Passivation Of Copper Research Articles

Investigation of the impact of environmental conditions on the mechanical properties of thin-film copper wafers

Thin-film copper offers excellent film texture for multilevel interconnections in integrated circuit fabrication due to its superior resistance to electromigration and high electrical conductivity. To perform a chemical mechanical planarization process during semiconductor fabrication of copper, it is necessary to have a thorough understanding of the nanomechanical properties of thin-film copper. In this study, thin-film copper and reacted passivation layers on silicon substrate wafers are investigated for their nanomechanical properties under various environmental conditions. The results of this study indicate that thin-film copper passivation layers have different properties in deionized (DI) water and polishing slurry environments compared to thin-film copper exposed to ambient air. Interestingly, variations in temperature within wet environments do not significantly affect the properties of thin-film copper wafers; but changes in properties are largely driven by chemical processes. The insights gained from this study emphasize the significance of considering both the passivation layers and wet environments in semiconductor fabrication processes, which contributes to the advancement of copper-based interconnect materials and optimization of the chemical mechanical planarization process in semiconductor manufacturing.

Electrochemical oxidation of brass in electrolytes with different viscosities

The effect of the glycerol addition to 1 M NaOH aqueous electrolyte used for the passivation of copper on the morphology, crystalline structure as well as composition was explored for the first time. It was revealed that the morphology of the obtained material depends strongly on the content of the glycerol in the electrolyte, the duration of the passivation, and to a lesser extent on the applied potential in the studied range. Moreover, even a small addition (5 vol.%) of glycerol changed significantly the composition of the obtained passive layer. In the absence of glycerol, barrel-like structures composed mostly of crystalline Cu(OH)2 were observed. After the addition of glycerol, the formation of the passive layer with spiked petals, composed mainly of crystalline ZnO and amorphous Cu2O, was detected. Moreover, the used potential had an influence on the macroscopic behavior of the samples – for samples prepared at 100 mV vs. Hg|HgO – poor adhesion to the substrate surface after sample drying was noted. Significantly improved macroscopic stability of passive layers obtained at the applied potential of 300 mV was observed. Such samples, prepared at selected glycerol concentrations were used for electrochemical carbon oxide reduction reaction studies to explore one possible application of the presented material.

Pharmaceutical active compounds in sewage sludge: Degradation improvement and conversion into an organic amendment by bioaugmentation-composting processes

Around 143,000 chemicals find their fate in wastewater treatment plants in the European Union. Low efficiency on their removal at lab-based studies and even poorer performance at large scale experiments have been reported. Here, a coupled biological technology (bioaugmentation and composting) is proposed and proved for pharmaceutical active compounds degradation and toxicity reduction. The optimization was conducted through in situ inoculation of Penicillium oxalicum XD 3.1 and an enriched consortium (obtained from non-digested sewage sludge), into pilot scale piles of sewage sludge under real conditions. This bioaugmentation-composting system allowed a better performance of micropollutants degradation (21 % from the total pharmaceuticals detected at the beginning of the experiment) than a traditional composting process. Particularly, inoculation with P. oxalicum allowed the degradation of some recalcitrant compounds like carbamazepine, cotinine and methadone, and also produced better stabilization features in the mature compost (significant passivation of copper and zinc, higher macronutrients value, adequate physicochemical conditions for soil direct application and less toxic effect on germination) compared to the control and the enriched culture. These findings provide a feasible, alternative strategy to obtain a safer mature compost and a better removal of micropollutants performance at large scale.

Recent progress on bumpless Cu/SiO2 hybrid bonding for 3D heterogeneous integration

PurposeBumpless Cu/SiO2 hybrid bonding, which this paper aims to, is a key technology of three-dimensional (3D) high-density integration to promote the integrated circuits industry’s continuous development, which achieves the stacks of chips vertically connected via through-silicon via. Surface-activated bonding (SAB) and thermal-compression bonding (TCB) are used, but both have some shortcomings. The SAB method is overdemanding in the bonding environment, and the TCB method requires a high temperature to remove copper oxide from surfaces, which increases the thermal budget and grossly damages the fine-pitch device.Design/methodology/approachIn this review, methods to prevent and remove copper oxidation in the whole bonding process for a lower bonding temperature, such as wet treatment, plasma surface activation, nanotwinned copper and the metal passivation layer, are investigated.FindingsThe cooperative bonding method combining wet treatment and plasma activation shows outstanding technological superiority without the high cost and additional necessity of copper passivation in manufacture. Cu/SiO2 hybrid bonding has great potential to effectively enhance the integration density in future 3D packaging for artificial intelligence, the internet of things and other high-density chips.Originality/valueTo achieve heterogeneous bonding at a lower temperature, the SAB method, chemical treatment and the plasma-assisted bonding method (based on TCB) are used, and surface-enhanced measurements such as nanotwinned copper and the metal passivation layer are also applied to prevent surface copper oxide.

Communication—Exploration of Plasma Oxidized Copper Oxide as a Copper Passivation Layer

Passivation properties of the plasma oxidized copper oxide on the copper line have been studied using the electromigration stress method. The self-aligned copper oxide passivation layer has the unique property of gettering copper atoms diffused through it at the high temperature raised from the stress current induced Joule heating. On the other hand, the line broken time is shortened with the increase of the copper oxide passivation layer thickness. Therefore, for the passivation application, a thin copper oxide layer is better than a thick copper oxide layer.

Studying the Effect of Butanol on the Anode Behavior of Copper in Phosphoric Acid Solutions

The anode behavior of the copper electrode immersed in butanol phosphate electrolytes has been studied. The polarization dependences of the electrode allowed us to detect the sections that correspond to the passive and active states of copper and we also established the zone of the combined behavior of the processes of the copper dissolution and oxygen release. It was also established that a butyl alcohol contributes to an abrupt decrease in current densities in the entire region of anode potentials. The addition of butanol conditions the disappearance of current oscillations that can be seen on polarization dependences in phosphate solutions. Evidently, a decrease in the current densities is a consequence of the butanol adsorption on the copper surface and its participation in the formation of passive films. The specific features of the copper passivation in butanol phosphate electrolytes are characterized by the appearance of the explicit current peak that separates active and passive state zones at the ratio of C4H9OН:H3PO4 =1:3.As the alcohol-to-acid ratio increases, the peak gradually decreases. The addition of butanol has no determining influence on the potential value that corresponds to the started oxygen release. Currentefficiency values for the copper dissolution depend on the anode current density ja and the electrolyte composition. An increase in ja results in a decreased current efficiency value. An increase in the С4Н9ОН content has a similar action. Maximum current efficiency values are observed at ja=0.5–2 А∙dm-2, and they correspond to the active copper state. The dependences obtained for the copper dissolution rate allowed us to establish that υрalso increases with an increase in the current density up to ja=20 А∙dm-2. The copper treatment quality depends on the current density and the electrolyte composition. The solutions with the ratio of C4H9OН:H3PO4=2:1fail to provide a high quality treatment; the surface is not glossy and it has grinding traces. A high-quality treatment is observed in the electrolytes with the ratio of C4H9OН:H3PO4 =1:2 and lower. The electrochemical polishing in such solutions results in the glossy copper surface with the smoothed relief and it has no polishing traces.

Ferrihydrite reduces the bioavailability of copper and cadmium and phosphorus release risk in hydroxyapatite amended soil

Hydroxyapatite (HAP) can effectively decrease bioavailability of trace metals in soils, but the phosphorus (P) release risk was not fully known. In this study, the impacts of ferrihydrite (FH) on passivation of copper (Cu) and cadmium (Cd) and P release risk in soil amended by HAP were investigated under flooding conditions. Results showed that the combinations of HAP and FH increased soil pore water pH by 0.74–2.24 units and reduced phosphate by 71.1–99.5% than single HAP. Soil pore water Cu2+ and Cd2+ in HAP plus 5% FH treated soils were decreased by 96.8–98.6% and 86.6–98.6% than those of single HAP. The combinations of HAP and FH significantly decreased CaCl2 extractable Cu and Cd by 55.9–99% and 13–72.2%, respectively. Moreover, the combinations of HAP and FH significantly decreased exchangeable Cu 47.1–91.5%, but only FH5 decreased exchangeable Cd by 69.4% than the single HAP. Amorphous iron oxide in FH treated soils was 4.06–20 times higher than control, but some of them were transformed into crystalline iron oxide after 42-d flooding incubation. The FH significantly decreased soil labile P by 42.8–78.8% in the presence of HAP and increased stable P by 23.1–33.5% than the single HAP. This study suggested that the addition of FH can not only promote the passivation of HAP on Cu and Cd in the soil, but also reduce the P release risk. Overall, this study highlighted the potential value of the combination of HAP and FH in the passivation of Cu and Cd contaminated soils.

Environment-friendly and chromium-free passivation of copper and its alloys

Benzotriazole (BTA) and tolyltriazole (TTA) were used to passivate pure copper and chromium bronze alloys for environmental protection. Using the chemical immersion treatment, a dense film of chromium-free passivation layer was formed on surfaces of both the pure copper and chromium bronze alloys. Microstructure, crystalline phases and chemical bonds of the passivation layers were systematically characterized, and the passivation mechanisms were studied. The passivation layer was mainly consisted of CuO, Cu2O, polymers of Cu-BTA-TTA and Cu(I)BTA-TTA. The formation mechanism of the chromium-free passivation layer was identified as combined oxidation and adsorption, and the main passivation processes included oxidation and dissolution of the matrix, adsorption of BTA and its derivatives, self-stabilization process of the adsorbed film, and filling of passivation film’s voids by oxide particles.

Streamlined copper defenses make Bordetella pertussis reliant on custom-made operon

Copper is both essential and toxic to living beings, which tightly controls its intracellular concentration. At the host–pathogen interface, copper is used by phagocytic cells to kill invading microorganisms. We investigated copper homeostasis in Bordetella pertussis, which lives in the human respiratory mucosa and has no environmental reservoir. B. pertussis has considerably streamlined copper homeostasis mechanisms relative to other Gram-negative bacteria. Its single remaining defense line consists of a metallochaperone diverted for copper passivation, CopZ, and two peroxide detoxification enzymes, PrxGrx and GorB, which together fight stresses encountered in phagocytic cells. Those proteins are encoded by an original, composite operon assembled in an environmental ancestor, which is under sensitive control by copper. This system appears to contribute to persistent infection in the nasal cavity of B. pertussis-infected mice. Combining responses to co-occurring stresses in a tailored operon reveals a strategy adopted by a host-restricted pathogen to optimize survival at minimal energy expenditure.

Sustained Effects of Remediation Materials on Soil Copper Remediation Under Oil-Rice Rotation

In this study, a continuous rape-rice rotation plot experiment was conducted over three years. Repair materials were continuously applied in the first two years, and no repair materials were applied in the second year. The repair effects of hydroxyapatite, lime, biochar, bio-organic fertilizer, and nano-materials on copper contaminated soil and the enrichment of copper in different parts of rape and rice were investigated. The results show that hydroxyapatite, lime, and nanomaterials can significantly increase soil pH, and different restoration materials can effectively inhibit the movement of soil copper. The effective copper treatment with lime restoration soil had the largest decrease. The four seasons of continuous application of restoration materials were 38.9%, 34.9%, 27.88%, and 29.04%, respectively, and the subsequent effect of lime passivation of effective copper was better than other restoration materials. The application of the repair material significantly reduced the copper content in edible parts of rape and rice. In the four seasons of application of the repair material, the maximum copper content in edible parts of different crops decreased by 46.03%, 22.2%, 29.44%, and 31.71%, respectively. Due to the application effect of the repair material, the copper content in the edible part of the two season crops, without the repair material, did not exceed the national food safety limit. With the use of different repair materials, the yields of rapeseed and rice were improved. This test can provide some theoretical basis and technical support for soil improvement in copper-contaminated areas.

Electrochemical corrosion behavior and surface passivation of bulk nanocrystalline copper in alkaline solution

PurposeThis paper aims to focus on an assessment of the electrochemical corrosion performance of bulk NC copper in a variety of corrosion environments.Design/methodology/approachThe electrochemical corrosion behavior of bulk nanocrystalline (NC) copper prepared by inert gas condensation andin situwarm compress technique was studied by using potentiodynamic polarization and electrochemical impedance spectroscopy tests in de-aerated 0.1 M NaOH solution.FindingsNC copper exhibited a typical active-passive-transpassive behavior with the formation of duplex passive films, which was qualitatively similar to coarse-grain (CG) copper. Although a compact passive film formed on NC copper surface, the corrosion resistance of NC copper was lower in comparison with CG copper. The increase in corrosion rate for NC copper was mainly attributed to the high activity of surface atoms and intergranular atoms. These atoms led to an enhancement of passive ability and an increase of dissolution rate of passive film in oxygen-deficiency solution. For NC copper, the corrosion resistance decreased as grain size increased in NC range.Originality/valueThe difference in corrosion resistance between bulk NC copper and its CG counterpart is dependent upon the corrosion solution. In a previous work, the potentiodynamic polarization tests revealed that NC copper bulks (grain size 48, 68, 92 nm) had identical corrosion resistance to CG copper bulk in naturally aerated 0.1 M NaOH solution. The results might be related to the dissolved oxygen in the medium.

In Situ X-ray Diffraction and Spectro-Microscopic Study of ALD Protected Copper Films.

In many applications of copper in industry and research, copper migration and degradation of metallic copper to its oxides is a common problem. There are numerous ways to overcome this degradation with varying success. Atomic layer deposition (ALD) based encapsulation and passivation of the metallic copper recently emerged as a serious route to success owing to the conformality and density of the ALD films. So far, the majority of the studies have been focused on corrosion protection of copper in a variety of chemical environments, mostly at ambient temperature. An investigation of the stability of the ALD film stacks and copper's interaction with them at elevated temperatures has been lacking. Here, we study the mitigation of copper oxidation and migration in 50 nm thick Al2O3/TiO2 and Al2O3/SiO2 bilayer ALD stacks. First, the corrosion dynamics were investigated via in situ X-ray diffraction (XRD) at 350 °C under atmospheric conditions, and second, the interaction of copper with the passivation layers have been examined post factum using detailed spectro-microscopic investigations. According to the XRD results, both ALD films exhibited excellent oxidation protection. In contrast, bare Cu immediately started to oxidize at 350 °C and transformed entirely to its known oxide phases in 4 h. Spectro-microscopic studies revealed that there are structural and chemical changes on the top surface and within the film stacks. The TiO2 layer was crystallized during annealing, while the SiO2 layer stayed in the amorphous phase, which was analyzed by grazing incidence XRD and transmission electron microscopy. According to scanning electron microscopy and X-ray photoelectron spectroscopy analysis, copper was detected on the surface with a higher amount in Al2O3/TiO2 than Al2O3/SiO2, 5.2 at.% and 0.7 at.%, respectively. Based on the surface and cross-sectional analysis, copper migration was observed on both layers, albeit more substantially in Al2O3/TiO2. In the case of Al2O3/SiO2, the bulk of the copper was captured at the interface of the two oxides.

Area-Selective Deposition by a Combination of Organic Film Passivation and Atomic Layer Deposition

To enable the downscaling of Integrated Circuit (IC) components accordingly to Moore’s law, novel nano-patterning techniques and materials are essential. Self-Aligned patterning schemes, such as Area Selective Deposition (ASD), are receiving increasing attention due to challenges created by the continuous shrinking of critical dimensions (e.g. self-aligned vias to lines in multi-level interconnect architectures). In ASD, a given film is deposited exclusively on the desired growth area with respect to the non-growth area. Typically, this can be achieved by exploiting material properties, such as surface chemical composition variations, in combination with surface-sensitive deposition techniques, such as Atomic Layer Deposition (ALD). In addition, the ALD self-limiting half-cycle surface reactions provide a layer-by-layer growth mechanism, which is strongly dependent upon the chemical reactivity to the underlying layer. Intrinsic growth nucleation variations on different surfaces can be exploited in an ASD scheme, but this effect is typically limited to very few ALD cycles. In this talk, Self-Assembled Monolayers (SAMs) are evaluated as a passivation coating to extend the ASD process window. Potential applications that will be discussed are Copper passivation in a self-aligned via patterning process flow and area-selective bottom-up VIA fill in an interconnect metallization scheme.

Fabrication and characterization of oxide nano-needles formed by copper passivation in sodium hydroxide solution

Electropolished copper foil was passivated in aqueous solution of 1.0 M NaOH at negative potential range vs. silver chloride electrode at room temperature. The passivations were performed at −50, −100, −150, and −200 mV for 1, 5 or 15 h. The resulting nano-needle layers were characterized by X-ray photoelectron spectroscopy and band gaps derived from UV–Vis spectroscopy evidencing coincidence of Cu(OH)2, CuO and Cu2O phases. Scanning Electron Microscopy revealed that the diameter of nanoneedles was not influenced by the passivation potential, however, the nanoneedles diameter was decreasing with extension of the passivation time (the smallest diameter obtained was 60 ± 17 nm). Additionally, the as-prepared oxide nano-needles were found to be polycrystalline, without any post treatments. All together, chemical compositionand physical properties (band gap) show that the inner part of the grown nano-needles is rather made of Cu2O, while outer part, there where the passivation reaction takes place, is made of CuO and Cu(OH)2.

Adsorption of 5-alkyl-3-amino-1,2,4-triazoles from aqueous solutions and protection of copper from atmospheric corrosion

Adsorption of 5-alkyl derivatives of 3-amino-1,2,4-triazole and their effect on the passivation of copper have been studied in neutral buffer solution using polarization, ellipsometric and XPS techniques. Triazoles are capable of forming passive layers on the copper surface at very low concentration. The adsorption of 3-amino-1,2,4-triazole derivatives is described by the Temkin equation and the values of free adsorption energies increase with increasing of the length of alkyl. The layers formed by 5-alkyl-3-amino-1,2,4-triazoles provide protection of copper under the impact of salt spray. The mixtures of 3-amino-1,2,4-triazole derivatives can show the higher performance than each of the single component.

Effect of additives on anode passivation in direct electrolysis process of copper—nickel based alloy scraps

Effects of nickel component, thiourea, glue and chloride ions and their interactions on the passivation of copper—nickel based alloy scrap anodes were investigated by combining conventional electrochemical techniques. Results obtained from chronopotentiometry and linear voltammetry curves showed that the Ni component made electrochemical stability of the anode strong and difficult to be corroded, caused by the adsorption of generated Cu2O, NiO or copper powder to the anode surface. The Ni2+ reducing Cu2+ to Cu+ or copper powder aggravated the anode passivation. In a certain range of the glue concentration ≤8×10-6 or thiourea concentration ≤4×10-6, the increase of glue or thiourea concentration increases the anode passivation time. Over this range, glue and thiourea played an adverse effect. The increase of chloride ions concentration led to the increase in passivation time.

Substituted benzotriazoles as inhibitors of copper corrosion in borate buffer solutions

The adsorption of substituted 1,2,3-benzotriazoles (R-BTAs) onto copper is measured via ellipsometry in a pure borate buffer (pH 7.4) and satisfactorily described by Temkin’s isotherm. The adsorption free energy (−ΔG a 0 ) values of these azoles are determined. The (−ΔG a 0 ) values are found to rise as their hydrophobicity, characterized by the logarithm of the partition coefficient of a substituted BTA in a model octanol–water system (logP), grows. The minimum concentration sufficient for the spontaneous passivation of copper (C min) and a shift in the potential of local copper depassivation with chlorides (E pt) after an azole is added to the solution (i.e., ΔE = E pt in − E pt backgr characterizing the ability of its adsorption to stabilize passivation) are determined in the same solution containing a corrosion additive (0.01М NaCl) for each azole under study. Both criteria of the passivating properties of azoles (logC min and ΔE) are shown to correlate linearly with logP, testifying to the role played by surface activity of this family of organic inhibitors in protecting copper in an aqueous solution.

Flower-like architecture of CoSn4 nano structure as anode in lithium ion batteries

CoSn4 nano-particles were synthesized on Cu and Ni substrates through pulsed current electrodeposition and used as anode in lithium ion batteries. Nano particles with Flower-like morphology were obtained through applying an average current density of 85 mA/cm2 on Ni substrate while the particles formed using constant current electrodeposition are greater in size ca. 500 nm. Optimum discharge capacity of synthesized CoSn4 was obtained 848 mAh g−1 which reduced to 500 mAh g−1 at 120th cycle indicating an enhanced electrochemical performance compared to anode films synthesized through other pulsed current densities and also constant current electrodeposition. This high discharge capacity and cycleability is attributed to finer crystal grains and flower-like morphology of nano particles. Also, the sample synthesized on Ni substrate showed higher cycleability and noticeably lower resistance. High resistance of anode film synthesized on Cu substrate is due to the corrosion and passivation of copper occurred by HF formation in LiPF6 electrolyte.

Morphology and photoluminescence of nanostructured oxides grown by copper passivation in aqueous potassium hydroxide solution

Copper foil was anodized in 1M KOH at potentials ranging from −400 to −100mV vs. Ag|AgCl electrode. Cyclic voltammetry showed a distinct peak with a maximum at around −150mV. For anodizing at −100 and −200mV, nanowires with diameters of ca. 19 and 24nm respectively were found to be grown. Moreover, photoluminescence and X-ray diffraction show that the dominant phase is the CuO phase. At lower potentials, cuboidal micron sized crystals were formed and Cu2O was found to be the major phase.

Sodium Passivation of the Grain Boundaries in CuInSe2 and Cu2ZnSnS4 for High‐Efficiency Solar Cells

It is well known that sodium at grain boundaries (GBs) increases the photovoltaic efficiencies of CuInSe2 and Cu2ZnSnS4 significantly. However, the mechanism of how sodium influences the GBs is still unknown. Based on the recently proposed self‐passivation rule, it is found that the dangling bonds in the GBs can completely be saturated through doping the Na, thus GB states are successfully passivated. It is shown that the Na can easily incorporate into the GB with very low formation energy. Although Cu can also passivate the GB states, it requires a copper rich condition which, however, suppresses the formation of copper vacancies in the bulk and thus decreases the concentration of hole carriers, so copper passivation is practically not as beneficial as sodium. The present work reveals the mechanism about how the Na enhances the photovoltaic performance through passivating the dangling bonds in the GBs of chalcogenide semiconductors, and sheds light on how to passivate dangling bonds in GBs with alterative processes.