Experimental and density functional theory study of complexing agents on cobalt dissolution in alkaline solutions

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.

Research of Vertical via Based on Silicon, Ceramic and Glass

With the increasing demand for high-density integration, low power consumption and high bandwidth, creating more sophisticated interconnection technologies is becoming increasingly crucial. Three-dimensional (3D) integration technology is known as the fourth-generation packaging technology beyond Moore's Law because of its advantages of low energy consumption, lightweight and high performance. Through-silicon via (TSV) is considered to be at the core of 3D integration because of its excellent electrical performance, lower power consumption, wider bandwidth, higher density, smaller overall size and lighter weight. Therefore, the particular emphasis of this review is the process flow of TSV technology. Among them, the research status of TSV hole etching, deep hole electroplating filling and chemical mechanical planarization (CMP) in TSV preparation process are introduced in detail. There are a multitude of inevitable defects in the process of TSV processing; thus, the stress problems and electrical characteristics that affect the reliability of TSV are summarized in this review. In addition, the process flow and process optimization status of through ceramic via (TCV) and through glass via (TGV) are discussed.

New insights into the aggregation and disaggregation between serpentine and pyrite in the xanthate flotation system

HYPOTHESIS

In xanthate flotation system, the aggregation of serpentine on sulfide minerals significantly weakened their floatability. And it was generally assumed that the electrostatic attraction was of the dominant driver for coating of serpentine slimes. In this paper, the hydrophobic interaction between the "talc-like" cleavage plane of serpentine and the xanthate-hydrophobized surface of sulfide minerals was proposed as the dominated driver.

EXPERIMENTS

To evaluate the aggregation of serpentine on pyrite surface, a novel experimental protocol was designed, and the aggregation behavior and mechanism in the absence and presence of sodium isobutyl xanthate (SIBX) were explored through in situ optical microscope, micro-flotation, contact angle, zeta potential and FT-IR. Afterwards, the disaggregation mechanism of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) to the aggregates of serpentine on pyrite surface was revealed.

FINDINGS

The electrostatic attraction facilitated the slight aggregation of serpentine slimes on bare pyrite surface. The hydrophobic interaction between the "talc-like" plane of serpentine and SIBX-covered pyrite significantly promoted the aggregation between them, which remarkably weakened the floatability of pyrite. The attendance of HEDP anions reversed the surface potential of the octahedral Mg-O layers of serpentine from the positive into the negative, thus to prevent the aggregation of the HEDP-anchored serpentine with the SIBX-covered pyrite via the strong electrostatic repulsion between them. As a result, the disaggregation as well as SIBX flotation separation of pyrite from serpentine was realized. This investigation also provided new insights into the aggregation and disaggregation between serpentine and sulfide minerals during froth flotation.

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.