We constructed an extreme ultraviolet microscope (EUVM) system for actinic mask inspection that consists of
Schwarzschild optics and an X-ray zooming tube. This system was used to inspect finished extreme ultraviolet lithography (EUVL)
masks and Mo/Si coated substrates of ULE glass. And we have fabricated programmed phase defects on the blanks used for
inspection. The EUVM was able to resolve a programmed line-pit defect with a width of 40 nm and a depth of 10 nm, and also with a
width of 70 nm and a depth of 2.0 nm. However, a 75-nm-wide 1.5-nm-deep pit defect was not resolved. Also, the EUVM was able to
resolve a programmed hole-pit defects with widths ranging from 35 nm to 170 nm and depths ranging from 2.5 nm to 2.2 nm.
However, 20-nm-wide 1.5-nm-deep hole-pit defects were not resolved. These results agree with the simulation results perfectly. Thus,
in this study, one critical dimension of a pit defects was experimentaly estimated to be a width of 20 nm and a depth of 2.0 nm.