Patent ID: 7265055

Claim:
A method of chemically-mechanically polishing a substrate, which method comprises: (i) contacting a substrate comprising at least one layer of ruthenium and at least one layer of copper with a polishing pad and a chemical-mechanical polishing composition comprising: (a) an abrasive consisting of α-alumina treated with a negatively-charged polymer or copolymer, (b) hydrogen peroxide, (c) an organic acid, (d) at least one heterocyclic compound, wherein the at least one heterocyclic compound comprises at least one nitrogen atom, (e) a phosphonic acid, and (f) water, (ii) moving the polishing pad relative to the substrate, and (iii) abrading at least a portion of the substrate to polish the substrate, wherein the pH of the water and any components dissolved or suspended therein is about 6 to about 12, wherein the at least one layer of ruthenium and at least one layer of copper are in electrical contact and are in contact with the polishing composition, wherein the difference between the open circuit potential of copper and the open circuit potential of ruthenium in the water and any components dissolved or suspended therein is about 50 mV or less, and wherein a selectivity for polishing copper as compared to ruthenium is about 2 or less.