Polishing compositions and methods for selectively polishing silicon nitride over silicon oxide films

摘要

Stable aqueous polishing compositions that can selectively polish silicon nitride (SiN) films and nearly stop (or polish at very low rates) on silicon oxide films are provided herein. The compositions comprise an anionic abrasive, a nitride removal rate enhancer containing a carboxyl or carboxylate group, water, and optionally, an anionic polymer. The synergistic combination of anionic (negatively charged) abrasives and the nitride removal rate enhancer provide beneficial charge interactions with the dielectric films during CMP, a high SiN rate and selectivity enhancement (over oxide), and stable colloidal dispersed slurries.

主权项

1. A polishing composition, comprising:
a) an anionic abrasive selected from the group consisting of alumina, silica, titania, ceria, zirconia, co-formed products thereof, and mixtures thereof; b) a nitride removal rate enhancer comprising a carboxylic acid or a carboxyl/carboxylate group for increasing silicon nitride rates; c) water; and (d) optionally, an anionic polymer; wherein the polishing composition has a pH range of about 2 to about 6.5, and wherein the anionic abrasive has a zeta potential in the range of 0 mV to −100 mV across the entire pH range, wherein the anionic abrasive comprises terminal groups of generic formulation (I):
—Ox—Y—(CH2)z-Anionic group,  (I) wherein x and z are integers, and Y is selected from the group consisting of Aluminum (Al), Silicon (Si), Titanium (Ti), Cerium (Ce), Zirconium (Zr), co-formed products thereof, and mixtures thereof, and the Anionic group is an acid, wherein the polishing composition has a zeta potential in the range of −5 mV to −100 mV, and wherein the composition exhibits a first rate of removal of silicon nitride, and a second rate of removal of silicon oxide, and a ratio of said first rate to said second rate is 9 or higher.