Polishing composition for nickel-phosphorous-coated memory disks
The invention provides a chemical-mechanical polishing composition containing wet-process silica, an oxidizing agent that oxidizes nickel-phosphorous, a chelating agent, polyvinyl alcohol, and water. The invention also provides a method of chemically-mechanically polishing a substrate, especially a nickel-phosphorous substrate, by contacting a substrate with a polishing pad and the chemical-mechanical polishing composition, moving the polishing pad and the polishing composition relative to the substrate, and abrading at least a portion of the substrate to polish the substrate.
1. A method of chemically-mechanically polishing a memory or rigid disk substrate, which method comprises:
(i) providing a memory or rigid disk substrate comprising at least one layer of nickel-phosphorous,
(ii) providing a polishing pad,
(iii) providing a polishing composition comprising:
(a) wet-process silica,
(b) an oxidizing agent that oxidizes nickel-phosphorous,
(c) a chelating agent,
(d) polyvinyl alcohol, wherein the polyvinyl alcohol has a degree of hydrolysis of about 90% or more,
(e) water,
wherein the polishing composition has a pH of about 1 to about 4,
(iv) contacting a surface of the substrate with the polishing pad and the polishing composition, and
(v) abrading at least a portion of the surface of the substrate to remove at least some nickel-phosphorous from the surface of the substrate and to polish the surface of the substrate.
2. The method of claim 1 , wherein the polishing composition comprises about 1 wt. % to about 10 wt. % of wet-process silica.
3. The method of claim 1 , wherein the oxidizing agent is hydrogen peroxide.
4. The method of claim 1 , wherein the chelating agent is glycine or alanine.
5. The method of claim 1 , wherein the polishing composition comprises about 0.1 wt. % to about 2 wt. % of the chelating agent.
6. The method of claim 1 , wherein the polyvinyl alcohol has a degree of hydrolysis of about 98% or more.
7. The method of claim 1 , wherein the polishing composition comprises about 0.1 wt. % to about 2 wt. % of polyvinyl alcohol.
8. The method of claim 1 , wherein the polishing composition has a pH of about 1 to about 3.
9. The method of claim 1 , wherein the substrate is a nickel-phosphorous-coated aluminum disk.
10. The method of claim 1 , wherein the wet-process silica has an average particle size of about 10 nm to about 80 nm.
11. The method of claim 10 , wherein the wet-process silica has an average particle size of about 10 nm to about 30 nm.
12. The method of claim 1 , wherein the polyvinyl alcohol has a molecular weight of about 8,000 g/mol to about 50,000 g/mol.
13. The method of claim 12 , wherein the polyvinyl alcohol has a molecular weight of about 13,000 g/mol to about 23,000 g/mol.
14. A method of chemically-mechanically polishing a memory or rigid disk substrate, which method comprises:
(i) providing a memory or rigid disk substrate,
(ii) providing a polishing pad,
(iii) providing the polishing composition comprising:
(a) wet-process silica,
(b) an oxidizing agent that oxidizes nickel-phosphorous,
(c) a chelating agent,
(d) polyvinyl alcohol, wherein the polyvinyl alcohol has a molecular weight of about 8,000 g/mol to about 50,000 g/mol,
(e) water,
wherein the polishing composition has a pH of about 1 to about 4, and wherein the polishing composition does not comprise a heterocyclic compound,
(iv) contacting a surface of the substrate with the polishing pad and the polishing composition, and
(v) abrading at least a portion of the surface of the substrate to remove at least some portion of the surface of the substrate so as to polish the surface of the substrate.