Synthesis and characterization of negative‐type polyamic acid ester with 1‐methacryloyloxy‐2‐propanoate group

Abstract A negative‐type photosensitive polyamic acid (PAA) was synthesized from cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride and 2‐(methacryloyloxy)ethyl 3,5‐diaminobenzoate in N ‐methyl‐2‐pyrrolidinone. Glycidyl methacrylate was added into the PAA solution to yield a photosensitive PAA ester (PAE) by the ring‐opening esterification reaction of the carboxylic acid group in the PAA and glycidyl methacrylate. Esterification reactions were conducted with varying reaction temperatures and times. The typical PAE (PAE‐C3) with a degree of esterification of 20% was used for a photosensitivity study. We investigated the effects of the postexposure baking temperature, amount of photoinitiator, and exposure dose on the photosensitivity of PAE‐C3. Furthermore, a photolithography evaluation was conducted on PAE‐C3 in the presence of 1‐[4‐(phenylthio)phenyl]‐2‐( O ‐benzoyloxime)‐1,2‐octanedione as a photoinitiator using a mercury lamp at a 365‐nm wavelength. The resolution of the film with 2.0‐μm thickness was about 8 μm. PAE‐C3 cured at 250°C for 60 min was stable up to around 310°C in a nitrogen atmosphere. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2252–2258, 2006