EUV dark-field microscopy for defect inspection

An actinic EUV microscope for defect detection on mask blanks for operation in dark field using a table-top discharge-produced plasma source has been developed. Several test structures (pits and bumps) on multilayer mirrors were investigated by our Schwarzschild objective-based EUV microscope at 13.5-nm wavelength and then characterized with an atomic force microscope. Possible defect-detection limits with large field of view and moderate magnification are discussed in terms of required irradiation dose and system performance.