Patent ID: 6335151
Filing Date: 2002-01-01
Classification: G02B,G03F

Abstract:
A lithographic process for fabricating a microscopic, three dimensional surface, comprised of the steps of:a) creating a mask, consisting partly or wholly of subresolution patterns, by determining pixels p, wherein p is the square formed by the minimum addressable pattern size of the mask-creating process, determining superpixels P, wherein P is the square formed by the maximum unresolved pitch of the lithographic process, determining the local pattern density d defined by d=np/P where n is an integer greater than 1, and determining the density of the subresolution patterns defined by d2(x,y)=1âˆ’exp[âˆ’&agr;S(x,y)] where &agr; is the absorption coefficient of a resist material and S(x,y) is the desired surface; b) imaging the mask pattern on an absorbing photoresist film of a predetermined absorption and a predetermined thickness t0, the thickness of the photoresist film is defined by t0, E(x,y)<Et t(x,y)=t0âˆ’&agr;âˆ’1 ln[E(x,y)/Et], Et(x,y)<Et exp(&agr;t0) 0, Et exp(&agr;t0)<E(x,y) where E(x,y) is the image energy and Et is the threshold energy; and c) transferring the three-dimensional surface to a substrate wherein the surface transferred is related to the substrate surface by a relative etch selectivity, K, and wherein the initial mask density is defined by d2(x,y)=1âˆ’exp[âˆ’&agr;S(x,y)/K].