SUSPENSION FOR CHEMICAL MECHANICAL PLANARIZATION (CMP) AND METHOD EMPLOYING THE SAME
The present disclosure relates to aqueous suspensions suitable for chemical mechanical planarization (CMP), the use of aqueous suspensions and a method of CMP using aqueous suspensions. The suspensions and method can be used for CMP of silicon carbide surfaces.
1 . An aqueous suspension comprising:
(a) one or more metal salts of permanganic acid;
(b) zirconia nanoparticles;
(c) alumina nanoparticles; and
(d) one or more salts of nitric acid.
2 . The aqueous suspension of claim 1 , further comprising at least one pH adjusting agent and/or at least one pH buffering agent.
3 . The aqueous suspension of claim 1 , wherein the aqueous suspension has a pH value in a range from 2 to 5.
4 . The aqueous suspension of claim 1 , wherein the one or more metal salts of permanganic acid is selected from the group consisting of LiMnO 4 , KMnO 4 , NaMnO 4 , and mixtures thereof.
5 . The aqueous suspension of claim 1 , wherein the zirconia nanoparticles comprise ZrO 2 .
6 . The aqueous suspension of claim 1 , wherein the alumina nanoparticles comprise colloidal alumina particles.
7 . The aqueous suspension of claim 6 , wherein the colloidal alumina particles comprise γ-AlOOH particles and/or γ-Al 2 O 3 particles.
8 . The aqueous suspension of claim 1 , wherein the one or more salts of nitric acid comprises Al(NO 3 ) 3 .
9 . A method of chemically-mechanically planarizing a substrate, comprising:
(i) contacting the substrate with an aqueous suspension of claim 1 ;
(ii) moving the aqueous suspension with a polishing pad relative to the substrate; and
(iii) abrading at least a portion of the substrate to polish the substrate.
10 . The method of claim 9 , wherein the substrate does not exceed a temperature of 60° C. during abrading.
11 . The method of claim 9 , further comprising, before contacting the substrate with the aqueous suspension, reducing a pH of the aqueous suspension to a range of 2 to 2.5.
12 . A method for preparing an aqueous suspension, comprising:
(i) adding aluminum nitrate to the aqueous suspension comprising alumina nanoparticles and zirconia nanoparticles; and
(ii) adding an aqueous solution of one or more metal salts of permanganic acid to the aqueous suspension.
13 . The method of claim 12 , further comprising, prior to the adding the aluminum nitrate, filtering the aqueous suspension.
14 . The method of claim 12 , further comprising, prior to the adding the aqueous solution, filtering the aqueous solution of one or more metal salts of permanganic acid.
15 . The method of claim 12 , wherein the aqueous suspension has a pH value in a range from 2 to 5 at 23° C.
16 . The method of claim 12 , wherein the step (i) and the step (ii) are sequentially carried out.