Concept of ultra-fast at-wavelength inspection of defects on multilayer mask blanks using a laser-produced plasma source

New configuration is presented for ultra-fast at-wavelength inspection of defects on multilayer mask blanks. Key idea are detecting defects in a high NA dark-field observation by using a Schwarzschild objective, sub-micron resolution two-dimensional imaging of mask surface on a detector, and large etendue illumination by using a laser-plasma source. Expected time for inspecting a whole mask is shorter than 2 hours.