ABSTRACT:A novel negative-working thermally stable photosensitive polymer based on poly(naphthylene ether), a cross-linker hexa(methoxymethyl)melamine, and a photoacid generator (5-propylsulfonyl-oxyimino-5H-thiophen-2-ylidene)-(2-methylphenyl)acetonitrile. Poly(naphthylene ether) was prepared via the oxidative coupling polymerization of 4,4 0 -bis(1-naphthyloxy)-2,2 0 -dimethylbiphenyl. This photosensitive polymer showed a high sensitivity (D 0:5 ) of 6.0 mJ cm À2 and a high contrast ( 0:5 ) of 5.2, when it was exposed to a 436 nm light, post-exposure baked at 140 C for 5 min, and developed with toluene.