Modified Polymer Architecture for Immersion Lithography

摘要

In the past several years, ArF immersion lithography has been developed rapidly for practical applications. ArF immersion lithography is now researched actively and developed for the purpose of implementing the 45-nm technology node. For the device designs involved immersion lithography, line width roughness (LWR) and film wettability are very important criteria to control in the point of high resolution and defectivity. Free radical polymerization in the presence of thiocarbonylthio compounds of general structure Z-C(=S)S-R provides living polymers of predetermined molecular weight and narrow molecular weight distribution by a process of reversible addition-fragmentation chain transfer (RAFT). A rationale for selecting the most appropriate thiocarbonylthio compounds for a particular monomer type is presented with reference to the polymerization of methacrylates, styrenes, acrylates, acrylamides, and vinyl acetate. In this study, resist polymers with narrow polydispersity (PD) and controlled molecular structure were prepared using controlled radical polymerization techniques, such as RAFT polymerization. PD index of polymers showed between about 1.2 to 1.4 and in some instances, between about 1.1 to 1.2 or less. Additionally, each polymer chain has a RAFT end group. That is the resulting polymer contains a chain transfer agent (CTA) moiety at each terminal end of polymer backbone. It is possible that hydrophobic CTAs can be used to decrease the hydrophilicity of resist film.