EXPOSURE METHOD AND TOOL

A method for forming a regularly repeating pattern on to a substrate comprising the steps of: applying a resist on a surface of a substrate to be processed; imprinting on the applied resist a pattern formed by exposing it to a beam of ultra violet ('UV') light, which has been caused to pass through a suitable mask delineating the pattern and then trough a focusing lens on to the resist, so as to cause chemical changes in the resist which makes it more or less soluble in a suitable developer solution; the imprinting step being carried out: in a repetitive series of discrete exposure steps using a mask held stationery with respect to the beam and the lens that represents only a small area of the total area of the substrate and using a single short pulse of UV radiation at each step to illuminate the mask, the radiation pulse having such an energy density at the substrate that it is below the threshold value for ablation of the resist; and the series of discrete exposure steps being repeated over the full area of the surface of a substrate, to give a full structure comprising a plurality of pixels, by moving the substrate in a direction parallel to one axis of the structure to be formed on the substrate and activating the pulsed mask illumination light source at the instant that the substrate has moved over a distance equivalent to a complete number of periods of the repeating pattern on the substrate; treating the exposed resist with a developer to cause either exposed regions (for positive resists) or unexposed regions (for negative resists) to be dissolved and subsequently washed away by the developer solution to reveal the pattern formed by the remaining resist; treating the substrate with a suitable chemical etching solution, reactive plasma or abrasive particles that removes the substrate in resist free areas; and removing remaining resist from the substrate with a suitable solvent to leave a finished patterned substrate. The invention further comprises a scanning exposure tool for carrying out the method as aforesaid.