Negative-type Chemically Amplified Photosensitive Novolac

A negative-type chemically amplified photosensitive resist based on a novolac resin, 4,4'-methylenebis[2,6-bis(methoxymethyl)phenol] (MBMP) as a cross-linker, and (5-propylsulfonyloxyimino-5H-thiophen-2-ylidene)-(2-methylphenyl)acetonitrile (PTMA) as a photoacid generator has been developed. This resist showed the high sensitivity (D0.5) of 5.3 mJ/cm2 and good contrast (γ0.5) of 3.5 after exposure of 365 nm UV light, post exposure baked at 110 ° for 5 min, and developed with 2.38 wt% tetramethylammonium hydroxide aqueous solution. The 20 μm image was made in the polymer with 12 μm film thickness by using the resist consisting of novolac resin (90 wt %), MBMP (7 wt %), and PTMA (3 wt %).