Photoresist materials comprising photobase generators and epoxy resins bearing carboxylic acids to lead to marked enhancement of base-catalyzed cross-linking reactions

Most of the photopatterning materials based on epoxy resins utilize photoacid generators (PAGs), which generate superacids as catalysts. They have been used for high aspect ratio photoresists in the fabrication of MEMS devices. However, there is a drawback, in that the acidic species from PAGs will induce metal corrosion. One of the approaches to overcome this problem is the use of photobase generators (PBGs) because organic bases would induce no corrosion. Although there have been many previous investigations of PBGs, only a few articles have mentioned photoreactive materials relying on PBGs because of their low photosensitivity. We report here highly sensitive photopatterning materials comprising PBGs and an epoxy resin bearing carboxylic acid groups. As a result, the photopatterning materials showed higher photosensitivity than conventional epoxy resin systems. We obtained high-photosensitivity (up to 900 mJ/cm²), high-resolution (10-μm line-and-space) patterning materials in films, 10 μm in thickness.