Development of a surface gradient integrated profiler for the next generation high accuracy mirror

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In order to develop X-ray free electron laser sources, the ultraprecision asymmetric mirrors which realize nano-focusing and high coherence are indispensable. In industry, the high accurate asymmetric mirrors are required for extreme ultraviolet lithography which is a promising fabrication technology for semiconductor devices.A surface gradient integrated profiler can be developed for the next generation high accuracy asymmetric mirrors. The new profiler is based on the straightness of laser light without a reference surface. The performances of the profiler are as follows. The accuracy of measurement of the mirror profile is 1 nmPV. The resolution of measurement of the rotation angle is 0.17 μrad. And the time of measurement is 5 min/sample. A spherical mirror with a radius of 400 mm is measured by the profiler. The repeatability of two-dimensional profile measurements is less than 1 nm. The profile of the spherical mirror with R = 400 mm to be measured by using the profiler is compared with that measured by using the Fizeau interferometer and coordinate measuring machine. The profile measured by using the profiler coincides with that measured by using other profilers, within approximately 10 nm. These differences of profiles are based on systematic errors, respectively.