Development of Photosensitive Poly(benzoxazole) Based on a Poly(o-hydroxy amide), a Dissolution Inhibitor, and a Photoacid Generator

Abstract

A positive-type photosensitive poly(benzoxazole) (PSPBO) based on poly(o-hydroxy amide) (PHA), (5-propylsulfonyloxyimino-5H-thiophene-2-ylidene)-(2-methylphenyl)acetonitrile (PTMA) as a photo acid generator (PAG), and 9,9-bis[4-(tert-butoxycarbonylmethyloxy)phenyl]fluorene (TBMPF) as a dissolution inhibitor (DI) has been developed. The TBMPF was synthesized from 9,9-bis(4-hydroxyphenyl)fluorene with tert-butyl bromoacetate. The PSPBO consisting of PHA (74 wt%), TBMPF (22 wt%), and PTMA (4 wt%) showed the high sensitivity of 28 mJ/cm² and high contrast of 2.7 when it was exposed to a 365 nm line (i-line), postbaked at 100 °C for 2 min, and developed with aqueous alkaline developer, 2.38 wt% tetramethylammonium hydroxide solution (TMAHaq) / 5 wt% iso-propanol (iPrOH) at 25 °C. A clear positive image of 3 μm line and space pattern was printed on a film exposed to 50 mJ/cm² of i-line by a contact printing method and converted into the poly(benzoxazole) pattern upon heating at 350 °C for 30 min. This PSPBO showed good thermal and mechanical properties. The value of dielectric constant estimated from the refractive index was 2.82.