Synthesis and characterization of a positive-working, aqueous-base-developable photosensitive polyimide precursor

A positive-working, aqueous-base-developable photosensitive polyimide precursor based on poly(amic ester)-bearing phenolic hydroxyl groups and a diazonaphthoquinone photosensitive compound was developed. The poly(amic ester) was prepared from a direct polymerization of 2,2'-bis-(3-amino-4-hydroxyphenyl)hexafluoropropane and bis(n-butyl)ester of pyromellitic acid in the presence of phenylphosphonic dichloride as an activator. Subsequently, the thermal imidization of the poly(amic ester) precursor at 300degreesC produced the corresponding polyimide. The inherent viscosity of the precursor polymer was 0.23 dL/g. The cyclized polyimide showed a glass-transition temperature at 356degreesC and a 5% weight loss at 474degreesC in nitrogen. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared spectroscopy and H-1-NMR. The photosensitive polyimide precursor containing 25 wt % diazonaphthoqrone, photoactive compound showed a sensitivity of 150 mJ/cm(2) and a contrast of 1.65 in a 3 mum film with 1.25 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 10 gm was obtained from this composition. (C) 2002 Wiley Periodicals, Inc.