Polishing compositions and methods for polishing cobalt films
The present disclosure relates to polishing compositions that can polish Cobalt (Co) films in semiconductor substrates containing a multitude of films including Co, metals, metal oxides and dielectrics. These polishing compositions comprise an abrasive, a weak acid acting as a removal rate enhancer (RRE), a pH adjuster, and an azole-containing corrosion inhibitor (CI). The RRE, pH adjuster and CI have a pKa in the 1-18 range (1 (pKa min )<pKa<18 (pKa max )). The pKa values of the individual components are related to the pH of the polishing composition/slurry (pH slurry ) by the following equation: pKa min +6<pH slurry <pKa max −6. The polishing composition also has less than about 100 parts per million (ppm) of sulfate ions and less than about 100 ppm of halide ions, and operates in the 7-12 pH range.
1. A polishing composition for polishing cobalt containing material, comprising:
a) an abrasive;
b) a weak acid removal rate enhancer;
c) an azole-containing corrosion inhibitor; and
d) a pH adjuster;
wherein said removal rate enhancer, said corrosion inhibitor, and said pH adjuster each have a pKa between 1 and 18, and
wherein the pH of the composition is between 7 and 12, and
wherein the composition has less than about 100 parts per million of sulfate ions and less than about 100 parts per million of halide ions, each based on the total weight of the composition.
2. The polishing composition of claim 1 , wherein said abrasive is selected from the group consisting of alumina, silica, titania, ceria, zirconia, co-formed products thereof, coated abrasives, surface modified abrasives, and mixtures thereof.
3. The polishing composition of claim 1 , wherein said removal rate enhancer is selected from the group consisting of gluconic acid, lactic acid, citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid, acetic acid, propionic acid, peracetic acid, succinic acid, lactic acid, potassium acetate, potassium citrate, amino acetic acid, phenoxyacetic acid, bicine, phosphoric acid, diglycolic acid, glyceric acid, tricine, alanine, histidine, valine, phenylalanine, proline, glutamine, aspartic acid, glutamic acid, arginine, lysine, tyrosine, benzoic acid, salts thereof, and mixtures thereof.
4. The polishing composition of claim 1 , wherein the azole-containing corrosion inhibitor is selected from the group consisting of triazole, tetrazole, benzotriazole, tolytriazole, aminotriazole, aminobenzimidazole, pyrazole, imidazole, aminotetrazole, and mixtures thereof.
5. The polishing composition of claim 1 , wherein the abrasive is present in an amount of about 0.05 to about 15 percent by weight, based on the total weight of the composition.
6. The polishing composition of claim 1 , wherein said removal rate enhancer is present in amount of about 0.1 to about 20 percent by weight, based on the total weight of the composition.
7. The polishing composition of claim 1 , wherein said corrosion inhibitor is present in an amount of about 0.05 to about 10 percent by weight, based on the total weight of the composition.
8. The polishing composition of claim 1 , wherein said pKa of said removal rate enhancer, said corrosion inhibitor, and said pH adjuster is between 2 and 10.
9. The polishing composition of claim 8 , wherein the composition has less than about 50 parts per million (ppm) of sulfate ions and less than about 50 ppm of halide ions.
10. The polishing composition of claim 1 , wherein the pH adjuster is a weak acid selected from the group consisting of citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, oxalic acid, acetic acid, propionic acid, peracetic acid, succinic acid, lactic acid, potassium acetate, potassium citrate, and combinations thereof.
11. The polishing composition of claim 1 , wherein the corrosion potential difference (ΔE corr ) between Cu and Co in potentiodynamic Tafel plots is less than 30 mV (ΔE corr <30 mV).
12. A point of use polishing slurry comprising
a) an abrasive;
b) a weak acid removal rate enhancer;
c) an azole-containing corrosion inhibitor; and
d) a pH adjuster;
wherein said removal rate enhancer, said corrosion inhibitor, and said pH adjuster each have a pKa between 1 and 18, and
wherein the pH of the composition is between 7 and 12, and
wherein the composition has less than about 100 parts per million of sulfate ions and less than about 100 parts per million of halide ions, each based on the total weight of the composition,
wherein an oxidizer is added to the polishing composition of claim 1 at the point of use, and
wherein said abrasive if selected from the group consisting of silica, titania, ceria, zirconia, co-formed products thereof, coated abrasives, surface modified abrasives, and mixtures thereof.
13. The polishing slurry of claim 12 , wherein said oxidizer is hydrogen peroxide, ammonium persulfate, or a combination thereof.
14. The polishing slurry of claim 12 , wherein said oxidizer is present in the point of use polishing slurry in an amount of about 0.0001 wt % to about 5 wt %, based on the total weight of the polishing slurry.