12 May 2004 The modeling of immersion liquid by using quantum chemical calculation
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Abstract
For realizing next generation 193nm immersion lithography, developing suitable high refractive index liquid is an very important issue. To overcome the trade off relationship between high refractive index (optimally more than 1.6 ) and low absorbance (similar degree with H2O 0.0036cm-1), the molecular modeling based on quantum chemical ab-initio calculation was performed. We have successfully developed the predictive method of frequency-dependent refractive index for liquid and its absorbance. Then, we tried to estimate these properties to search for optimal candidates. In this paper, we report on the estimated results of the refractive index n and the absorbance at 193nm for some candidate compounds. We believe we could demonstrate the usefulness of the predictive method by using the quantum chemical calculation for developing new liquids, even if there were some degree of errors in the absolute values. We have found the -SO2- (like sulfone, sulfonate, sulfate) containing five- and six-membered ring compounds such as sulfolane and sultone etc. would achieve both high refractive index around 1.6 and relatively low absorbance. XeF4O and Bi(CF3)3 ,unfortunately, had absorption at 193nm due to the weak binding outer valence electrons. In the case of alkyl Si and Ge, Si(CH2CH3)4 might have a good balance of refractive index 1.59 and relatively low absorbance. Si(CH3)3CH2CH2OH and Ge(CH2CH3)4 were estimated to have refractive index of over 1.6, but have been estimated these might have sightly stronger absorption.
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Jun Irisawa, Takashi Okazoe, Takeshi Eriguchi, Osamu Yokokoji, "The modeling of immersion liquid by using quantum chemical calculation", Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2004); doi: 10.1117/12.598703; https://doi.org/10.1117/12.598703
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