Papers by Keyword: Cobalt

Abstract: The etching characteristics of ECD cobalt in different cleaning solutions were characterized using four-point probe, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy. 0.05% HF solution with saturated dissolved oxygen concentration was found to result in a substantial etch of ECD cobalt (~5 nm/min). In contrast, cleaning in the SC1 1:4:100 mixture and the formulated mixture led to a significantly lower etch amount, which could be explained by the formation of a passivation layer at the surface. XPS characterization indicated the formation of a cobalt hydroxide at the surface. The electrical evaluation of the DD structure carried out after cleaning using the formulated chemical mixture and subsequent metallization showed good yield for the 22 nm Kelvin vias, testifying an efficient cleaning of the Co surface at the via bottom.

Abstract: The introduction of Co into MOL and BEOL requires a robust wet clean, especially the optimization of the Co rinsing step seems to be critical. The wafer rinsing solutions with a precisely controlled pH and oxidizing additive have been developed to suppress the Co corrosion. In addition, the mechanism of passivation and corrosion of the cobalt surface as well as the passivation stability is discussed.

Abstract: The impact of dissolved oxygen (O₂) on cobalt (Co) corrosion in dilute HF (dHF) solution was studied. It was confirmed that Co etch rate was enhanced as the amount of dissolved O₂ in the HF solution increased. The Co etch rate was also found to increase radially outward when performed on a single-wafer spin process in atmospheric air due to the uptake of O₂ during the dispense process. The galvanic corrosion of Co was investigated with two types of structures with a Co/Cu interface in different dissolved O₂ concentrations, i.e. (1) Co bump structures on Cu and (2) Cu lines with a Co/TaN liner/barrier structure. By controlling both the dissolved and the atmospheric O₂ levels, galvanic corrosion prevention at the Co/Cu interface was achieved.

Abstract: This study focuses in the synthesis of ceramic pigments based on the crystal structure of willemite (Zn₂SiO₄). The willemite obtained from the combination of commercial zinc oxide and rice husk ash is produced in a conventional ceramic process without the use of mineralizer agent and with the addition of cobalt oxide or nickel oxide as the source of chromophore ions. The synthesis temperature used was 1200°C. The characterization of pigments involves the use of X-ray diffraction and scanning electron microscopy. The pigments applied in matte enamel and sintered at 1100°C or 1200°C developed color between blue and beige. The construction of absorbance curves showed the color development behavior of each pigment. The results showed the possibility of obtaining willemite, from rice husk ash and the color development efficiency of the material, besides showing the interference of chromophore ion (Ni and Co) in color development.

Abstract: The paper deals with the assessment of the effect of content of cobalt and cryogenic treatment on mechanical properties and structure of Vanadis 23 and Vanadis 30 PM high-speed steels. The studied characteristics are evaluated after conventional heat treatment (quenching and multiple tempering) and also when deep cryogenic treatment at -196°C/4 hours was inserted between quenching and tempering. The mechanical properties are assessed by a three-point bending flexural test and by measurement of the hardness. Metallographic analysis is performed using an energy dispersive spectrometer (EDS) and the scanning electron microscope (SEM).

Abstract: Zinc oxide nanoparticles doped with 0.2–1.5 mol% of Fe, Ni or Co and co-doped with 1 mol% of Ag were prepared by co-precipitation method and their photocatalytic activity in degradation of MB (methylene blue) water solution under ultraviolet irradiation was determined. X-ray diffraction analysis of the samples containing up to 0.5 mol% of iron group metals showed only ZnO and Ag phases. Crystallite size of doped ZnO nanoparticles was in the range of 27–31.6 nm depending on the sample composition and additional calcination at 400 °C. The photocatalytic activity of ZnO doped with iron group metals depended on the content of metals. The highest activity was observed for ZnO doped with 0.2 mol% of nickel. The co-doped with silver samples showed enhanced photocatalytic activity and higher reaction rate constant.

Abstract: The electrochemical behavior of cobalt in the presence of methylviologen (MV²⁺) dichloride was investigated in choline chloride-urea (1:2 molar ratio) deep eutectic solvent containing 1 mM CoSO₄ and 1 mM MV²⁺. Cyclic voltammetry of cobalt electrolyte after reduction process at stationary potential has shown the shift of oxidation peak to cathodic region with increase of reduction process time. The investigations carried out after electrolysis of the system containing 1 mM CoSO₄ and 1 mM MV²⁺ at the reduction peak of methylviologen dichloride have shown that there was an accumulation of cobalt reduced form in near-electrode region whereas the concentration of methylviologen reduced form has not changed. This may indicate that methylviologen dichloride is a mediator in electrochemical processes with respect to cobalt in the system under consideration.

Abstract: The formation of cobalt (Co) doped zinc oxide (ZnO) as photocatalyst for photodegradation of methyl orange dye was investigated. The ZnO photocatalyst was produced with different concentration of Co by using sol gel method. The hexagonal wurtzite and zincite structure were successfully formed through this method. The morphological observation of nanorod and nanodisk structure formed was done by Field Emission Scanning Electron Microscope (FESEM). While, the structural properties of Co doped ZnO were identified by X-ray Diffraction (XRD) and Raman spectroscopy. The degradation performance of methyl orange was assessed and performance of photocatalytic activity was correlated to the amount of dopant level and oxygen vacancy of photocatalyst. There is an optimum amount of Co that can be doped into ZnO nanostructure in order to provide better degradation of methyl orange.

Abstract: Bioremediation is the process of detoxification or elimination of pollutants using microorganisms with different metabolic capabilities. Biodegradation by natural populations of microorganisms is one of the primary mechanisms by which oil and other pollutants of hydrocarbon origin can be removed from the environment and it is also much cheaper than the other remediation technologies.In this study, we analyzed the samples of historical waste from the oil industry, which contained sand, organic materials, heavy fuel oil and catalysts used during the process of hydrodesulfurization (HDS) of oil. The aim was to examine the fate of cobalt and molybdenum, toxic heavy metals present in those catalysts. A consortium of microorganisms isolated from the complex pollutants from the oil industry was added to the samples. During the study, beside the transformation of cobalt and molybdenum forms, we also monitored the biodegradation process of the total petroleum hydrocarbons (TPH).

Abstract: Phage surface display technology is a useful tool for the identification of biosorptive peptides. In this work it is used for the identification of cobalt, nickel and gallium binding peptides. We present methods for the enrichment of metal ion binding bacteriophage clones from a commercial phage display library. Metal ion selective peptides are suitable to separate as well as concentrate cobalt and nickel from copper black shale leaching products (EcoMetals project) and gallium from industrial waste waters (EcoGaIn project). In contrast to common capture methods of specific binding phage for solid materials the ionic species have to be immobilized prior to the bio-panning procedure. This was realized by chemical complexation of the metal ions using commercial complexing agents on porous matrices. Moreover, an option to harvest non elutable strong binding phage is proposed.