Extreme ultraviolet holographic microscopy and its application to extreme ultraviolet mask-blank defect characterization

100-nm-resolution at-wavelength holographic microscopy of aerial images pro duced by extreme ultraviolet (EUV) lithographic optics has recently been de monstrated. It provides a simple and compact method allowing image monitori ng without printing in photoresist. Here, the concept of holographic micros copy is extended to the characterizations of defects on EUV multilayer mask blanks. As a proof of principle, defect characterization using the hologra phic microscope is demonstrated with programmed defects in transmission mas ks. Amplitude defects as small as 100 nm have been successfully characteriz ed. Extension of this technique to the more relevant reflection mask config uration is also discussed. (C) 2000 American Vacuum Society. [S0734-211X(00 )02506-3].