Apparatus and method of image enhancement through spatial filtering
AssigneeASML Netherlands B.V.
InventorBruce W. Smith
Life of this patent
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Abstract
An image enhancement apparatus and method are disclosed. The apparatus consists of a spatial frequency filter where zero order mask diffraction information is reduced in an alternative pupil plane of the objective lens, specifically just beyond the mask plane. By introducing an angular specific transmission filter into this Fraunhofer diffraction field of the mask, user accessibility is introduced, allowing for a practical approach to frequency filtering. This frequency filtering is accomplished using a specifically designed interference filter coated over a transparent substrate. Alternatively, filtering can also be accomplished in a complimentary region near the wafer image plane or in both near-mask and near-wafer planes.
Claims14
A filter comprising a substrate and one or more thin films coated on the substrate,
- wherein the substrate and the films are highly transparent to a selected wavelength of radiation and are relatively different in their respective indexes of refraction for angularly filtering incident radiation.
Dependencies are inferred from the claim text.