Synthesis and micropatterning properties of a novel base-soluble, positive-working, photosensitive polyimide having an o-nitrobenzyl ether group

Authors

  • Gyo Jic Shin,

    1. Polymer Research Institute/Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-Dong, Pohang, 790-784 Korea
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  • Jin Chul Jung,

    Corresponding author
    1. Polymer Research Institute/Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-Dong, Pohang, 790-784 Korea
    • Polymer Research Institute/Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-Dong, Pohang, 790-784 Korea
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  • Jun Ho Chi,

    1. Polymer Research Institute/Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-Dong, Pohang, 790-784 Korea
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  • Tae Hwan Oh,

    1. Department of Chemistry, Korea Advanced Institute of Science and Technology, 373-1, Guseong-Dong Yuseong-Gu, Daejeon, 305-710 Korea
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  • Jin Beak Kim

    1. Department of Chemistry, Korea Advanced Institute of Science and Technology, 373-1, Guseong-Dong Yuseong-Gu, Daejeon, 305-710 Korea
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Abstract

A novel positive-working, photosensitive polyimide, poly[1,4-phenyleneoxy-1,4-phenylene-2,2′-di(2-nitrobenzyloxy)benzophenone-3,3′,4,4′-tetracarboxdiimide] (OPI-Nb), developable with an aqueous base was prepared by the o-nitrobenzylation of a polyimide, poly(1,4-phenyleneoxy-1,4-phenylene-2,2′-dihydroxybenzophenone-3,3′,4,4′-tetracarboxdiimide) (OPI), derived from 2,2′-dihydroxy-3,3′,4,4′-benzophenonetetracarboxylic dianhydride (DHBA) and 4,4′-oxydianiline, and it micropatterning properties were investigated. The o-nitrobenzylation of OPI to OPI-Nb was conducted with o-nitrobenzyl bromide in N-methyl-2-pyrrolidinone containing Et3N. The DHBA monomer was synthesized by exhaustive KMnO4 oxidation of bis(2-dimethoxy-3,4-dimethylphenyl)methane obtained by etherification of bis(2-hydroxy-3,4-dimethylphenyl)methane with iodomethane, followed by deprotection of the methoxy groups and cyclodehydration of the obtained 2,2′-dihydroxy-3,3′4,4′-benzophenonetetracarboxylic acid. The intermediate bis(2-hydroxy-3,4-dimethylphenyl)methane was prepared by the condensation of 2,3-dimethylphenol with paraformaldehyde. The degree of o-nitrobenzylation was determined to be over 94 mol % from 1H NMR absorption of benzylic CH2 protons. The aromatic OPI was perfectly soluble in a dilute aqueous NaOH solution and tetramethylammonium hydroxide (TMAH), whereas OPI-Nb was not even swellable in them. In the micropatterning process, OPI-Nb showed a line-width resolution of 0.4-μm and a sensitivity of 5.4 J/cm2 when its thin films were irradiated with 365-nm light and developed with a 2.38% aqueous TMAH solution at room temperature for 90 s. The thickness loss of OPI-Nb films measured after postbaking at 350 °C was in the 8–9% range. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 776–788, 2007

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