Patent ID: 8592315

Claim:
A method of chemical mechanical polishing a substrate, wherein the substrate comprises: a first stepped portion having an upper face; and a first layer on the substrate, the first layer including a stepped portion, the stepped portion formed over, and conforming to, the first stepped portion, the method comprising: performing a first polishing process on the stepped portion of the first layer using an initial slurry composition including about 2 to about 3 percent by weight of a surfactant having an anionic polymer that reduces a chemical polishing rate of the first layer and having a pH value at which a zeta potential of the first layer is negative, wherein the first polishing process reduces the thickness of the first layer until stopping of the polishing is initiated by a self-stopping characteristic, to planarize the first layer, the planarized first layer covering the upper face of the first stepped portion; and performing a second polishing process on the planarized first layer until the upper face of the first stepped portion is exposed, wherein the second polishing process is performed using a subsequent slurry composition comprising about 0.001 to about 2 percent by weight of a surfactant including an anionic polymer, the subsequent slurry composition having a pH value at which a zeta potential of the planarized first layer is negative, wherein the concentration of the surfactant in the subsequent slurry composition is lower than the concentration of the surfactant used in the initial slurry composition such that only the first polishing process is subject to the self-stopping characteristic.