Photoelectron image projection apparatus

Claim 1

A photoelectron beam image projection apparatus for detecting defects in a pattern, to be projected as a photoelectron beam image onto a wafer, relative to a desired pattern, the pattern to be projected being defined by a mask having a photoelectric layer thereon and the photoelectron beam image of the pattern being formed by selective irradiation of the photoelectric layer through the mask pattern and the corresponding release of photoelectrons from the selectively irradiated photoelectric layer, comprising: a projection chamber; means for holding the mask within said projection chamber; means for emitting a light beam; means for directing said light beam selectively onto each of plural, predetermined regions of the mask pattern, thereby to selectively irradiate respectively corresponding, plural regions of said photoelectric layer as defined by said mask pattern; means for forming the photoelectrons released from each said selectively irradiated region of the photoelectric layer into a corresponding photoelectron beam and for projecting each said corresponding photoelectron beam so as to form a respectively corresponding photoelectron beam pattern region image on a predetermined image plane within said projection chamber; image detector means positionable at said image plane for being irradiated by and detecting each said projected photoelectron beam pattern region image and producing a corresponding, detected pattern region image output signal; movable stage means, disposed within said projection chamber, for holding and selectively positioning said wafer and said detector means within said projection chamber, said movable stage means being selectively movable to a first position at which said detector means is positioned at said image plane for being irradiated by each said projected photoelectron beam pattern region image and to a second position at which said wafer is positioned at said image plane for being irradiated by each said projected photoelectron beam pattern region image; and defect detector means for providing reference pattern region image signals for respectively corresponding, plural and predetermined regions of said desired pattern and for comparing each said detected pattern image region output signal of said image detector means with the respective reference pattern region image signal and producing a defect indication output signal when said compared signals differ.