Aqueous silica slurry compositions for use in shallow trench isolation and methods of using them
The present invention provides aqueous CMP polishing compositions comprising a from 0.5 to 30 wt. %, based on the total weight of the composition of a dispersion of a plurality of elongated, bent or nodular silica particles which contain a cationic nitrogen atom, and from 0.001 to 0.5 wt. %, preferably from 10 to 500 ppm, of a cationic copolymer of a diallylamine salt having a cationic amine group, such as a diallylammonium halide, or a diallylalkylamine salt having a cationic amine group, such as a diallylalkylammonium salt, or mixtures of the copolymers, wherein the compositions have a pH of from 1 to 4.5. Preferably, the cationic copolymer of a diallylamine salt having a cationic amine group comprises a copolymer of diallylammonium chloride and sulfur dioxide and the copolymer of the diallylalkylamine salt having a cationic amine group comprises a copolymer of diallylmonomethylammonium halide, e.g. chloride, and sulfur dioxide. The slurry compositions demonstrate good oxide selectivity in the CMP polishing of pattern wafers having nitride and silicon patterns.
1. An aqueous chemical mechanical planarization polishing composition comprising a dispersion of a plurality of cationic elongated colloidal silica particles which contain a cationic nitrogen atom with a dispersion of spherical colloidal silica particles, wherein colloidal silica particles have a weight average size of 25 nm to 80 nm, and from 10 to 20 ppm of a cationic copolymer of diallylammonium chloride and sulfur dioxide, a cationic copolymer of diallylmonomethylammonium chloride and sulfur dioxide, or mixtures thereof, wherein the cationic copolymers have a weight average molecular weight of 2000 to 12,000, and the compositions have a pH of 2.5 to 4 and, further wherein, the amount of the dispersion of the cationic elongated colloidal silica particles ranges from 1 to 25 wt %, all weights based on the total weight of the composition.
2. The aqueous chemical mechanical planarization polishing composition as claimed in claim 1 , wherein the dispersion of the cationic elongated colloidal silica particles has for the average particle an aspect ratio of longest dimension to the diameter which is perpendicular to the longest dimension of 1.8:1 to 3:1.
3. The aqueous chemical mechanical planarization polishing composition as claimed in claim 1 , comprising a mixture of a dispersion of the cationic elongated colloidal silica particles and a dispersion of spherical colloidal silica particles, wherein the amount of the dispersion of the cationic elongated colloidal silica particles ranges from 80 to 99.9 wt. %, based on the total solids weight of the colloidal silica particles in the composition.
4. The chemical mechanical planarization polishing composition as claimed in claim 1 , wherein the cationic copolymer of diallylammonium chloride and sulfur dioxide comprises 45 to 55 mole % of the diallylammonium chloride having a cationic amine group and 45 to 55 mole % of the sulfur dioxide.
5. The chemical mechanical planarization polishing composition as claimed in claim 1 , wherein the cationic copolymer of diallylmonomethylammonium chloride and sulfur dioxide comprises 45 to 55 mole % of the diallylmonomethylammonium chloride having a cationic amine group and 45 to 55 mole % of the sulfur dioxide.
6. The chemical mechanical planarization polishing composition as claimed in claim 1 , wherein the amount of the dispersion of the cationic elongated colloidal silica particles ranges from 1 to 20 wt %.