Exploring combined effect of nitrilotriacetic acid and inhibitor on copper surface in alkaline solution: Insights from experiments and molecular dynamics simulation studies

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 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 betweenNH 4 + ${\mathrm{NH}}_{\mathrm{4}}^{\mathrm{+}}$ 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 byNH 4 + ${\mathrm{NH}}_{\mathrm{4}}^{\mathrm{+}}$ 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.

Experimental and Computational Studies on Octyl Hydroxamic Acid as an Environmentally Friendly Inhibitor of Cobalt Chemical Mechanical Polishing

Octyl hydroxamic acid (OHA) was investigated as an inhibitor in H₂O₂-based alkaline silica dispersions for the polishing of cobalt (Co) films for interconnect applications. A combination of experiments and density functional theory (DFT) was used to investigate the inhibition effect and the mechanism of OHA on the Co surface. On the basis of the experiments, it can be proven that OHA has an inhibition effect on Co, which came from the inhibition of the cathodic reaction. The X-ray photoelectron spectroscopy (XPS) experiments show that the adsorption of OHA weakened the oxidation of the Co surface and protected the Co surface from corrosion. On the basis of the calculations, it can be proven that the OHA^ketone (ion) is most likely to react with the Co surface, and it can adsorb on the Co surface by Co-O bonds. This study provides important microscopic insights for understanding the corrosion protection of Co interconnect metals and helps to explain the corrosion inhibition mechanism of the organic-metal interface during the CMP process.

Effect of ethylenediamine on CMP performance of ruthenium in H2O2-based slurries

With the aggressive scaling of integrated circuits, ruthenium has been proposed as the next generation barrier material to replace the conventional bilayer of tantalum and tantalum nitride due to its properties such as allowing direct copper electrodeposition. In this work, the effect of ethylenediamine (EDA) on the chemical mechanical polishing (CMP) properties of ruthenium in H₂O₂-based slurries was investigated. The results show that EDA or H₂O₂ alone has little effect, but the combined use of EDA and H₂O₂ significantly enhances the removal rate of ruthenium. Subsequently, the mechanism of action of ruthenium removal promoted by EDA was studied by combining CMP experiments, electrochemical experiments and surface chemical characterization methods. It is indicated that EDA molecules react with ruthenium oxide (not ruthenium metal) to generate a large number of complexes, which promotes the dissolution of ruthenium oxides and the corrosion of ruthenium. More importantly, the oxide layers on the ruthenium surface become rough and porous, and can be easily removed by mechanical action during the ruthenium CMP process. Meanwhile, the use of EDA can reduce the electrostatic repulsive force between the SiO₂ particles and ruthenium surface in the CMP process, thus further accelerating the ruthenium removal. In order to obtain an adequate removal rate selectivity of ruthenium versus copper, the corrosion inhibitors for copper were added. As a consequence, the removal rate selectivity of 1.13 : 1 was obtained, while also reducing the corrosion potential difference between ruthenium and copper to 17 mV.

In the ruthenium CMP process, the removal rate of ruthenium can be effectively improved by adding EDA and H₂O₂ into SiO₂-based slurries.