Patterning Behavior of RAFT-Derived 3-Arm Star Terpolymers

The uniformity of polymer matrices can strongly influence pattern retention during negative-tone development. In this study, two 3-arm star terpolymers, designated HTM Random and HTM Block, were synthesized via reversible addition–fragmentation chain transfer polymerization using simultaneous and sequential monomer-addition strategies, respectively. Both polymers were prepared using the same nominal feed ratio of 2-hydroxyethyl methacrylate, dicyclopentanyl methacrylate, and 2-methyl-2-adamantyl methacrylate. Although the two materials exhibited controlled molecular weight distributions and similar FT-IR spectral changes after ultraviolet exposure and post-exposure baking, differences were observed in their chain-packing characteristics, thermal behavior, and developed pattern morphology. The two materials exhibited comparable initial thermal stability but distinct multistep degradation profiles and glass-transition behavior. In contrast, the simultaneous-feed material showed more clearly retained and spatially uniform patterns under the tested development conditions. These results indicate that the materials produced by the two monomer-addition strategies exhibited differences in thermal response and development behavior under the investigated conditions.