EUV multilayer mirrors and their applications

In Japan, multilayer mirror development has been underway since the early 1980s at institutes such as Tohoku University, NTT, Canon, Nikon. NTT applied multilayer mirrors for what is now known as EUVL (Extreme Ultraviolet Lithography, formerly called Soft-Xray Projection Lithography) and developed an early- stage optical system for EUVL, initially using W/C multilayer mirrors. Later on, Mo/Si multilayer mirrors with high reflectivity near a wavelength of 13 nm were employed as the EUVL multilayer mirrors. Since then, Mo/Si multilayer mirrors have remained effective in EUV applications, leading to various applications. In this talk, the development of Mo/Si multilayer mirrors and their applications mainly in Japan will be introduced.