Patent ID: 6489627
Filing Date: 2002-12-03
Classification: G01N,G03F

Abstract:
A method for inspecting a reticle comprising:providing a reticle comprising a transparent substrate having formed thereupon a patterned non-transparent layer which defines an alignment mark; impinging at a non-orthogonal angle through the alignment mark within the reticle an inspection light beam which is both: (a) refracted and transmitted directly through the reticle; and (b) refracted, reflected and then transmitted through the reticle, to thus provide a multiplicity of refracted transmitted inspection light beams; passing the multiplicity of refracted transmitted inspection light beams through a pair of transparent wedges whose inclined surfaces are counter-opposed and separated by a gap to form a series of additionally refracted transmitted inspection light beams; and varying a distance of the gap to optimize an optical characteristic of the additionally refracted transmitted inspection light beams.