Synthesis and Characterizations of Positive-Working Photosensitive Polyimides Having 4,5-Dimethoxy-o-Nitrobenzyl Side Group

Abstract

To synthesize a new positive-working photosensitive polyimide, alkali-soluble polyimide containing carboxylic acid side group was synthesized, and parts of its carboxylic acid groups were esterified with 4,5-dimethoxy-2-nitrobenzyl bromide. The chemical structure of the resulting polymer was characterized by 1 H-NMR and FT-IR spectroscopies. The substitution ratio of photosensitive groups was estimated by 1 H-NMR integration values, and the thermal properties were examined by differential scanning calorimetry and thermogravimetric analyses. Upon UV irradiaition, 4,5-dimethoxy-2-nitrobenzyl moiety underwent the photodegradation with generation of carboxylic acid side groups as evidenced by UV/vis spectroscopy. As a result, the polymer became soluble in alkaline developer, and a micron-sized positive pattern was successfully fabricated from the synthesized polymer.