STRUCTURE AND PERFORMANCE OF SI MO MULTILAYER MIRRORS FOR THE EXTREME-ULTRAVIOLET/

We report the results of structural, chemical, and extreme ultraviolet (EUV) characterization of Si/Mo multilayers grown by sputtering and b y UHV evaporation. This study includes mirrors designed for normal inc idence with peak reflectivities R(peak) between 22 and 24 nm, and 45-d egrees mirrors having R(peak) between 16 and 19 nm. The deposition con ditions were varied to produce multilayers with a wide range of interf ace morphologies. A variety of techniques were used to determine the s tructure and composition of the multilayers, including x-ray diffracti on, transmission electron microscopy, Rutherford backscattering spectr oscopy, and Auger depth profiling. All of the mirrors have amorphous S i layers and polycrystalline Mo layers with thin amorphous alloy inter layers. We obtain good fits to the low-angle x-ray diffraction data on ly when these interlayers are taken into account. The best sputter-dep osited mirrors were made at the lowest Ar pressure studied, 3 mTorr. T he best evaporated mirrors were produced at a substrate temperature of 200-degrees-C. The EUV reflectivity as a function of wavelength was m easured using synchrotron radiation. Both the multilayer structure and surface contamination significantly affect the EUV reflectivity, and must be considered to obtain good fits to the reflectivity curves. The best 45-degrees mirror had a peak reflectivity of 53% at 18.6 nm for 100% S-polarized light, and the best normal-incidence mirror had a pea k reflectivity of 33% at 23.6 nm.