11 April 2006 Reactivity of model compounds of ArF immersion, ArF, and KrF resists with diphenylsulfinyl radical cation, a cage-escape product of photochemistry of triphenylsulfonium salts
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Abstract
Reactivity of diphenylsulfinyl radical cation (Ph2S.+) with model compounds of "dry/wet" ArF resists and KrF resists was investigated by pulse radiolysis technique, in order to reveal the reaction between Ph2S.+ and a polymer. Ph2S.+ is an intermediate of photolysis of triphenylsulfonium salts. Some Ph2S.+ react with other intermediate of phenyl radical, leading to the formation of (phenylthio)biphenyl products and proton (H+). The reaction, referred to as rearrangement reaction, is mainly responsible for acid generation. However, some Ph2S.+ react with a polymer. Acid-generation efficiency might be enhanced if H+ is also formed by this reaction. Among 25 model compounds employed, Ph2S.+ was scavenged by phenolic compounds which have lower electrochemical half wave reduction potential (E1/2) than that of Ph2S. However, resulting radical cations of the phenolic compounds were not observed. Ph2S.+ was not scavenged by the other compounds with higher E1/2. Decay rate constant of Ph2S.+ scavenged by additives clearly depends on the change of E1/2 between Ph2S and the additives including pyrene from which charge transfer was observed to Ph2S.+. The reaction is therefore charge transfer between the model compounds and Ph2S.+. The resulting radical cations of phenolic compounds are known to decompose to phenoxy radical and proton (H+), suggesting that the compounds contribute to the enhancement of acid-generation efficiency in a chemically amplified resist. From the viewpoint of reaction of Ph2S. + with resists, conventional polymer of KrF resist is therefore appropriate for H+ source. Phenolic compounds are generally not appropriate for the component of "dry/wet" ArF resists because of their strong absorption at 193 nm. However, the electron proved to be transferred from fluorinated methylphenols to Ph2S.+. Fluorinated methylphenols may have a potential for candidate of resist components improving acid generation in "dry/wet" ArF lithography.
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Yoshinori Matsui, Yoshinori Matsui, Hidekazu Sugawara, Hidekazu Sugawara, Shou Tsuji, Shou Tsuji, Toshiro Itani, Toshiro Itani, Shu Seki, Shu Seki, Takahiro Kozawa, Takahiro Kozawa, Seiichi Tagawa, Seiichi Tagawa, } "Reactivity of model compounds of ArF immersion, ArF, and KrF resists with diphenylsulfinyl radical cation, a cage-escape product of photochemistry of triphenylsulfonium salts", Proc. SPIE 6153, Advances in Resist Technology and Processing XXIII, 61530I (11 April 2006); doi: 10.1117/12.655087; https://doi.org/10.1117/12.655087
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