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:
at least one oxidizing agent;
a total amount of less than 0.2 wt.-% of abrasive particles based on a total weight of the aqueous suspension, wherein the abrasive particles have a Mohs hardness of less than 6; and
aluminum nitrate.
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 at least one oxidizing agent 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 abrasive particles comprise alumina particles.
6 . The aqueous suspension of claim 5 , wherein the alumina particles comprise γ-AlOOH particles.
7 . 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.
8 . The method of claim 7 , wherein the substrate does not exceed a temperature of 60° C. during abrading.
9 . The method of claim 7 , 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.
10 . The method of claim 9 , wherein the substrate is contacted with the aqueous suspension within fourteen days of reducing the pH.
11 . A method for preparing an aqueous suspension, comprising:
(i) adding aluminum nitrate to the aqueous suspension comprising abrasive particles; and
(ii) adding an aqueous solution of at least one oxidizing agent to the aqueous suspension,
wherein the abrasive particles have a Mohs hardness of less than 6, and
wherein the aqueous suspension contains less than 0.2 wt.-% of the abrasive particles based on a total weight of the aqueous suspension.
12 . The method of claim 11 , further comprising, prior to adding the aluminum nitrate, filtering the aqueous suspension.
13 . The method of claim 11 , further comprising, prior to adding the aqueous solution, filtering the aqueous solution.
14 . The method of claim 11 , wherein the aqueous suspension has a pH value in a range from 2 to 5 at 23° C.
15 . The method of claim 11 , wherein the step (i) and the step (ii) are sequentially carried out.
16 . A method comprising:
storing an aqueous suspension having a pH ranging from 3 to 5;
reducing the pH of the aqueous suspension to range from 2 to 2.5; and
using the aqueous suspension having the pH ranging from 2 to 2.5 within fourteen days.
17 . The method of claim 16 , wherein the aqueous suspension comprises:
at least one oxidizing agent;
a total amount of less than 0.2 wt.-% of abrasive particles based on a total weight of the aqueous suspension, wherein the abrasive particles have a Mohs hardness of less than 6; and
aluminum nitrate.
18 . The method of claim 16 , wherein the aqueous suspension is stored for at least 1 year.
19 . The method of claim 16 , wherein the pH of the aqueous suspension is reduced to 2.3.
20 . The method of claim 16 , wherein the aqueous suspension having the pH ranging from 2 to 2.5 is used in a single-type or batch-type chemical mechanical planarization method.