Synthesis and evaluation of positive‐acting photosensitive polyimides with phenol moiety

Novel positive‐acting photosensitive polyimide resists (1) developable with an alkaline aqueous solution were prepared. The resists consisted of a naphthoquinone diazide (NQ) and a polyamic acid bearing hydroxyphenyl groups (PA). The hydroxyphenyl moieties are newly incorporated by adding 2‐N,N‐dimethylaminoethyl‐3‐hydroxybenzoate (m‐PEA) or 2‐N,N‐dimethylaminoethyl‐4‐hydroxybenzoate (p‐PEA) to the polyamic acid, through ionic interaction between the carboxylic acid and the amine. The NQ acts as a solution inhibitor for the PA by the interaction with the hydroxyphenyl moiety. This system is similar to that of phenol‐novolac resin/NQ resists currently conducted in the fabrication of the Large Scale Integrated circuit (LSI). The resist (1) is exposed to a G‐line and is developed with tetramethylammonium hydroxide aqueous solution to provide fine patterns, proving that the (1) is compatible with LSI‐production lines currently applied. A novel polyamic acid‐curing mechanism found in the course of this study is also reported.