An exposure method includes designing a target pattern to be formed on a substrate, producing a first dose map having first dose values of beams of energy, e.g., electron beams, creating from the first dose map a second dose map having second dose values different from the first dose values, and irradiating regions of a layer of photoresist on the substrate with overlapping beams to expose the regions to doses of energy having values based on the second dose values. The photoresist layer may then be developed and used an etch mask. The etch mask may be used to etch a mask layer on a transparent substrate to form a reticle.