Reflective optical element for arrangement near e.g. box in extreme UV lithography device that, has multi-position system for providing wavelength at range, where waves exhibit surface layer with thickness that lies between two thicknesses

摘要

The element (20) has a multi-position system for providing an operating wavelength in an extreme UV (EUV) wavelength range, where electromagnetic waves are reflected at a reflective area (21) at the EUV wavelength range. The reflected electromagnetic waves exhibit a phase and a surface layer with a thickness. The phase is varied based on the thickness of the surface layer such that the phase drops until a thickness is reached. The thickness of the surface layer is designed such that the thickness of the surface layer lies between the thickness and another thickness. An independent claim is also included for an optical system for use in a EUV lithography device.