1 April 2008 EUV optics contamination studies in presence of selected hydrocarbons
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Abstract
One of the remaining challenges for the commercialization of EUV lithography is the lifetime of the Mo/Si multilayer optics and masks. The lifetime is dominated by carbon contamination on the surfaces of the optics, which is caused by residual hydrocarbons in the vacuum chamber when optics are exposed to EUV radiation. One of the possible sources of the hydrocarbons in the chamber is resist outgassing. To be able to understand which type of hydrocarbons are harmful to EUV mirror reflectivity, three hydrocarbon species - benzene, tert-butanol and diphenyl sulfide - which are thought to be representative of commonly outgassed species from EUV photoresist were selected. The goal of this work was to measure the contamination rate from these three species and to be able to draw conclusions about other species. The results of the experiments showed that after 8 hours of exposure there was not enough contamination to be significantly measurable. In addition to these hydrocarbon species, we also used vacuum grease and carbon tape as an outgassing source for hydrocarbons. Comparatively, high contamination rates were achieved with vacuum grease and carbon tape.
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R. Garg, A. Wüest, E. Gullikson, S. Bajt, G. Denbeaux, "EUV optics contamination studies in presence of selected hydrocarbons", Proc. SPIE 6921, Emerging Lithographic Technologies XII, 692136 (1 April 2008); doi: 10.1117/12.772770; https://doi.org/10.1117/12.772770
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