Patent ID: 7551273

Claim:
A mask defect inspection apparatus, comprising: an illumination optical system which illuminates a plurality of illumination areas including at least a first illumination area and a second illumination area different from each other of a mask on which a pattern is formed; an objective lens facing the mask; a first focusing lens which receives first illumination light from the first illumination area of the mask obtained through the objective lens; a second focusing lens which receives second illumination light from the second illumination area of the mask obtained through the objective lens; a first detection sensor which obtains an image of the pattern in the first illumination area of the mask based on the first illumination light received by the first focusing lens; a second detection sensor which obtains an image of the pattern in the second illumination area of the mask based on the second illumination light received by the second focusing lens; a first moving mechanism which moves the first detection sensor in a direction of an optical axis of the first detection sensor to change a position of focusing between sites of the pattern in the first illumination area in a film-thickness direction of the mask and the image of the pattern obtained by the first detection sensor, such that the image of the pattern obtained by the first detection sensor is changed corresponding to the film-thickness direction of the mask; and a second moving mechanism which moves the second detection sensor in a direction of an optical axis of the second detection sensor to change a position of focusing between sites of the pattern in the second illumination area in the film-thickness direction of the mask and the image of the pattern obtained by the second detection sensor, such that the image of the pattern obtained by the second detection sensor is changed corresponding to the film-thickness direction of the mask.