Triple Synergism Effect of Ammonium Nitrilotriacetate on the Chemical Mechanical Polishing Performance of Ruthenium Barrier Layers

Abstract

As the feature size of integrated circuits continues to decrease, ruthenium (Ru) has been suggested as the successor to traditional Ta/TaN bilayers for barrier layer materials due to its unique properties. This research delves into the effects of ammonium nitrilotriacetate (NTA(NH₄)₃) on the chemical mechanical polishing (CMP) performance of Ru in H₂O₂-based slurry. The removal rate (RR) of Ru surged from 47 to 890 Å min^-1, marking an increase of about 17 times. The essence of this mechanism lies in the triple synergistic effects of NTA(NH₄)₃ in promoting ruthenium (Ru) removal: 1) The interaction between ${\mathrm{NH}}_4^{+}$ from NTA(NH₄)₃ and SiO₂ abrasives; 2) The chelating action of [(NH₄)N(CH₂COO)₃]^2- from NTA(NH₄)₃ on Ru and its oxides; 3) The ammoniation and chelation of Ru and its oxides by ${\mathrm{NH}}_4^{+}$ from NTA(NH₄)₃, which enhance the dissolution and corrosion of oxidized Ru, making its removal during the barrier layer CMP process more efficient through mechanical means. This research introduces a synergistic approach for the effective removal of Ru, shedding light on potential applications of CMP in the field of the integrated circuits.

Keywords: ammonium nitrilotriacetate; barrier layer; chelating agent; chemical mechanical polishing; triple synergistic effects.