Chemical-mechanical polishing of metals in an oxidized form
View Patent ↗The invention provides a method for polishing a substrate comprising a metal in an oxidized form, the method comprising the steps of: (a) providing a substrate comprising a metal in an oxidized form, (b) contacting a portion of the substrate with a chemical-mechanical polishing system comprising: (i) a polishing component, (ii) a reducing agent, and (iii) a liquid carrier, and (c) abrading at least a portion of the metal in an oxidized form to polish the substrate. The reducing agent can be selected from the group consisting of 3-hydroxy-4-pyrones, α-hydroxy-γ-butyrolactones, ascorbic acid, borane, borohydrides, dialkylamine boranes, formaldehyde, formic acid, hydrogen, hydroquinones, hydroxylamine, hypophosphorous acid, phosphorous acid, a metal or metal ions in an oxidation state having a standard redox potential that is less than the standard redox potential of the metal in an oxidized form, trihydroxybenzenes, solvated electrons, sulfurous acid, salts thereof, and mixtures thereof.
1. A method for polishing a substrate comprising a metal in an oxidized form, the method comprising the steps of:
(a) providing a substrate comprising a metal in an oxidized form, wherein the metal is a noble metal selected from the group consisting of platinum, iridium, ruthenium, rhodium, palladium, silver, osmium, gold, and combinations thereof,
(b) contacting a portion of the substrate with a chemical-mechanical polishing system comprising:
(i) a polishing component selected from the group consisting of an abrasive, a polishing pad, and a combination thereof,
(ii) about 0.1 to about 1 wt. % of a reducing agent based on the weight of the liquid carrier and any components dissolved or suspended therein, wherein the reducing agent is ascorbic acid, and
(iii) a liquid carrier, and
(c) abrading at least a portion of the metal in an oxidized form to polish the substrate.
2. The method of claim 1 , wherein the chemical-mechanical polishing system comprises about 0.1 to about 0.5 wt. % ascorbic acid based on the weight of the liquid carrier and any components dissolved or suspended therein.
3. The method of claim 1 , wherein the polishing system has a pH of about 1 to about 7.
4. The method of claim 3 , wherein the chemical-mechanical polishing system has a pH of about 2 to about 5.
5. The method of claim 1 , wherein the oxidized form is selected from the group consisting of oxides, nitrides, borides, sulfides, and mixtures thereof.
6. The method of claim 5 , wherein the oxidized form is an oxide, and the metal in an oxidized form has a molecular formula M x O y in which M represents the metal and x and y represent integers, where y is greater than or equal to x.
7. The method of claim 6 , wherein the metal in an oxidized form is iridium oxide.
8. The method of claim 1 , wherein the chemical-mechanical polishing system comprises an abrasive suspended in the liquid carrier, and the abrasive comprises a metal oxide selected from the group consisting of alumina, silica, ceria, zirconia, titania, germania, co-formed products thereof, and combinations thereof.
9. The method of claim 8 , wherein the abrasive comprises silica, fumed alumina, or a combination thereof.
10. The method of claim 8 , wherein the abrasive comprises α-alumina.
11. The method of claim 10 , wherein the abrasive further comprises fumed alumina.
12. The method of claim 10 , wherein α-alumina comprises about 60 wt. % or more of the abrasive based on the total weight of the abrasive.
13. The method of claim 11 , wherein α-alumina comprises about 60 wt. % or more of the abrasive based on the total weight of the abrasive.
14. The method of claim 1 , wherein the chemical-mechanical polishing system further comprises a complexing agent.
15. The method of claim 1 , wherein the chemical-mechanical polishing system further comprises a pH buffering agent.
16. The method of claim 1 , wherein the chemical-mechanical polishing system further comprises a surfactant.
17. The method of claim 1 , wherein the liquid carrier is water.
18. The method of claim 17 , wherein the oxidized form is selected from the group consisting of oxides, nitrides, borides, sulfides, and mixtures thereof.
19. The method of claim 18 , wherein the oxidized form is an oxide, and the metal in an oxidized form has a molecular formula M x O y in which M represents the metal and x and y represent integers, where y is greater than or equal to x.
20. The method of claim 19 , wherein the metal in an oxidized form is iridium oxide.
21. The method of claim 17 , wherein the chemical-mechanical polishing system comprises an abrasive suspended in the liquid carrier, and the abrasive comprises a metal oxide selected from the group consisting of alumina, silica, ceria, zirconia, titania, germania, co-formed products thereof, and combinations thereof.
22. The method of claim 21 , wherein the abrasive comprises silica, fumed alumina, or a combination thereof.
23. The method of claim 21 , wherein the abrasive comprises α-alumina.
24. The method of claim 23 , wherein the abrasive further comprises fumed alumina.
25. The method of claim 23 , wherein α-alumina comprises about 60 wt. % or more of the abrasive based on the total weight of the abrasive.
26. The method of claim 24 , wherein α-alumina comprises about 60 wt. % or more of the abrasive based on the total weight of the abrasive.
27. The method of claim 17 , wherein the chemical-mechanical polishing system further comprises a complexing agent.
28. The method of claim 17 , wherein the chemical-mechanical polishing system further comprises a pH buffering agent.
29. The method of claim 17 , wherein the chemical-mechanical polishing system further comprises a surfactant.
30. The method of claim 17 , wherein the chemical-mechanical polishing system has a pH of about 2 to about5.