Lithographic patterning of curved substrates

Abstract

For producing an exposure pattern on a curved, in particular concave substrate field of a substrate which comprises a layer of resist material sensitive to exposure to an energetic radiation, in a pattern transfer system a wide, substantially parallel beam of said energetic radiation is produced, and by means of said beam a planar mask having a structure pattern, namely, a set of transparent windows to form a structured beam, is illuminated and the structure pattern is imaged onto the substrate by means of the structured beam, producing a pattern image, namely, a spatial distribution of irradiation over the substrate. The direction of incidence of said beam onto the mask is varied through a sequence of inclinations with respect to the normal axis to the mask, the sequence of inclinations being adapted to merge those exposure pattern components which result from neighboring windows of the structure pattern, the exposure with respect to the sequence of inclinations superposing into a spatial distribution of exposure dose on the substrate, said distribution exceeding the specific minimum exposure dose of said resist material within only one or more regions of the substrate field, said region(s) forming the exposure pattern. The center of curvature of the substrate field is positioned to align with the pattern center on the mask. The windows of the structure pattern are arranged in a manner that along each radius from the pattern center, the radial spacing of said windows decreases with increasing radius from the pattern center; preferably, the windows have uniform area.