Enhanced Lithographic Performance of Polymer-Bound PAG Photoresists Synthesized via RAFT Polymerization

Photoacid generators (PAGs) play an important role in chemically amplified resists (CARs), but small molecule PAGs have low solubility and limited compatibility with resins, which may lead to various problems. One of the important solutions is to bound PAG to polymer chains but differences in monomer reactivity can lead to an uneven distribution of molecular chain sequences between different polymer chains during polymerization, potentially impacting the lithographic performance. In this work, PAG units were incorporated into the photoresist resin polymer backbone via reversible addition-fragmentation chain transfer (RAFT) polymerization to synthesize methyl methacrylate polymer with different PAG loadings. The lithographic properties of the PAG bound polymer resist and the PAG blend polymer resist were studied and compared. The direct incorporation of PAG functionality into the polymer showed lower sensitivity, shorter acid diffusion length, and better compatibility. By observing the lithography results through AFM and SEM, the lithography lines of the PAG bound polymer photoresist synthesized via RAFT polymerization exhibited improved morphology and narrower line edge roughness (LER).