Patent ID: 7468784

Claim:
A method for forming an optical or magnetic memory medium or a template for making such memory media, comprising the steps of: suspending an essentially flat substrate rotatably about an axis, which substrate is provided with a surface layer of a resist material; arranging a particle beam source to expose the surface layer to a beam; rotating the substrate such that the particle beam forms a groove in the surface layer by exposure to a predetermined degree, which groove has a width on the order of 1-100 nm; and controlling the position of the particle beam and the axis relative to each other during rotation of the substrate about the axis, so that the particle beam and the axis are held at an essentially constant distance from each other while the substrate is rotated several times about the axis, and so that at least a part of the groove is subjected to more than one exposure to the particle beam, thereby forming a circular groove which is concentric with the axis and which is formed as a sum of said more than one exposure, which sum corresponds to said predetermined degree of exposure, wherein the particle beam and the axis are controlled relative to each other to form a plurality of grooves which are concentric with the axis, each groove being exposed to essentially said pretermined degree of exposure, independently of radial distance of the groove to the axis, and wherein the particle beam has an intensity which is controlled so as to be a function of radial distance of the groove to the axis.