Synthesis and characterization of aqueous base developable negative-tone poly(imide-amic acid) copolymers by the effect of the imidization ratio

Abstract

Negative-tone photosensitive poly(imide-amic acid) (PIA) copolymers were synthesized from a chemical imidization process using poly(amic acid) that was prepared from a polycondensation reaction of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 4,4′-oxydianiline (ODA), and di[2-(methacryloyloxy)ethyl]-5-aminoisophthalate (Di-HEMA-AP) with photoreactive acrylate groups. The imidization ratio was controlled by the reaction time, and the synthesized PIA copolymers were investigated using spectroscopic methods. The photolithographic behaviors of the formulations composed of PAA and PIA copolymers, Michler’s Ketone (MK), and crosslinker were evaluated using a 2.38 wt. % tetramethylammonium hydroxide (TMAH) solution. The solubility decreased with increasing imidization ratio in an alkaline base solution because of the reducing content of carboxylic acid groups in the polymer main chain. The formulations from PIA copolymers gave clear patterns without distortion by UV light i-line irradiation and followed 2.38 wt. % TMAH solution development.