13 March 2015 Advanced coatings for next generation lithography
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Beyond EUV lithography at 6.X nm wavelength has a potential to extend EUVL beyond the 11 nm node. To implement B-based mirrors and to enable their industrial application in lithography tools, a reflectivity level of > 70% has to be reached in near future. The authors will prove that transition from conventional La/B4C to promising LaN/B4C multilayer coatings leads to enhanced optical properties. Currently a near normal-incidence reflectivity of 58.1% @ 6.65 nm is achieved by LaN/B4C multilayer mirrors. The introduction of ultrathin diffusion barriers into the multilayer design to reach the targeted reflectivity of 70% was also tested. The optimization of multilayer design and deposition process for interface-engineered La/C/B4C multilayer mirrors resulted in peak reflectivity of 56.8% at the wavelength of 6.66 nm. In addition, the thermal stability of several selected multilayers was investigated and will be discussed.
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P. Naujok, P. Naujok, Sergiy Yulin, Sergiy Yulin, N. Kaiser, N. Kaiser, A. Tünnermann, A. Tünnermann, "Advanced coatings for next generation lithography", Proc. SPIE 9422, Extreme Ultraviolet (EUV) Lithography VI, 94221K (13 March 2015); doi: 10.1117/12.2085764; https://doi.org/10.1117/12.2085764

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