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2 April 2007 Development of non-topcoat resist polymers for 193-nm immersion lithography
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Recently it is known well that blending hydrophobic additives into conventional resist polymer drastically improve its film surface hydrophobicity. So we thought that this approach was one of candidates and most promising to achieve a non-topcoat resist process for immersion lithography. And it would be able to maintain original resist performance because only a small amount of additives were added into conventional resist. Then we have investigated hydrophobic polymers for use as additives of non-topcoat resists. We have newly successfully synthesized various new highly fluorinated monomers by our peculiar fluorination process. We found that some specific methacrylate ,which have perfluorinated cyclic structure, showed excellent hydrophobicity. The other hydrophobic candidates is our fluoropolymer, FUGU, which had already developed, having partially fluorinated monocyclic structure. However its hydrophobicity is insufficient due to presence of acidic hydroxyl group which act as dissolution unit into the developer. To improve the its hydrophobicity, we protected all or a part of its hydroxyl group. The protected FUGU polymer provide good hydrophobicity whose sliding angle (S.A.) and receding angle (R.A.) were 7 degree and 90 degree respectively , compared to original polymer, FUGU. In this paper, we describe a characteristics and evaluation of these our hydrophobic polymers to apply to additives for non-topcoat resists. We have optimized these polymers to apply to additive for conventional resist. As a result, various kinds of additives were obtained. For example, some of them dissolve in developer due to the presence of alkali soluble group in the polymer, the others are soluble in developer after deprotection reaction by post exposure bake. We call the former one is 'top-coat type', the latter is 'resist type'. Two type additives were investigated to give the hydrophobicity and to depress the leaching amount to conventional resist.
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Naoko Shirota, Yoko Takebe, Shu-Zhong Wang, Takashi Sasaki, and Osamu Yokokoji "Development of non-topcoat resist polymers for 193-nm immersion lithography", Proc. SPIE 6519, Advances in Resist Materials and Processing Technology XXIV, 651905 (2 April 2007);

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