DIAMOND-BASED SLURRIES WITH IMPROVED SAPPHIRE REMOVAL RATE AND SURFACE ROUGHNESS
The invention provides a chemical-mechanical polishing composition and a method of chemically-mechanically polishing a sapphire substrate. The composition contains a diamond abrasive and a pH adjuster. The method involves contacting the 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) diamond abrasive;
(b) pH adjusting compound;
(c) optionally, a polishing additive; and
(d) a liquid medium comprising water, a water soluble organic compound, or a combination thereof.
2 . The composition of claim 1 wherein the diamond abrasive has an average size of at least 1 μm.
3 . The composition of claim 1 wherein the diamond abrasive has an average size of about 2 μm to about 4 μm.
4 . The composition of claim 1 wherein the pH adjusting compound is an acid. The composition of claim 1 wherein the pH adjusting compound is a base.
6 . The composition of claim 1 wherein the liquid medium is a water soluble organic compound.
7 . The composition of claim 1 wherein the liquid medium is a glycol.
8 . The composition of claim 1 wherein the liquid medium is distilled water.
9 . The composition of claim 1 wherein the polishing additive is present.
10 . The composition of claim 9 wherein the polishing additive is selected from the group consisting of a surfactant, a polymer, a chelating agent or a complexing agent, and combinations thereof.
11 . The composition of claim 9 wherein the polishing additive is a copolymer of diallyl dimethyl ammonium chloride and acrylic acid.
12 . The composition of claim 9 wherein the polishing additive is maltol.
13 . The composition of claim 1 , further comprising a second diamond abrasive having a smaller average particle size from the diamond abrasive.
14 . A chemical-mechanical polishing method for polishing a sapphire substrate which method comprises:
(i) contacting a sapphire substrate with a polishing pad and the polishing composition of claim 1 :
(ii) moving the polishing pad and the polishing composition relative to the substrate to abrade at least a portion of the substrate to polish the substrate.