Development of Photosensitive Porous Polyimide with Low Dielectric Constant.

Abstract

A negative-working photosensitive porous polyimide (PS-P-PI)-precursor based on a poly(amic acid) (PAA), 1, 4-dihydropyridine derivatives (DHP)s and poly(ethylene glycol) (PEG) as a porogenic agent has been developed. The PAA was prepared by ring-opening polyaddition of 3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA). The PS-P-PI-precursor film consisting of PAA, DHPs and PEG was prepared. The dissolution behavior of the phase separated polymer film after exposure and post exposure bake (PEB) was studied. It was found that the extraction of PEG by supercritical fluid (SCF) was effective to get a high dissolution contrast. The extraction of PEG has also provided the PS-P-PI-precursor which has submicron scale micropores. The PS-P-PI-precursor was converted to the corresponding PS-P-PI by thermal treatment at 380°C. The PS-P-PI system was capable to resolve a 20μm line and space pattern when a 10μm-thick film was used. The dielectric constant of the PS-P-PI film was 2.0 at 1MHz. High propagation efficiency was obtained when the PS-P-PI pattern film was used as an insulation layer.