Charged-particle beam optical apparatus for imaging a mask on a specimen

摘要

An improved charged-particle beam optical apparatus for imaging a first mask including a plurality of apertures on a specimen to be irradiated. The mask is uniformly illuminated by a beam through a plurality of condenser lenses and the apparatus includes means for adjusting the position of the mask relative to the specimen. A selected area of the specimen has an adjustment marking disposed thereon which is illuminated by a ray of charged particles from the beam passing through a test opening provided in the mask. The apparatus further includes means for detecting radiation emanating from the specimen. The improvement of the invention comprises the provision of a second mask, having at least one aperture which is alignable with the test opening in the first mask, mounted in the apparatus and movable into positions above and below the first mask for aligning the test opening and aperture in the first and second masks and covering the plurality of apertures in the first mask so as to permit charged particles from the beam to pass only through the test opening in the first mask and the aperture in the second mask.