23 January 2006 Novel method for fabrication of high-efficiency optics for short wavelength radiation
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Extreme ultraviolet lithography (EUVL) is the most likely next generation lithography technique which uses radiation near 13.4 nm wavelength. At this short wavelength, most materials readily absorb the radiation, making refractive lens optical systems unusable. We demonstrate a novel method for fabrication of highly efficient optics for extreme ultraviolet (EUV) radiation using focused ion beam (FIB). These optics are based on Fresnel zone plates, similar to those used for x-ray microscopy, but with a geometry to improve the efficiency for EUV radiation. A typical zone plate has concentric rings with a radially decreasing feature size such that the path of light through every second zone to the focus differs by one optical wavelength following the Bragg's Law. An optic with a net efficiency of 21% can be achieved for 13.4 nm radiation using the standard zone plate design with 86 nm thick zones made from Mo and mounted on a 50 nm silicon nitride membrane. Further improvement in the efficiency can be achieved by fabricating blazed zone plates, which can have a net efficiency of 40% when fabricated on a 50 nm silicon nitride membrane. These lenses are cheap to manufacture and easy to align for imaging since it is a single optic. The preliminary data will be presented on the fabrication of both standard and blazed zone plates optimized for EUV radiation.
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Rashi Garg, Rashi Garg, James Evertsen, James Evertsen, Gregory Denbeaux, Gregory Denbeaux, } "Novel method for fabrication of high-efficiency optics for short wavelength radiation", Proc. SPIE 6110, Micromachining Technology for Micro-Optics and Nano-Optics IV, 61100S (23 January 2006); doi: 10.1117/12.646492; https://doi.org/10.1117/12.646492


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