New concept of positive photosensitive polyimide: Reaction development patterning (RDP)

A soluble multiblock copolyimide without specific functional groups such as OH and COOH was prepared by a direct one-pot polycondensation of two types of dianhydrides and diamines in the presence of gamma -valerolactone/pyrid ine catalyst using N-methylpyrrolidone (NMP)/toluene mixture as a solvent. The polyimide film containing the photosensitive agent diazonaphthoquinone (DNQ) compound gave positive-tone behavior by UV irradiation, followed by d evelopment in a mixture of ethanolamine/NMP/H2O (1/1/1 by weight). The scan ning electron microscopic photograph of the resultant image showed fine pat terns with about 20 mum film thickness. Its pattern forming was based on th e photorearrangement of diazonaphthoquinone, a process in which the ring-op ening reaction of imide units of the polyimide with the amine used as a dev eloper and the following degradation of the polymer are induced. Such a new imaging technique combines principles of photolithography and etching of a polyimide to give, what we call, reaction development patterning in which the main chemical reactions directly related to the pattern formation occur during development. (C) 2001 John Wiley & Sons, Inc.