Fabrication and characterization of EUV multilayer gratings
Résumé
By matching multilayer Bragg interference and grating diffraction conditions, EUV multilayer gratings provide high spectral resolution (λ/∆λ > 1000) with efficiencies similar to the reflectance of the multilayer coating. Such components are of particular interest for EUV spectro-imaging application. In this work, we optimized and studied periodic multilayer on gratings with trapezoidal shape in order to reach a maximum 1st order efficiency at wavelengths ranging from 25 nm to 29 nm, a region of particular interest for solar corona spectro-imaging [1]. We have recently reported on Al/Mo/SiC multilayer diffraction gratings with broadband efficiency in the extreme ultraviolet [2]. We report here on the fabrication and characterization of the groove profile evolution after deposition using TEM and AFM analyses. Different kind of multilayers have been deposited by magnetron sputtering [3] and ion beam sputtering [4] on grating substrates with high groove density (> 3600l/mm). We used both fused silica grating substrates provided by Zeiss (holographic process) and silicon grating substrates processed in our lab via e-beam lithography. The results obtained with different material combination for the multilayer, different grating substrates and different deposition technics will be discussed and compared.