GST CMP slurries
The present invention provides chemical-mechanical polishing (CMP) compositions suitable for polishing a substrate comprising a germanium-antimony-tellurium (GST) alloy. The CMP compositions of the present invention are aqueous slurries comprising a particulate abrasive, a water-soluble surface active agent, a complexing agent, and a corrosion inhibitor. The ionic character of the surface active material (e.g., cationic, anionic, or nonionic) is selected based on the zeta potential of the particulate abrasive. A CMP method for polishing a GST alloy-containing substrate utilizing the composition is also disclosed.
1. An aqueous chemical-mechanical polishing (CMP) composition for polishing germanium-antimony-tellurium (GST) alloys, the composition comprising an aqueous carrier containing:
(a) a particulate abrasive selected from the group consisting of a colloidal silica abrasive and ceria abrasive;
(b) a water soluble surface active material;
(c) an amino acid corrosion inhibitor; and
(d) a complexing agent;
wherein the surface active material is selected based on the zeta potential of the particulate abrasive, such that when the abrasive has a positive zeta potential, the surface active material comprises a cationic material, and when the particulate abrasive has a negative zeta potential, the surface active material comprises an anionic material, a nonionic material, or a combination thereof.
2. The CMP composition of claim 1 wherein the composition is substantially free of oxidizing agents.
3. The CMP composition of claim 1 wherein the amino acid corrosion inhibitor comprises lysine.
4. The CMP composition of claim 1 wherein the complexing agent comprises a phosphonic acid compound.
5. The CMP composition of claim 4 wherein the phosphonic acid comprises 1-hydroxyethylidene-1,1,-diphosphonic acid.
6. The CMP composition of claim 1 wherein the particulate abrasive comprises wet-processed ceria.
7. The CMP composition of claim 1 wherein the particulate abrasive comprises ceria and the composition has a pH in the range of about 4 to 5.
8. The CMP composition of claim 1 wherein the particulate abrasive comprises a colloidal silica, and the composition has a pH in the range of about 2 to 3.
9. The CMP composition of claim 1 wherein the particulate abrasive comprises an aminosilane surface-treated colloidal silica having a positive zeta potential.
10. The CMP composition of claim 1 wherein the particulate abrasive comprises ceria or an aminosilane surface-treated colloidal silica having a positive zeta potential, and the water soluble surface active material comprises a poly(methacryloyloxyethyl trimethylammonium)halide.
11. The CMP composition of claim 1 wherein the particulate abrasive comprises a colloidal silica having a negative zeta potential, and the water soluble surface active material comprises a poly(acrylic acid), a polyacrylamide, or a combination thereof.
12. The CMP composition of claim 1 , wherein the particulate abrasive has an average particle size in the rage of about 10 to about 200 nm.
13. The CMP composition of claim 1 , wherein the particulate abrasive is present in the composition at a concentration in the range of about 0.01 to about 10 percent by weight (wt %).
14. The CMP composition of claim 1 , wherein the water soluble surface active material is present in the composition at a concentration in the range of about 10 to about 10,000 parts-per-million (ppm).
15. The CMP composition of claim 1 , wherein the amino acid corrosion inhibitor is present in the composition at a concentration in the range of about 0.01 to about 2 wt %.
16. The CMP composition of claim 1 , wherein the complexing agent is present in the composition at a concentration in the range of about 10 to about 10,000 ppm.
17. The CMP composition of claim 1 further comprising potassium sulfate.
18. An aqueous chemical-mechanical polishing (CMP) composition for polishing germanium-antimony-tellurium (GST) alloys, the composition comprising an aqueous carrier containing, at point-of-use:
(a) about 0.01 to about 10 wt % of a particulate abrasive selected from the group consisting of a colloidal silica abrasive and ceria abrasive;
(b) about 10 to about 10,000 ppm of a water soluble surface active material;
(c) about 0.1 to about 2 wt % of an amino acid corrosion inhibitor; and
(d) about 10 to about 10,000 ppm of a complexing agent;
wherein the surface active material is selected based on the zeta potential of the particulate abrasive, such that when the abrasive has a positive zeta potential, the surface active material comprises a cationic material, and when the particulate abrasive has a negative zeta potential, the surface active material comprises an anionic material, a nonionic material, or a combination thereof.
19. The CMP composition of claim 18 wherein the particulate abrasive comprises ceria or an aminosilane surface-treated colloidal silica, and has a positive zeta potential, and the water soluble surface active material comprises a poly(methacryloyloxyethyl trimethylammonium)halide.
20. The CMP composition of claim 18 wherein the particulate abrasive comprises a colloidal silica having a negative zeta potential, and the water soluble surface active material comprises a poly(acrylic acid), a polyacrylamide, or a combination thereof.
21. The CMP composition of claim 20 further comprising potassium sulfate.
22. The CMP composition of claim 18 wherein the complexing agent comprises 1-hydroxyethylidene-1,1,-diphosphonic acid.
23. The CMP composition of claim 18 wherein the corrosion inhibitor comprises lysine.
24. A chemical-mechanical polishing (CMP) method for polishing germanium-antimony-tellurium (GST) alloy-containing substrate, the method comprising the steps of:
(a) contacting a surface of the substrate with a polishing pad and an aqueous CMP composition of claim 1 ; and
(b) causing relative motion between the polishing pad and the substrate while maintaining a portion of the CMP composition in contact with the surface between the pad and the substrate for a time period sufficient to abrade at least a portion of the germanium-antimony-tellurium alloy from the substrate.