| 摘要 |
According to the present invention, inspection light is irradiated onto a photomask blank to be inspected, and a reflection light on a region of the photomask blank to be inspected, onto which the inspection light is irradiated, is collected as an extended image of the region through an object lens of an inspection optical system. An intensity change part of a light intensity distribution profile of the extended image is specified. A difference of light intensity in the intensity change part is obtained, and a width of the intensity change part is obtained as an apparent width of defection. A width of defection is calculated through a particular conversion formula which shows correlation of a difference of light intensity, an apparent width of defection, and a width of actual defection, so a width of defection is estimated and a defection size of a photomask blank is evaluated. By using such an optical defection size evaluating method, a defection size of a photomask blank may be evaluated at a high degree of precision even in a size region having a resolution which is equivalent to or less than a nominal resolution of an inspection optical system. |
