Method to increase barrier film removal rate in bulk tungsten slurry
The invention relates to a chemical-mechanical polishing composition comprising (a) a first abrasive comprising cationically modified colloidal silica particles, (b) a second abrasive having a Mohs hardness of about 5.5 or more, (c) a cationic polymer, (d) an iron containing activator, (e) an oxidizing agent, and (f) water. The invention also relates to a method of chemically mechanically polishing a substrate, especially a substrate comprising tungsten and barrier layers (e.g., nitrides), with the polishing composition.
1. A chemical-mechanical polishing composition comprising:
(a) a first abrasive comprising cationically modified colloidal silica particles,
(b) a second abrasive having a Mohs hardness of about 5.5 or more, wherein the second abrasive is selected from α-alumina particles, zirconia particles, diamond particles, and combinations thereof,
(c) a cationic polymer,
(d) an iron containing activator,
(e) an oxidizing agent, and
(f) water.
2. The polishing composition of claim 1 , wherein the cationically modified colloidal silica particles have a zeta potential of greater than about 20 mV at a pH of about 2.5.
3. The polishing composition of claim 1 , wherein the cationically modified colloidal silica particles have an average particle size of about 50 nm to about 200 nm.
4. The polishing composition of claim 1 , wherein the cationically modified colloidal silica particles are present in the polishing composition in an amount of about 0.01 wt. % to about 5 wt. %.
5. The polishing composition of claim 1 , wherein the second abrasive comprises α-alumina particles.
6. The polishing composition of claim 1 , wherein the second abrasive is present in the polishing composition in an amount of about 25 ppm or higher.
7. The polishing composition of claim 6 , wherein the second abrasive is present in the polishing composition in an amount of about 50 ppm to about 500 ppm.
8. The polishing composition of claim 1 , wherein the cationic polymer has a molecular weight of about 100,000 g/mol or less.
9. The polishing composition of claim 8 , wherein the cationic polymer has a molecular weight of about 2,000 g/mol to about 15.000 g/mol.
10. The polishing composition of claim 1 , wherein the cationic polymer is polydiallyldimethylammonium chloride (pDADMAC).
11. The polishing composition of claim 1 , wherein the cationic polymer is present in the polishing composition in an amount of about 1 to about 100 ppm.
12. The polishing composition of claim 1 , wherein the iron containing activator comprises a soluble iron salt.
13. The polishing composition of claim 12 , wherein the soluble iron sa is ferric nitrate.
14. The polishing composition of claim 1 , wherein iron from the iron containing activator is present in the polishing composition in an amount of about 1 ppm to about 100 ppm.
15. The polishing composition of claim 12 , further comprising a stabilizer bound to the soluble iron salt, wherein the stabilizer is selected from phosphoric acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, and combinations thereof.
16. The polishing composition of claim 15 , wherein the stabilizer is present in the polishing composition in an amount of about 20 ppm to about 2,000 ppm.
17. The polishing composition of claim 1 , wherein the oxidizing agent is hydrogen peroxide.
18. The polishing composition of claim 1 , wherein the polishing composition has a pH of about 2 to about 4.
19. A method of chemically mechanically polishing a substrate comprising:
(i) providing a substrate,
(ii) providing a polishing pad,
(iii) providing a chemical-mechanical polishing composition comprising:
(a) a first abrasive comprising cationically modified colloidal silica particles,
(b) a second abrasive having a Mohs hardness of about 5.5 or more,
(c) a cationic polymer,
(d) an iron containing activator,
(e) an oxidizing agent, and
(f) water,
(iv) contacting the substrate with the polishing pad and the chemical-mechanical polishing composition, and
(v) moving the polishing pad and the chemical mechanical polishing composition relative to the substrate to abrade at least a portion of the substrate to polish the substrate, wherein the substrate comprises both a tungsten layer and a titanium nitride layer on a surface of the substrate, and wherein both the tungsten layer and the titanium nitride layer are abraded to polish the substrate.
20. The method of claim 19 , wherein the canonically modified colloidal silica particles have a zeta potential of greater than about 20 mV at a pH of about 2.5.
21. The method of claim 19 , wherein the canonically modified colloidal silica particles are present in the polishing composition in an amount of about 0.05 wt. % to about 5 wt. %.
22. The method of claim 19 , wherein the second abrasive is selected from α-alumina particles, zirconium particles, diamond particles, and combinations thereof.
23. The method of claim 19 , wherein the second abrasive comprises α-alumina particles.
24. The method of claim 19 , wherein the second abrasive is present in the polishing composition in an amount of about 25 ppm or higher.
25. The method of claim 19 , wherein the cationic polymer has a molecular weight of about 100,000 g/mol or less.
26. The method of claim 25 , wherein the cationic polymer is polydiallyldimethylammonium chloride (pDADMAC).
27. The method of claim 19 , wherein iron from the iron-containing activator is present in the polishing composition in an amount of about 1 ppm to about 100 ppm.
28. The method of claim 19 , wherein the polishing composition has a pH of about 2 to about 4.