Iodate-containing chemical-mechanical polishing compositions and methods

1. A chemical-mechanical polishing composition for polishing a substrate comprising:

(a) about 0.25 wt. % to about 0.75 wt. % colloidal silica abrasive having an average particle size of about 25 nm to about 80 nm,

(b) about 0.05 wt. % to about 0.1 wt. % iodate ion,

(c) about 0.05 wt. % to about 0.1 wt. % 1H-1,2,3-benzotriazole, and

(d) a liquid carrier comprising water,

wherein the pH of the polishing composition is 2.4-2.8.

2. The polishing composition of claim 1 , wherein the silica abrasive is present in an amount of about 0.25 wt. % to about 0.5 wt. %.

3. A method of chemically-mechanically polishing a substrate, which method comprises:

(a) providing a substrate,

(b) contacting the substrate with a polishing pad and a chemical-mechanical polishing composition comprising:

(i) about 0.25 wt. % to about 0.75 wt. % colloidal silica abrasive having an average particle size of about 25 nm to about 80 nm,

(ii) about 0.05 wt. % to about 0.1 wt. % iodate ion,

(iii) about 0.05 wt. % to about 0.1 wt. % 1H-1,2,3-benzotriazole, and

(iv) a liquid carrier comprising water,

wherein the pH of the polishing composition is 2.4-2.8,

(c) moving the polishing pad relative to the substrate with the chemical-mechanical polishing composition therebetween, and

(d) abrading at least a portion of the substrate to polish the substrate.

4. The method of claim 3 , wherein the silica abrasive is present in an amount of about 0.25 wt. % to about 0.5 wt. %.

5. The method of claim 3 , wherein the substrate comprises a metal layer.

6. The method of claim 5 , wherein the metal layer comprises tantalum.

7. The method of claim 6 , wherein the metal layer further comprises copper.