Development fo High Reflectivity Multilayr Mirrors in the Extreme Ultraviolet Region(60nm-20nm)

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High reflectivity mirrors in the extreme ultraviolet (EUV) region (60nm-20nm) are strongly required from the EUV microscopy, the plasma diagnostics and astronomical observation by using the EUV light, and the EUV laser exploitation. In this study, we developed multilayr mirrors having high reflectivity especially at resonance lines of He I (58.4nm) and He II (30.4nm), and the 3p edge of Ni (20nm). We fabricated the multilayrs designed theoretically using magnetron and ion-beam sputtering-instruments. Their reflectivities were checked with reflectometers attached to a grazing incidence monochromator with a plasma induced light source and a Seya-Namioka monochromator with a He discharge lamp. The multilayrs with the highest reflectivity are a Si/W bilayr (21.6% at 58.4nm), a Sc/Mg multilayr (27% at 30.4nm) and a Mo/Si multilayr (18% at 20nm). As an important application of the multilayrs, we have tried to enhance the diffraction efficiency of a grating around 30nm under normal incidence condition. We coated the surface of the grating with a Mo/Si multilayr and obtained very high diffraction efficiency of 5%. This is very distinguishable result of this project, which enable us to get 30nm light without use of a grazing incidence monochromator. We also tried to fabricate multilayrs having crystalline structure using an MBE instrument, checking the crystallinity with an RHEED monitor, but this trial has not been succeeded yet.At present, the reflectivity of each fabricated multilayr is smaller than the value calculated theoretically. It may be due to the roughness of interface in multilayrs. We will try to reduce the roughness by controlling precisely the substrate temperature with an infrared heater. Furthermore, we will develop the EUV microscopes using the high reflectivity multilayr mirrors.