Compositions and methods for polishing silicon nitride materials
View Patent ↗The present invention provides a method for polishing silicon nitride-containing substrates. The method comprises abrading a surface of a silicon nitride substrate with a polishing composition, which comprises colloidal silica, at least one acidic component, and an aqueous carrier. The at least one acidic component has a pKa in the range of about 1 to 4.5. The 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.
1. 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.
2. The method of claim 1 wherein the pH of the polishing composition is not more than about 1 pH unit greater than the pKa of the at least one acidic component.
3. The method of claim 1 wherein the pH of the polishing composition is less than about 1 pH unit greater than the pKa of the at least one acidic component.
4. The method of claim 1 wherein the colloidal silica is present in the composition in an amount in the range of about 0.1 to about 4 percent by weight.
5. The method of claim 1 wherein the at least one acidic component is present in the polishing composition in an amount in the range of about 500 to about 2000 ppm.
6. A chemical-mechanical polishing (CMP) method for selectively removing silicon nitride in the presence of polysilicon in a substrate, the method comprising the steps of:
(a) abrading a surface of a substrate comprising silicon nitride and polysilicon 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 polysilicon.
7. The method of claim 6 wherein the pH of the polishing composition is not more than about 1 pH unit greater than the pKa of the at least one acidic component.
8. The method of claim 6 wherein the pH of the polishing composition is less than about 1 pH unit greater than the pKa of the at least one acidic component.
9. The method of claim 6 wherein the colloidal silica is present in the composition in an amount in the range of about 0.1 to about 4 percent by weight.
10. The method of claim 6 wherein the at least one acidic component is present in the polishing composition in an amount in the range of about 500 to about 2000 ppm.