Sub-nm figure error correction of an extreme ultraviolet multilayer mirror by its surface milling

Detailed calculation of reflection phase shows that surface milling of extreme ultraviolet multilayer mirrors after fabrication is useful for accurate correction of figure errors with a correction sensitivity of 0.1 nm. The optical principle of the correction is described and example calculations of phase shift and reflectance variation by the milling are shown with a Mo/Si multilayer structure at a wavelength of 12.8 nm.