Patent ID: 8759216

Claim:
A chemical-mechanical polishing (CMP) method for selectively removing silicon nitride in the presence of silicon oxide in a substrate, the method comprising the steps of: (a) abrading a surface of a substrate comprising silicon nitride and silicon oxide with a polishing composition including about 0.01 to about 15 percent by weight of colloidal silica, about 10 to about 100,000 ppm of at least one acidic component having a pKa in the range of about 1 to about 4.5, wherein the least one acidic component is selected from the group consisting of an organic phosphonic acid, an acidic heterocyclic compound, a salt thereof, and a combination thereof, and an aqueous carrier therefor, wherein the polishing composition has a pH in the range of about 0.5 pH units less than the pKa of the at least one acidic component to about 1.5 pH units greater than the pKa; wherein a relative rate of silicon nitride removal exceeds a rate for removal of silicon oxide.