24 February 2003 Enhancement of multilayer-coated normal incidence gratings in the extreme ultraviolet using a CNx smoothing layer
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Abstract
We describe a novel process to improve the extreme ultraviolet (EUV) reflection efficiency of multilayer-coated replica gratings through an intermediate CNX overcoat. Au-coated and uncoated (SiO2 surface) Hitachi replica gratings (20 x 20 mm, 4800 g/mm, 13° blaze angle), designed to provide peak efficiencies at 304 Å in 3rd order, were measured using an AFM prior to and after the CN$X coating. The CNX coating produced substantially smoother grating facets without significantly degrading the grating groove profile. The gratings were then overcoated with a 10 layer Mo/Si stack optimized for near normal reflectivity at 304 Å. Reflectivity measurements in 3rd order demonstrated an enhancement in absolute grating efficiency by a factor of 4 over the Mo/Si + Au-coated grating. The results of this simple experiment suggest that, with further improvements, the CNX overcoating process may provide a useful and relatively inexpensive alternative to the use of ion-etched blazed gratings in the EUV for some applications.
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Robert A. Stern, Robert A. Stern, Lawrence Shing, Lawrence Shing, Yip-Wah Chung, Yip-Wah Chung, Murat U. Guruz, Murat U. Guruz, } "Enhancement of multilayer-coated normal incidence gratings in the extreme ultraviolet using a CNx smoothing layer", Proc. SPIE 4854, Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation, (24 February 2003); doi: 10.1117/12.459817; https://doi.org/10.1117/12.459817
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