Synthesis of 3-(t-Butoxycarbonyl)-N-vinyllactams and application of their polymers as chemical amplification resists

Abstract

Most of positive chemical amplification resists do not have enough stability to process delay. It has been claimed that airborne contaminations neutralize acids from photoacid generators. Our new environmentally stable chemical amplification positive resist has been designed using polymer-bound basic moiety in order to reduce migration of the photogenerated acid throughout the process. Poly(3-(t-butoxycarbonyl)-1-vinyl-2-pyrrolidinone), poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam), poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam-co-t-butyl acrylate), poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam-co-t-butyl methacrylate) and poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam-co-t-butyl acrylate-co-hydroxystyrene) were synthesized and evaluated as potential deep UV photoresists. The synthesized polymers have excellent transmittance at 248 nm(absorbance=0.018~$0.041㎛^{-1}$). In addition, the synthesized polymers possess good thermal stability up to 200℃ and high glass transition temperatures(140~195℃). And post-exposure delay(PED) stability were examined on the synthesized polymer resist systems. The lowering of resist sensitivity with increasing 3-(t-butoxycarbonyl)-1-vinylcaprolactam(BCVC) content of resist copolymers shows that the BCVC units trap of photogenerated acids. The contrast of this resist was not deteriorated with the PED time. We obtained 0.2㎛ line/space patterns. The pattern profile is not deteriorated and T-top is not observed with 2 h PED time. By introducing basic units into a matrix polymer, this new resist system can prevent basic additives from migrating to the surface. Especially, it is interesting that exposed area of poly(3-(t-butoxycarbonyl)-1- vinyl-2-pyrrolidinone) resist can be developable by pure water after deblocked by photogenerated acid. we knew that the new resist system has desirable properties such as high transparency in deep UV region, facile deprotection, and proper sensitivity. And we confirmed improvement of environmental stabili...