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26 March 2008 Highly hydrophobic materials for ArF immersion lithography
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In immersion lithography, the impact of water on resist performance and the possibility of damage to the lens by the components eluted from the resist material are seriously concern. And much work has shown that controlling the water-resist interface is critical to enabling high scan rates. Many topcoat materials have been developed to control the aforementioned interfacial properties. Developable topcoats have been particularly investigated as suitable candidates for its applicability to the resist developing process. Achieving the balance between the low surface energy required for higher receding contact angle and the base solubility for topcoat removal is challenging. We have already reported FUGU polymer which have partially fluorinated monocyclic structure and hexafluoroalcohol(HFA) group and showed that its developer solubility was excellent but hydrophobicity was insufficient for high scan rate. We have also reported that co-polymers of FUGU and highly fluorinated monomers which have perfluorinated cyclic structure had sufficient hydrophobicity but lower developer solubility. We have found that it was difficult to use these copolymers in themselves as topcoat. But by blending of moderate amount of these copolymers into FUGU polymer, we have finally obtained highly hydrophobic developer-soluble topcoat. Hydrophobicity can be controlled by blending ratio. Furthermore we have newly successfully synthesized a series of fluoropolymers, FIT polymer partially fluorinated monocyclic structure and having carboxylic acid group as developer-soluble unit. When FIT polymer as well as FUGU polymer, was blended to highly hydrophobic copolymer, the blended polymer also showed higher hydrophobicity keeping sufficient developer solubility.
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Yoko Takebe, Naoko Shirota, Takashi Sasaki, Koichi Murata, and Osamu Yokokoji "Highly hydrophobic materials for ArF immersion lithography", Proc. SPIE 6923, Advances in Resist Materials and Processing Technology XXV, 69231U (26 March 2008);

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