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

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 angstrom 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 NH4+${\mathrm{NH}}_{\mathrm{4}}<^>{\mathrm{ + }}$ 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 NH4+${\mathrm{NH}}_{\mathrm{4}}<^>{\mathrm{ + }}$ 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. The core mechanism of NTA(NH4)3 in promoting ruthenium (Ru) removal involves a triple synergistic effect: 1) interaction of NH4+${\rm{NH}}_{{4}}<^>{{ + }}$ in NTA(NH4)3 with silica abrasives; 2) chelation effect of [(NH4)N(CH2COO)3]2- in NTA(NH4)3 on Ru and its oxides; 3) ammoniation and chelation effect of NH4+${\mathrm{NH}}_{\mathrm{4}}<^>{\mathrm{ + }}$ in NTA(NH4)3 on Ru and its oxides. This triple synergistic removal mechanism simultaneously achieves a high removal rate and low surface defects, providing a new perspective in the field of barrier layer CMP.image