Development of EUV wavefront metrology technology in ASET

Summary form only given, as follows. We examined several wavefront metrology techniques suitable for EUV optics. Problems are lack of high-coherence light source and limitation of applicable optical elements in the EUV wavelength region. To overcome these problems, we adopted point diffraction interferometry (PDI) and shearing interferometry as candidates of metrology method. To verify the idea, we have designed a simple EUV experimental interferometer, which is now under fabrication. The system can be used as both a PDI and a shearing interferometer, with which we will extract issues on wavefront metrology of relatively high-NA EUV optics and will compare the metrology methods. The detailed system design and progress will be presented at the conference.