Carbon-rich cyclopolymers: Their synthesis, etch resistance, and application to 193 nm microlithography

We describe a cyclopolymerization approach to novel cyclic materials incorporating a) etch-stable adamantyl esters and b) t-butyl esters as functionalities suitable for chemical amplification. The synthesis of the monomers follows a highly convergent approach from the readily synthesized 1-adamantyl malonate ester. Two polymerizable side chains are then added, incorporating either a) t-butyl acrylate esters, or b) a terminal olefin functionality. These bifunctional, carbon-rich monomers undergo smooth and efficient free radical ring-closing cyclopolymerization to afford soluble, processable polymers that do not contain residual olefinic signals. In order to optimize the lithographic performance of the materials, these crystalline monomers can also be copolymerized with maleic anhydride, or other desirable monomers. These resists show excellent transparency at 193 nm (A<0.3/μ) and outstanding etch resistance. When used in combination with a photoacid generator, they can be used to formulate deep UV, chemically amplified photoresists. Preliminary imaging experiments conducted with a 193 nm ArF laser stepper exposure unit demonstrate features below 0.18 μ.