Studies on the application of polymeric materials containing thymine photodimer to the electron beam resists.

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Nucleic acid polymers containing thymine photodimer were studied as an electron beam resist material for microlithography. Photochemical reactions of the nucleic acid polymers have been studied and applied as Deep-UV photoresists materials, which gave high resolution pattem. We also found that the nucleic acid polymers can also be applied as electron beam (EB) lithography. One of the nucleic acid polymers is a polycarbonate containing both thymine photodimer and tertiary alcohol units in the polymer main chain. This study deals with preparations of the acid sensitive polymer containing pyrimidine units, and the reaction by electron beam with or without acid generator as an chemical amplified resist.The diol derivative of thymine photodimer were condensed with various diols using carbonyl diimidazole to give both random and altemating polycarbonates. Photolyses of the polycarbonates containing thymine photodimer units were carried out in film state. Thin films were obtained from their solution in organic solvent using spinner, casting on the silicon wafer. Photochemical reaction was followed by UV spectrophotometer at 270 nm which was absorption of the regenerated thymine units by dissociation of the polymer. After prebaking, the fihns were exposed to irradiation of electron beam until complete photochemical reaction.Increase of sensitivity and gamma values in the presence of triphenylsulfonium trifulate in the case of altemating copolycarbonate was observed. In addition to this high sensitivity and high resolution, this polymer can be developed with TMAH alkali solution without swelling.