Patent ID: 7220969

Claim:
A system comprising: a source of extreme ultraviolet (EUV) light to illuminate a multilayered patterning mask blank; a first spherical mirror having a first perimeter and an opening, the first mirror shaped to reflect scattered light to be received from a multilayered patterning mask blank illuminated by the source; a second spherical mirror having a second perimeter, the second mirror shaped to reflect the scattered light received from the first spherical mirror through the opening and to a detector; and a first comparator coupled to the detector to compare a first threshold value to a pixel reflective light intensity value received by the detector for a first pixel of a multilayered patterning mask blank; a second comparator coupled to the detector to compare a second threshold value to a pixel reflective light intensity value received by the detector for a plurality of pixel block reflective light intensity values for a pixel block having a perimeter of adjacent pixels of the multilayered patterning mask blank, wherein the pixel block includes the first pixel.