Patent ID: 8335038

Claim:
An apparatus for measuring an aerial image, the apparatus comprising: a movable unit adapted to move a reflective extreme ultra-violet (EUV) mask disposed thereon in an x-axis and/or y-axis direction; an X-ray mirror arranged on the movable unit, the X-ray mirror being adapted to selectively reflect a coherent EUV light having a selected wavelength; a zoneplate lens that is located between the movable unit and the X-ray mirror, the zoneplate lens being adapted to focus the coherent EUV light on a portion of the reflective EUV mask; and a detector arranged on the movable unit, the detector being adapted to sense energy of the reflected coherent EUV light when the focused coherent EUV light is reflected by the portion of the reflective EUV mask, wherein numerical apertures of the zoneplate lens and detector are based on parameters of a scanner used to form a pattern through the EUV mask, the parameters of the scanner including a numerical aperture, an off-axis degree, and a reduction magnification.