Polishing composition for nickel phosphorous memory disks
The invention provides a chemical-mechanical polishing composition comprising alpha alumina, fumed alumina, silica, an oxidizing agent that oxidizes nickel-phosphorous, oxalic acid, optionally, tartaric acid, optionally, a nonionic surfactant, optionally, a biocide, and water. The invention also provides a method of chemically-mechanically polishing a substrate comprising 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 chemical-mechanical polishing composition comprising:
(a) alpha alumina,
(b) fumed alumina,
(c) silica,
(d) an oxidizing agent that oxidizes nickel-phosphorous,
(e) about 0.1 wt.% to about 2 wt.% of oxalic acid,
(f) about 0.1 wt% to 0.75 wt.% tartaric acid,
(g) a nonionic surfactant,
(h) optionally, a biocide, and
(i) water,
wherein the polishing composition has a pH of about 2 to about 4.
2. The polishing composition of claim 1 , wherein the polishing composition comprises about 0.5 wt.% to about 2 wt.% of alpha alumina, about 0.1 wt.% to about 1 wt.% of fumed alumina, and about 0.5 wt.% to about 2 wt.% of silica.
3. The polishing composition of claim 1 , wherein the alpha alumina has an average particle size of about 300 nm to about 800 nm.
4. The polishing composition of claim 3 , wherein the alpha alumina has an average particle size of about 400 nm to about 600 nm.
5. The polishing composition of claim 1 , wherein the fumed alumina has an average particle size of about 75 nm to about 150 nm.
6. The polishing composition of claim 1 , wherein the silica has an average particle size of about 20 nm to about 120 nm.
7. The polishing composition of claim 1 , wherein the oxidizing agent is hydrogen peroxide.
8. The polishing composition of claim 1 , wherein the polishing composition comprises about 1 ppm to about 100 ppm of the nonionic surfactant.
9. The polishing composition of claim 1 , wherein the pH of the polishing composition is about 2 to about 3.