Polishing composition for nickel-phosphorous memory disks

1. A method of chemically-mechanically polishing a nickel-phosphorous-coated aluminum substrate comprising:

(i) contacting a substrate with a polishing pad and a chemical-mechanical polishing composition comprising:

(a) fumed alumina particles,

(b) alpha alumina particles,

(c) substantially spherical, non-aggregated silica particles,

(d) about 10 ppm to about 200 ppm nonionic surfactant

(d) an oxidizing agent comprising 0.05 wt. % to about 0.3 wt. % of hydrogen peroxide, about 0.1 wt. % to about 0.5 wt. % potassium hydrogen peroxymonosulfate sulfate, and about 0.5 wt. % to about 1 wt. % sodium persulfate,

(e) a complexing agent, and

(f) water,

(ii) moving the polishing pad relative to the substrate with the chemical-mechanical polishing composition there between, and

(iii) abrading at least a portion of the substrate to polish the substrate, wherein the microwaviness and edge roll-off in the polished substrate is improved compared to substrates polished with identical polishing compositions, but having only one or two of the oxidizing agents.

2. The method of claim 1 , wherein the polishing composition comprises about 0.1 wt. % to about 3 wt. % of fumed alumina particles, about 0.1 wt. % to about 1 wt. % of alpha alumina particles, and about 0.5 wt. % to about 5 wt. % of substantially spherical, non-aggregated silica particles.

3. The polishing composition of claim 1 , wherein the nonionic surfactant is a copolymer surfactant comprising siloxane units, ethylene oxide units, and propylene oxide units.

4. The method of claim 1 , wherein the polishing composition comprises about 0.1 wt. % to about 5 wt. % complexing agent.

5. The method of claim 1 , wherein the complexing agent is an amino acid.

6. The method of claim 1 , wherein the complexing agent is glycine.

7. The method of claim 1 , wherein the substrate comprises a nickel-phosphorous-coated aluminum disk.

8. The method of claim 7 , wherein the disk is a memory disk.