Direct patterning of poly(ether ether sulfone) using a cross-linker and a photoacid generator

A negative-type photosensitive poly(ether ether sulfone) (PSPEES) based on a commercially available engineering plastic poly(oxybiphenyl-4,4'-diyloxy-1,4-phenylenesulfonyl-1,4-phenylene) (PEES), a cross-linker 4,4'-methylenebis[2,6-bis(methoxymethyl)phenol] (MBMP) having good compatibility with PEES, and diphenylidonium 9,10-dimethoxyanthracene-2-sulfonate (DIAS) as a photoacid generator (PAG) has been developed. The resist consisting of PEES (85 wt %), MBMP (10 wt %) and DIAS (5 wt %) showed a high sensitivity (D-0.5) of 21 mJ/cm(2) and a contrast (gamma(0.5)) of 2.1 when it was exposed to i-line (365 nm wavelength light), post-exposure baked (PEB) at 170 degrees C for 3min, and developed with N,N-dimethylacetamide (DMAc) at room temperature. A fine negative-image featuring 4 mu m line-and-space pattern was obtained on the film. Thus, this photolithographic system has a highly potential to be utilized in the industry for next generation, because most of engineering plastics having aromatic ring are available as matrix polymers, and this process is not necessary high thermal curing treatment after development.