Preparation of acid‐cleavable branched polymers for argon fluoride photoresists via reversible addition–fragmentation chain‐transfer polymerization

Abstract

A series of branched polymers for chemically amplified resists (CARs) were prepared through the reversible addition–fragmentation chain‐transfer (RAFT) copolymerization of three monomers with lithographic functionalities and an acid‐cleavable dimethacrylate monomer. The three monomers with lithographic functionalities were 2‐ethyl‐2‐adamantyl methacrylate, α‐γ‐butyrolactone methacrylate, and 3‐hydroxy‐1‐adamantyl methacrylate. The acid‐cleavable monomer was 2,5‐dimethyl‐2,5‐hexanediol dimethacrylate (DMHDMA), and 2‐cyanoprop‐2‐yl‐1‐dithionaphthalate was used as a chain‐transfer agent. Because DMHDMA contains two methacrylate groups, it induced the branched structures of the polymers. The degree of branching could be controlled by the molar fraction of DMHDMA in the monomer mixtures. The size and structure of the polymers obtained after hydrolysis were very close to those of linear polymers prepared by RAFT copolymerization with the same amount of reagents, only without the acid‐cleavable monomer. A preliminary lithography test using an argon fluoride source demonstrated that the acid‐cleavable branched polymers could be promising candidates for CAR materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

ArF photoresist polymers with nitrogen or sulfone moieties for negative tone development process

“…In addition to the monomer composition of polymers, lithographic performance of photoresists is affected by several factors including the formulation of the photoresists. 1,6,10,11 Since we applied the same formulation of photoresists with conventional Ref2 polymer to the photoresists with PAM1, the improvement of lithographic performance will be observed when the optimum formulation is determined.…”

Synthesis of Narrow Molecular Weight Distribution Copolymers for ArF Photoresist Materials by Nitroxide Mediated Polymerization

“…CRP however does not require the stringent purification procedure and conditions required of ionic polymerizations. Consequently, two CRP techniques, such as atom transfer radical polymerization (ATRP) and reversible addition fragmentation chain transfer (RAFT), have been used to synthesize well‐defined statistical methacrylate‐based copolymers with narrow molecular weight distribution for ArF lithography photoresists. Low Đ polymers correlate with better pattern resolution as exemplified by lower LER and LWR …”

“…One common drawback that renders ATRP and RAFT undesirable for photoresist materials is the requirement of metal catalysts and the chain transfer agents respectively, which cause undesirable coloration and have to be removed through additional purification steps in order to meet the high purity standards used in the microelectronic industry. It should be noted that variants of ATRP like SET‐LRP and ARGET employ < 50 ppm quantities of Cu catalyst with nearly colorless resins have been shown and in the case of SET‐LRP, monomers used for photoresists were applied.…”

Synthesis of Narrow Molecular Weight Distribution Norbornene-Lactone Functionalized Polymers by Nitroxide-Mediated Polymerization: Candidates for 193-nm Photoresist Materials

“…For example, polymers are often used as photoresists to imprint desired patterns onto a substrate. Two CRP techniques, such as atom transfer radical polymerization (ATRP) [36][37][38][39] and reversible addition fragmentation chain transfer (RAFT) [40][41][42], have been used in the past to synthesize well-defined statistical copolymers with narrow molecular weight distribution for photoresists. Parameters that characterize pattern resolution, such as the line edge roughness (LER) and line width roughness (LWR), are influenced by physical/chemical properties, such as molecular weight, dispersity, composition and microstructure [41,[43][44][45][46].…”

“…Parameters that characterize pattern resolution, such as the line edge roughness (LER) and line width roughness (LWR), are influenced by physical/chemical properties, such as molecular weight, dispersity, composition and microstructure [41,[43][44][45][46]. However, one drawback that makes ATRP and RAFT undesirable for photoresist materials is the requirement of metal catalysts and the chain transfer agents, respectively [42,45], which cause undesirable coloration, pungent odor and have to be removed through additional purification steps in order to meet the high purity standards used in the microelectronic industry. Indeed, the electronic/optical materials generally demand the metallic catalyst concentration to be below 1 ppm to avoid unfavorable photochemical effects [47,48].…”