A method for reducing layer overlay errors by synchronizing the density of mask material in the frame area across the masks in a set is disclosed. An exemplary method includes creating a mask design database corresponding to a mask and containing a die area with one or more dies and a frame area outside the die area. Fiducial features within the frame area are identified, and from the fiducial features, an idle frame area is identified. A reference mask design, which corresponds to a reference mask configured to be aligned with the mask, is used to determine a reference density for the idle frame area. The idle frame area of the mask design database is modified to correspond to the reference density. The modified mask design database is then available for further use including manufacturing the mask.