Haruhiko Kikkawa

Photosensitive Polyamic Acids Developable with Aqueous Alkaline Solutions

New negative-type photosensitive polyamic acids, precursors of polyimides, developable with aqueous alkaline solutions were synthesized. Among diamine monomers having a photofunctional group, 2′-(methacryloyloxy)ethyl 3,5-diaminobenzoate yields high molecular weight polyamic acids. A photosensitive polymer composition consisting of Michlers ketone and a thermally stable peroxide, 3,3′,4,4′-tetrakis(t-butyldioxycarbonyl)-benzophenone, results in high photosensitivity. The photosensitive coating of the composition is soluble in aqueous alkaline solutions as well as in organic aprotic polar solvents and either can be used as a developer of the coating. However, resolution of the patterns is quite different especially with thick films. Solvent developers result in poor resolution whereas aqueous alkaline developers give patterns of high aspect ratio even with thick films. This is probably due to the difference in the diffusion efficiency and swelling property of the polymer to the developers. Effects of copolymerizing with an ordinary diamine monomer on photosensitivities and film properties of the polyimides derived from their precursors are also discussed.