A method and apparatus for polishing or planarizing a substrate by a chemical mechanical polishing process. In one embodiment a method of processing a semiconductor substrate is provided. The method comprises positioning a substrate on a polishing apparatus comprising a polishing pad assembly, delivering a polishing slurry to a surface of the polishing pad assembly, polishing the substrate with the surface of the polishing pad assembly, monitoring the removal rate of material from a plurality of regions on the surface of the substrate, determining whether the plurality of regions on the surface of the substrate are polishing uniformly, and selectively delivering a polishing slurry additive to at least one region of the plurality of regions to obtain a uniform removal rate of material from the plurality of regions on the surface of the substrate, wherein the removal rate of material from the at least one region is different than at least one other region of the plurality of regions.