Abstract
This paper describes an overview of the manufacture and measurement of aspherical mirrors for X-ray optics. In X-ray lithography and astronomical observation, to which X-ray optics are typically applied, especially in EUV lithography that uses extra ultraviolet light, it is necessary to achieve a degree accuracy of 0.25 nm RMS, which is higher than that in the past. The manufacture of this kind of mirror requires a high level of technology for three domains: figuring (low spatial frequency), smoothing ripples (mid-spatial frequency) and surface roughness (high spatial frequency). Polishing is the most reliable technique for these three domains. Therefore, stabilization of the polishing process is the most important factor in improving the accuracy of the mirrors. The measurement accuracy for roughness and ripple is now approaching the target value for the manufacture of EUV optics. A new interferometer that utilizes point diffraction has been developed, providing an accuracy of 0.5 nm RMS. Increasing the aspherical surface volume remains a goal for the future.
