Mid, and Near UV Resists of Phenyl Isopropenyl Ketone Copolymers

Phenyl isopropenyl ketone (PIPK) was copolymerized with styrene and methyl methacrylate (MMA). UV characteristics, resist sensitivity, and durability against O2 reactive ion etching (RIE) were studied on copolymers containing various amounts of PIPK. The copolymers had stronger absorption in the deep, mid, and near UV region and fairly large quantum yield for main chain scission of 0.19–0.37. Both sensitivity and O2 RIE durability increased at the same time as PIPK content in the MMA copolymer increased, though sensitivity and dry-etching durability of positive-working resists are generally in a trade-off relationship. The sensitivities obtained with the MMA copolymer containing 35 mol% of PIPK were 250 mJ cm−2 at 313 nm and 390 mJ cm−2 at 365 nm. The sensitivity at 254 nm was the highest at the PIPK content of 16 mol% and 810 times as high as that of PMMA, but bleaching characteristics were insufficient at this wavelength.