Alkali-Developable Positive-Photosensitive Polyimide Based on Diazonaphthoquinone Sensitizer

We report on the positive alkali-developable photosensitive polyimides based on an alkali-soluble polyimide precursor as a base polymer and diazonaphthoquinone (DNQ) sensitizer to improve process stability and sensitivity. Polyamic acid ester with pendant carboxylic acid (PAE-COOH) showed good dissolution behavior in aqueous alkali developer. The dissolution rate of PAE-COOH was controlled by the content of pendant carboxylic acid. It was found that a photosensitive system composed of butyl ester of PAE-COOH and a DNQ compound can avoid the residue at the edge of hole patterns (footing) after development, while that of methyl ester of PAE-COOH showed the residue. A DNQ compound containing sulfonamide derived from diaminodiphenylether renders improved sensitivity compared with DNQ compounds derived from phenol derivatives.