Conventional and modified Schwarzschild objective for EUV lithography: design relations
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The design criteria of a Schwarzschild-type optical system are reviewed in relation to its use as an imaging system in an extreme ultraviolet lithography setup. Both the conventional and the modified reductor imaging configurations are considered, and the respective performances, as far as the geometrical resolution in the image plane is concerned, are compared. In this connection, a formal relation defining the modified configuration is elaborated, refining a rather naïve definition presented in an earlier work. The dependence of the geometrical resolution on the image-space numerical aperture for a given magnification is investigated in detail for both configurations. So, the advantages of the modified configuration with respect to the conventional one are clearly evidenced. The results of a semi-analytical procedure are compared with those obtained from a numerical simulation performed by an optical design program. The Schwarzschild objective based system under implementation at the ENEA Frascati Center within the context of the Italian FIRB project for EUV lithography has been used as a model. Best-fit functions accounting for the behaviour of the system parameters vs. the numerical aperture are reported; they can be a useful guide for the design of Schwarzschild objective type optical systems.
KeywordsNumerical Aperture Object Plane Object Position Design Relation Projection Optic
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- 3.D. Attwood, Soft X-Ray and Extreme Ultraviolet Radiation: Principles and Applications (Cambridge University Press, Cambridge, 1999)Google Scholar
- 4.G. Baldacchini, A. Baldesi, S. Bollanti, F. Bonfigli, G. Clementi, A. Conti, T. Dikonimos, P. Di Lazzaro, F. Flora, M. Francucci, A. Gerardino, R. Giorgi, A. Krasilnikova, T. Letardi, N. Lisi, T. Marolo, S. Martellucci, L. Mezi, R.M. Montereali, D. Murra, E. Nichelatti, P. Nicolosi, L. Palladino, A. Patelli, M.G. Pelizzo, A. Piegari, S. Prezioso, A. Reale, V. Rigato, A. Ritucci, A. Santoni, F. Sarto, F. Scaramuzzi, E. Tefouet Kana, G. Tomassetti, A. Torre, C.E. Zheng, in XXVII ECLIM Conf., Rome, Italy, 6–10 September 2004Google Scholar
- 5.G. Baldacchini, A. Baldesi, C. Bellocci, S. Bollanti, F. Bonfigli, G. Clementi, A. Conti, T. Dikonimos, P. Di Lazzaro, F. Flora, M. Francucci, P. Gaudio, A. Gerardino, R. Giorgi, A. Krasilnikova, T. Letardi, N. Lisi, T. Marolo, S. Martellucci, L. Mezi, R.M. Montereali, D. Murra, E. Nichelatti, P. Nicolosi, L. Palladino, A. Patelli, M.G. Pelizzo, A. Piegari, A. Reale, M. Richetta, V. Rigato, A. Ritucci, A. Ridzy, A. Santoni, F. Sarto, F. Scaramuzzi, E. Tefouet Kana, G. Tomassetti, A. Torre, C.E. Zheng, in ICXOM-XVIII Conf., Frascati (Rome), Italy, 25–30 September 2005Google Scholar
- 8.S. Bollanti, P. Di Lazzaro, F. Flora, L. Mezi, D. Murra, A. Torre, in Optical Design and Engineering II (SPIE 5962), ed. by L. Mazuray, R. Wartmann (SPIE, Bellingham, 2005), 5962Y-1. Here the simulation has been performed by entering into the ZEMAX code the object-space numerical aperture, determined as the image-space numerical aperture divided by the paraxial demagnification factor of the ordinary SO setup, i.e. NA/M. As expected, the difference from the results obtained by entering the working F/# becomes perceivable in the MSO configuration. Evidently, choosing the object-space numerical aperture or the working F/# as input parameter to the ZEMAX code corresponds to the ‘philosophy’ of configuring the MSO setup starting respectively from the object-space or image-space configuration of the relevantGoogle Scholar
- 9.K. Schwarzschild, Abh. Wiss. Goett. Math. Phys. K1 NF 4, 1 (1905)Google Scholar
- 10.Information on and a demonstration version of the ZEMAX package are in www.optima-research.com. A comparative analysis of performances and costs of various optical design softwares can be found in ‘Design software: which package do you need?’, Opt. Laser Eur., July–August 2003, 19–21 [http://optics.org]Google Scholar