Development of soft X-ray multilayer mirrors for a wavelength of 3nm

Fabrication process of soft X-ray multilayer mirrors composed of Sc/Cr having shown high reflectances above 10% including the highest 14.8% for a wavelength of 3nm is described. The multilayers mere prepared by ion beam sputtering of an electron cyclotron resonance type enabling sputter deposition at the highest vacuum of 0.03mTorr. The multilayers were prepared at a stable deposition rate within 4 hours to suppress period instability and also at various substrate temperatures to find the best condition to suppress the interface roughness.