Inspection systems and methods for detecting defects on extreme ultraviolet mask blanks

A system for inspecting surface unevenness defects of less than about 10 nanometers in depth on a surface of an unpatterned object, the system comprising:

• a laser for generating an illuminating light beam;
• a set of optical elements with a partial coherence sigma to between about 0.15 to 0.5 for focusing the illuminating light beam onto the surface of the unpatterned object within a focus range of between about −3 to +3 depth of field (DOF), including a defocused value;
• a stage for moving the unpatterned object with respect to the illuminating light beam to inspect the surface of the unpatterned object;
• a time delay integration (TDI) detector for capturing a reflected light beam reflected from the surface in response to the illuminating beam;
• and
• a computer system comprising at least one memory and at least one processor for causing the set of optical elements to focus the illuminating light beam onto the surface of the unpatterned object at a predetermined defocus range and, based on the reflected light beam at the predetermined defocus range, constructing a resultant image and analyzing the resultant image to identify the surface unevenness defects so as to distinguish between pit defects and bump defects.