Composition and method for silicon nitride CMP

1. A chemical-mechanical polishing composition for polishing a silicon nitride containing substrate, the polishing composition comprising:

an aqueous carrier;

cationic silica particles dispersed in the aqueous carrier, the cationic silica abrasive particles having a zeta potential of at least 10 mV in the polishing composition;

a polishing additive comprising polyether amine having a weight average molecular weight of about 500 g/mol or less, wherein the polyether amine is of Formula (I):

wherein R is a C 1 -C 6 alkyl group and x, y, and z independently are integers from 0 to 15, wherein the polishing additive is present in the polishing composition at a concentration in a range from about 0.07 mM to about 0.25 mM; and

wherein the polishing composition has a pH of about 6 to about 8.

2. The polishing composition of claim 1 , wherein the cationic silica abrasive particles have a surface which has been treated with a quaternary aminosilane, dipodal aminosilane, or combinations thereof.

3. The polishing composition of claim 1 , wherein the cationic silica abrasive particles comprise colloidal silica particles having a permanent positive charge of at least 20 mV at a pH of greater than about 6.

4. The polishing composition of claim 3 , wherein the polishing composition has a pH of about 7.

5. The polishing composition of claim 1 , wherein the cationic silica abrasive particles have a mean particle size of about 20 nm to about 80 nm.