Patent ID: 8879055
Filing Date: 2014-11-04
Classification: G01N

Abstract:
1. An inspection apparatus that inspects a photomask having a pattern forming surface on which a pattern portion and a light-transmitting portion are formed, and a back surface opposed to the pattern forming surface, the inspection apparatus comprising: an illumination optical system including: a transmitted illumination optical system that projects a transmitted illumination beam toward a back surface of a photomask to be inspected and illuminates a first area of the photomask; and a reflected illumination optical system that projects a reflected illumination beam toward an element forming surface of the photomask and illuminates a second area of the photomask, the second area being smaller than the first area and overlapping the first area in an optical axis direction; a detection system including: a first image pickup element that receives synthetic light of reflected light and transmitted light output from the second area of the photomask and picks up a composite image obtained by optically synthesizing a transmission image and a reflection image of the photomask; and a second image pickup element that receives transmitted light output from a third area of the photomask and picks up a transmission image of the photomask, the third area being a remaining area of the first area excluding the second area; and a signal processing device that is coupled to the detection system, processes an image signal output from the detection system, and outputs data indicating a defect, wherein the transmitted illumination optical system and the reflected illumination optical system are set so as to satisfy b2<b1, when a luminance value of an image of the pattern portion of the composite image is b1 and a luminance value of an image of the light-transmitting portion is b2, and the signal processing device includes: