Auxiliary structural features with sub-resolution size

A method for reducing corner rounding and image reduction in an image on a substrate by illuminating a photolithographic mask and projecting light, which passes through the photolithographic mask on the substrate is imaged using an optical projection system, wherein the photolithographic mask, a mask structure which comprises a plurality of rectangular shaped openings (504) to form dense array structures as imageable structural features (502) with at least one corner and linear structural features (510) that are inserted in the mask pattern for each of the openings (504) in such a way that - the linear structural features (510) perpendicular to the imageable structural features (502) extend, - each linear structural feature (510) connects adjacent imageable structural features (502) - the ends of the linear structural features (510) extending from the corners of the openings (504) extending in the dense array structure and - the linear structural features (510) have a line width that is less than a minimum resolution of the optical ...