The use of smooth post-ECP topography (instead of final chip topography) as an objective during dummy filling enables a computationally efficient model-based dummy filling solution for copper while maintaining solution quality. A layout can be divided into tiles and the "case" of each tile identified. Exemplary cases can include conformal fill, over fill, super fill, or super/over fill (if the ECP model cannot distinguish between super and over fill cases). One or more undesired tile cases can be converted to a desired tile case. Then, a height difference between tiles can be minimized. Dummy features can be inserted in the layout to perform the conversion and to minimize the height difference between tiles. Minimizing the CMP-effective density difference between tiles with ECP considerations can be performed to further improve planarization.