Patent ID: 7005235

Claim:
A method combining interferometric and optical photolithography for producing, in a substrate, an arbitrary pattern of sub-micron holes from an array of such holes comprising: providing a substrate covered with a photosensitive material; exposing said substrate with a first radiative exposure using a first standing wave interference pattern produced by a superposition of coherent beams of electromagnetic radiation; exposing said substrate, subsequent to said first exposure, with at least a second radiative exposure using a second standing wave interference pattern produced by a superposition of coherent beams of electromagnetic radiation and creating, thereby, an interferometric array of exposed and unexposed regions in said photosensitive material, from which unexposed regions will be formed the selected pattern of holes; placing a non-critical mask above said substrate and exposing said mask and substrate to a uniform flux of electromagnetic radiation such that said radiation passes through the transparent portion of said mask and exposes a corresponding portion of the photosensitive material on the substrate; developing said photosensitive material, removing, thereby all remaining unexposed areas of said material which now comprise the areas beneath the opaque portion of the mask that were unexposed before placement of the mask; wherein the interference producing superposition is formed by sending a single laser beam through a beam expander, reflecting said expanded beam from a first reflecting surface such that a lower portion of said reflected beam strikes the substrate while an upper portion of said beam strikes a second reflecting surface that is perpendicular to said substrate and which reflects said upper portion also onto the substrate, the lower and upper portions now making equal angles with the normal to the substrate and being symmetrically disposed about said normal.