In one embodiment, the disclosure relates to a method and apparatus for inserting dummy patterns in sparsely populated portions of a metal layer. The dummy pattern counters the effects of variations of pattern density in a semiconductor layout which can cause uneven post-polish film thickness. An algorithm according to one embodiment of the disclosure determines the size and location of the dummy patterns based on the patterns in the metal layer by first surrounding the metal structure with small dummy pattern and then filling any remaining voids with large dummy patterns.