Polishing composition and method for high silicon nitride to silicon oxide removal rate ratios
View Patent ↗The invention provides a chemical-mechanical polishing composition comprising a cationic abrasive, a cationic polymer, an inorganic halide salt, and an aqueous carrier. The invention further provides a method of chemically-mechanically polishing a substrate with the aforementioned polishing composition. The polishing composition exhibits selectivity for removal of silicon nitride over removal of silicon oxide and polysilicon.
1. A chemical-mechanical polishing (CMP) method for polishing a substrate, the method comprising the steps of:
(a) contacting a surface of a substrate comprising silicon nitride, silicon dioxide, and polysilicon, with a polishing pad and a CMP composition having a pH of about 7 or less, the CMP composition comprising a cationic abrasive, a cationic polymer, an inorganic halide salt, an aqueous carrier;
(b) causing relative motion between the polishing pad and the substrate with a portion of the CMP composition therebetween to selectively abrade silicon nitride from the surface relative to silicon dioxide and polysilicon.
2. The method of claim 1 wherein the cationic abrasive is selected from the group consisting of alumina, titania, zirconia, ceria, and doped silica.
3. The method of claim 1 wherein the cationic polymer is selected from the group consisting of a cationic homopolymer, a cationic copolymer comprising at least one cationic monomer and at least one nonionic monomer, and a combination thereof.
4. The method of claim 1 wherein the cationic abrasive is present in the composition in an amount in the range of about 0.01 to about 5 percent by weight.
5. The method of claim 1 wherein the cationic polymer is present in the composition in an amount in the range of about 0.1 to about 500 ppm.
6. The method of claim 1 wherein the inorganic halide salt is present in the composition in an amount in the range of about 100 to about 1000 ppm.
7. The method of claim 1 wherein the CMP composition further comprises an aminocarboxylic acid.
8. A chemical-mechanical polishing (CMP) method for selectively abrading silicon nitride in the presence of silicon dioxide, the method comprising the steps of
(a) contacting a surface of a substrate comprising silicon nitride and silicon dioxide with a polishing pad and a CMP composition having a pH of about 7 or less, the CMP composition comprising a cationic abrasive, a cationic polymer, an inorganic halide salt, an aqueous carrier;
(b) causing relative motion between the polishing pad and the substrate with a portion of the CMP composition therebetween to abrade silicon nitride from the surface at a removal rate in the range of about 6 to about 60 times the rate at which silicon dioxide is abraded from the surface.
9. The method of claim 8 wherein the composition further comprises an aminocarboxylic acid.
10. A chemical-mechanical polishing (CMP) method for selectively abrading silicon nitride in the presence of polysilicon, the method comprising the steps of:
(a) contacting a surface of a substrate comprising silicon nitride and polysilicon with a polishing pad and a CMP composition having a pH of about 7 or less, the CMP composition comprising a cationic abrasive, a cationic polymer, an inorganic halide salt, an aqueous carrier;
(b) causing relative motion between the polishing pad and the substrate with a portion of the CMP composition therebetween to abrade silicon nitride from the surface at a removal rate exceeding the rate at which polysilicon is abraded from the surface.
11. The method of claim 10 wherein the composition further comprises an aminocarboxylic acid.