Development of coherent EUV scatterometry microscope with high-order harmonic for EUV mask inspection

We have developed the standalone, coherent scatterometry microscope (CSM) for the inspection of extreme ultraviolet (EUV) lithography mask. The low divergence, coherent high-order harmonic (HH) was generated as coherent light source for CSM at a wavelength of 13.5 nm using a commercial laser system. The HH enable us to obtain the high contrast diffraction image from the mask. The diffraction light from the 2-nm wide line-defect and tens-nm size point-defects in the mask has been observed successfully with the system.