A polymeric photobase generator containing oxime-urethane groups: Crosslinking reaction and application to negative photoresist

A polymeric photobase generator containing oxime-urethane groups was prepared by copolymerization of methyl methacrylate and methacryloxyethyl benzophenoneoxime urethane, and its photo and thermal crosslinking reaction after irradiation was examined from the measurement of UV and IR absorption spectral changes, insoluble fraction, and molecular weight changes. The photo-crosslinking reaction of the copolymer film was more efficient when irradiations were carried out with 310 nm UV light in the presence of benzophenone than with 254 nm UV light without the addition of benzophenone. The crosslinking reaction increased after postexposure baking (PEB), and this thermal crosslinking reaction mechanism was studied from the identification of the photolysis products of a model compound, benzophenoneoxime phenylurethane, by a high-performance liquid chromatography. The results indicate that the thermal crosslinking reaction of the copolymer after PEB is due to the formation of urea-type chemical bonds. Resist properties of the copolymer were examined from the measurement of normalized thickness and micropattern development. A negative tone image with a resolution of 2 mum was obtained with this copolymer, having a sensitivity (D-c(0.5)) of 1200 mJ/cm(2) and contrast (gamma(n)) of 1.31, when irradiation was carried out with 310 nm UV light in the presence of benzophenone following chloroform development. (C) 2004 Wiley Periodicals, Inc.