A method for fracturing or mask data preparation is disclosed, in which a set of shots is determined, where each shot will direct a circular or nearly-circular dosage pattern to a surface, where each shot comprises a shot dosage, and in which the set of shots is output. A method for forming patterns on a surface using charged particle beam lithography is also disclosed, in which a stencil is provided comprising one or more circular apertures, and where a plurality of circular patterns of different sizes are formed on the surface using a single aperture, by varying the shot dosage.