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

EUV显微镜、利用EUV进行等离子体诊断和天文观测以及EUV激光的开发都迫切需要在EUV(60 nm-20 nm)范围内获得高反射率的反射镜。在本研究中，我们研制了具有高反射率的多层反射镜，特别是在He I(58.4 nm)和He II(30.4 nm)的共振线，以及Ni的3p边(20 Nm)。我们用磁控管和离子束溅射仪制作了理论设计的多层膜。它们的反射率用安装在带有等离子体诱导光源的掠入射单色器和带有氦放电灯的Seya-纳米冈单色器上的反射计来检查。反射率最高的薄膜是Si/W双层(58.4 nm处21.6%)、Sc/Mg多层膜(30.4 nm处27%)和Mo/Si多层膜(20 nm处18%)。作为多层膜的一个重要应用，我们尝试了在垂直入射条件下提高约30 nm的光栅的衍射效率。我们在光栅表面涂覆了Mo/Si多层膜，获得了5%的很高的衍射效率。这是这个项目非常明显的结果，它使我们能够在不使用掠入射单色仪的情况下获得30 nm的光。我们还尝试用分子束外延仪制备具有晶体结构的多层膜，用RHEED检测结晶度，但实验还没有成功，目前制备的多层膜的反射率都小于理论计算值。这可能是由于多层膜中界面的粗糙所致。我们将尝试通过用红外线加热器精确控制基片温度来降低粗糙度。此外，我们将使用高反射率的多层反射镜来开发极紫外光显微镜。

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.