18 October 2004 Design and development of an optical system for EUV-microscopy
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In the paper we describe the development of a reflective optical system for EUV-microscopy containing an ellipsoidal formed collector optics and a Schwarzschild objective (magnification M=21, numerical aperture NA=0.2) for EUV radiation of a wavelength λ=13.5nm. In order to collect the maximum intensity of an EUV gas discharge plasma source, the grazing incidence collector has been inside-coated with molybdenum by Pulsed Laser Deposition (PLD). This method enables the deposition of uniform and highly reflective molybdenum layers, which have been protected against oxydation by using thin carbon top layers. The two mirrors of the Schwarzschild objective consist of highly reflective Mo/Si- multilayers produced by Magnetron Sputter Deposition (MSD). In order to obtain the best optical performance, laterally graded multilayers with rotational symmetry have been deposited by using a new mask-deposition technique. Thus the multilayer thickness corresponds at each point of the curved mirrors to wavelength and incidence angle of the EUV beam. Ray tracing simulations were performed for the two optical elements, collector optics and Schwarzschild objective. The results of these calculations are shown and compared with the results obtained by the EUV-microscope.
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Thomas Foltyn, Thomas Foltyn, Klaus Bergmann, Klaus Bergmann, Stefan Braun, Stefan Braun, Peter Gawlitza, Peter Gawlitza, Andreas Leson, Andreas Leson, Willy Neff, Willy Neff, Konstantin Walter, Konstantin Walter, "Design and development of an optical system for EUV-microscopy", Proc. SPIE 5533, Advances in Mirror Technology for X-Ray, EUV Lithography, Laser, and Other Applications II, (18 October 2004); doi: 10.1117/12.559675; https://doi.org/10.1117/12.559675


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