Dual-functional multilayer for high-reflectivity at 19.5 nm and low-reflectivity at 30.4 nm

A dual-functional extreme ultraviolet(EUV) multilayer (ML) mirror was designed for high-reflectivity at 19.5 nm ( Fe Ⅻ line ) and low-reflectivity at 30.4 nm ( He Ⅱ line ). The design based on genetic algorithm (GA) utilized a stack composed of two periodic multilayers: a bottom multilayer for high reflectivity at 19.5 nm, and a top multilayer for low-reflectivity at 30.4 nm. The multilayer mirror was prepared by direct current magnetron sputtering, and characterized by grazing-incident X-ray diffraction(XRD) and synchrotron radiation(SR). The experiment results show that the dual-functional multilayer achieves the reflectivity of 33.3% at 19.5 nm and 9.6×10-4 at 30.4 nm at incident angle of 13°.