Compositions and methods for selective polishing of silicon nitride materials
The present invention provides an acidic aqueous polishing composition suitable for polishing a silicon nitride-containing substrate in a chemical-mechanical polishing (CMP) process. The composition, at point of use, preferably comprises about 0.01 to about 2 percent by weight of at least one particulate ceria abrasive, about 10 to about 1000 ppm of at least one non-polymeric unsaturated nitrogen heterocycle compound, 0 to about 1000 ppm of at least one cationic polymer, optionally, 0 to about 2000 ppm of at least one polyoxyalkylene polymer, and an aqueous carrier therefor. The cationic polymer preferably is selected from a poly(vinylpyridine) polymer, a quaternary ammonium-substituted acrylate polymer, a quaternary ammonium-substituted methacrylate polymer, or a combination thereof. Methods of polishing substrates and of selectively removing silicon nitride from a substrate in preference to removal of polysilicon using the compositions are also provided.
1. A chemical-mechanical polishing (CMP) method for selectively removing silicon nitride from a surface of a substrate in preference to removal of polysilicon, the method comprising the steps of:
(a) contacting a surface of a silicon nitride- and polysilicon-containing substrate with a polishing pad and an acidic aqueous CMP composition; and
(b) causing relative motion between the polishing pad and the substrate while maintaining a portion of the CMP composition in contact with the surface between the pad and the substrate for a time period sufficient to abrade silicon nitride from the surface;
wherein the CMP composition comprises:
(i) about 0.1 to about 0.3 percent by weight of a calcined ceria abrasive;
(ii) about 10 to about 1000 ppm of at least one non-polymeric unsaturated nitrogen heterocycle compound;
(iii) 10 to about 1000 ppm of at least one cationic polymer, wherein the cationic polymer comprises a poly(vinylpyridine) polymer, a quaternary ammonium-substituted acrylate polymer, a quaternary ammonium-substituted methacrylate polymer, or a combination of any of the foregoing cationic polymers;
(iv) 200 to about 2000 ppm of at least one polyoxyalkylene polymer, wherein the polyoxyalkylene polymer comprises a poly(ethylene glycol) polymer, a poly(ethylene glycol)-co-poly(propylene glycol) block copolymer, or a combination thereof; and
(v) an aqueous carrier therefor, wherein the CMP composition has a pH in the range of about 3 to about 5.
2. The method of claim 1 wherein the polyoxyalkylene polymer comprises a poly(ethylene glycol) polymer comprising an average number of ethylene glycol monomer units in the range of about 300 to about 1500.
3. The method of claim 1 wherein the non-polymeric unsaturated nitrogen heterocycle compound comprises a pyridine compound.
4. The method of claim 1 wherein the non-polymeric unsaturated nitrogen heterocycle compound comprises a pyridinium compound.
5. Then method of claim 1 wherein the non-polymeric unsaturated nitrogen heterocycle compound comprises 4,4′-trimethylenedipyridine.
6. The method of claim 1 wherein the surface of the substrate also comprises silicon dioxide.