Novel positive‐type photosensitive polyimide with low dielectric constant

Abstract

AbstractA novel positive‐type photosensitive polyimide (PSPI) with a low dielectric constant was developed. The PSPI system was composed of soluble block PI (Bco‐PI) with a hydroxy group and diazonaphthoquinone as a photoreactive compound. The base Bco‐PI was prepared by a direct one‐pot polycondensation of 2,2‐bis(3‐amino‐4‐hydroxy‐phenylhexafluoropropane), 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane, and cyclohexanetetracarboxylic dianhydride in the presence of a γ‐valerolactone and pyridine catalyst system using N‐methyl‐2‐pyrrolidone as the solvent. The film of Bco‐PI was colorless and transparent, both important factors for a PSPI. Photosensitive soluble block PI (Bco‐PI), containing 20 wt % ester of 2,3,4‐trihydroxybenzophenone with 1,2‐naphthoquinone‐(2)‐diazide‐5‐sulfonic acid (NT200), showed a sensitivity of 350 mJ/cm2 and a contrast of 1.20 when it was exposed to UV light, followed by development with 5% tetramethylammonium hydroxide aqueous solution at room temperature. The estimated optical dielectric constants of the PIs with and without NT200 were 2.68 and 2.75, respectively. These values were significantly lower than those of conventional aromatic PIs, such as Kapton film (50EN). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 15–21, 2005