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The properties of Cu(V) alloy films were investigated to evaluate its potential use as self-forming diffusion barrier in copper metallization. Cu(V) alloy films were deposited on SiO 2 /Si substrates by magnetron sputtering. Cu(V)/SiO 2 /Si systems were subsequently annealed at various temperatures and analyzed by four-point probe measurement (FPP), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). After annealed at 500 °C, the resistivity of the Cu(V) films reduced to 3.1 μΩ cm, there is no obvious increase in resistivity. XRD suggest that Cu alloy film has preferential (111) crystal orientation and no extra peak corresponding to Cu and Si even after annealed at 500 °C. According to TEM results, a self-formed thin layer with the thickness of about 8 nm is observed at the interface between Cu alloy and the SiO 2 /Si substrate in the sample annealed at400 °C. As XPS results, after annealed at 400 °C and 500 °C, V atoms are observed at the surface of the Cu(V) films and the interface of the Cu(V) and SiO 2 /Si. The formation of the self-formed thin layer is probably due to the separation of V at the interface. The sharp declines of the Cu and Si concentrations at the interface indicate a lack of inter-diffusion between Cu and SiO 2 /Si. Adding small amounts of V to Cu film can improve the barrier performance and thermal stability compared with pure Cu contact systems. [ABSTRACT FROM AUTHOR]

Abstract: The properties of Cu–Zr and Cu–Ru alloy films were comparatively studied to evaluate their potential use as alloying elements. Cu alloy films were deposited on SiO2/Si substrates by magnetron sputtering. Samples were subsequently annealed and analyzed by four-point probe measurement, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and Auger electron spectroscopy. X-ray diffraction data suggest that Cu film has preferential (111) crystal orientation and no extra peak corresponding to any compound of Cu, Zr, Ru, and Si. According to transmission electron microscopy results, Cu grains grow in size for both systems but the grain sizes of the Cu alloy films are smaller than that of pure Cu films. These results indicate that Cu–Zr film is suitable for advanced barrier-free metallization in terms of interfacial stability and lower resistivity. [Copyright &y& Elsevier]

Abstract: Zr–Ti–N film prepared by sputtering deposition has been employed as a potential diffusion barrier for Cu metallization. It is thought that the existing states of Ti and Zr in the films are Ti–N and Zr–N phase in Zr–Ti–N films. Material analysis by XRD, XPS and sheet resistance measurement reveal that the failure of Zr–N film is mainly due to the formation of Cu3Si precipitates at the Zr–N/Si interface by Cu diffusion through the grain boundaries or local defects of the Zr–N barrier layer into Si substrate. In conjunction with sheet resistance measurement, XRD and XPS analyses, the Cu/Zr–Ti–N/Si contact system has high thermal stability at least up to 700°C. The incorporation of Ti atoms into Zr–N barrier layer was shown to be beneficial in improving the thermal stability of the Cu/barrier/Si contact system. [Copyright &y& Elsevier]

Abstract: Barrier capability of Zr–Si diffusion barriers in Cu metallization has been investigated. Amorphous Zr–Si diffusion barriers were deposited on the Si substrates by RF reactive magnetron sputtering under various substrate temperatures. An increase in substrate temperature results in a slightly decreased deposition rate together with an increase in mass density. An increase in substrate temperature also results in grain growth as deduced from field emission scanning electron microscopy (FE-SEM) micrographs. X-ray diffraction (XRD) spectra and Auger electron spectroscopy (AES) depth profiles for Cu/Zr–Si(RT)/Si and Cu/Zr–Si(300°C)/Si samples subjected to anneal at various temperatures show that the thermal stability was strongly correlated with the deposition temperature (consequently different density and chemical composition etc.) of the Zr–Si barrier layers. ZrSi(300°C) with higher mass density make the Cu/Zr–Si(300°C)/Si sample more stable. The appearance of Cu3Si in the Cu/Zr–Si/Si sample is attributed to the failure mechanism which may be associated with the diffusion of Cu and Si via the grain boundaries of the Zr–Si barriers. [Copyright &y& Elsevier]

Abstract: Zr–N/Zr bilayered film as a diffusion barrier between Cu and Si is evaluated. The thermal stability of the diffusion barrier is investigated by annealing the Cu/Zr–N/Zr/Si samples in N2 for an hour. XRD, SEM and AES results for the above contact systems after annealing at 700°C show that Cu film has preferential (111) crystal orientation and no diffraction peaks of Cu3Si and a Cu–Zr–Si ternary compound are observed for all Cu/Zr–N/Zr/Si contact systems. In addition, the atomic distribution of Zr and Si is evident and grows with increasing temperature up to 700°C, which corresponds to the Zr–Si phase having low contact resistivity. Low contact resistivity and high thermal stability diffusion barrier can be expected by the application of the Zr–N/Zr bilayered film as a diffusion barrier between Cu and Si. [Copyright &y& Elsevier]

The distribution of second-phase particles is crucial to the mechanical properties of particulate reinforced copper matrix composites (PRCMCs). Ultrasonic vibration treatment (UVT), as an effective technique to disperse second-phase particles in metallic melts, has been extended to treat PRCMCs using a SiAlON sonotrode. In this study, systematic experiments have been conducted to explore the effect of UVT on the microstructures and mechanical properties of in situ Cu-TiB 2 composites. The results indicated an optimal duration of UVT for 3 min, featured by an improved distribution of TiB 2 particles and superior mechanical properties of the as-cast composite. The ultimate tensile strength, yield strength, and elongation exhibited significant increases of 15.7%, 18.1%, and 36.1%, respectively, compared to the as-cast Cu-TiB 2 composite without UVT. Furthermore, these experimental composites were subject to rolling deformation. The results once again demonstrated that the as-rolled Cu-TiB 2 composite, treated with UVT for 3 min, stood out as the best. The ultimate tensile strength, yield strength, and elongation of the as-rolled Cu-TiB 2 composite were 459 MPa, 422 MPa, and 7.0%, respectively. Based on the microstructural observation, the mechanism underlying the UVT-induced enhancement of mechanical properties was discussed in terms of the non-linear effects of ultrasound cavitation on liquid metals. This work can provide a strategy for producing high-performance PRCMCs through UVT. • Cu-1 wt% TiB 2 composites are successfully prepared by combining UVT and in-situ synthesis. • UVT can eliminate TiB 2 particles from agglomerating and obtain homogeneous microstructure. • Ultrasonic-assisted in situ casting improves both the strength and ductility of Cu-TiB 2 composites. • The effect of UVT is positively related to time only in some time ranges. [ABSTRACT FROM AUTHOR]

The effectiveness of ZrSiN/Zr bilayered films to serve as diffusion barriers in Cu/Si contacts has been investigated. Annealing studies for Cu/ZrSiN/Zr/Si contact systems were carried out in N2/H2(10%) ambient. X-ray diffraction data suggest that Cu film has preferential (111) crystal orientation and Cu silicide cannot be observed up to 700 °C. Scanning electron microscopy micrographs show that the Cu film was integrated and free from agglomeration after annealing at 700 °C. Auger electron spectroscopy depth profiles of the Cu/ZrSiN(10 nm)/Zr(20 nm)/Si samples have no noticeable change except Zr silicide grows with annealing temperature up to 700 °C. The results indicate excellent barrier property for ZrSiN(10 nm)/Zr(20 nm) bilayer structure for Cu metallization. [ABSTRACT FROM AUTHOR]

Layered CuCrZr/Cu composites with different densities of gradient heterogeneous interfaces were designed and prepared by powder metallurgy combined with rolling and aging. The prepared layered CuCrZr/Cu composites achieved better comprehensive properties than the homogeneous CuCrZr alloy. The evolution of local strain was analyzed by high resolution digital image correlation (DIC). A strain-transfer from CuCrZr layer to adjacent Cu layers appears at the gradient heterogeneous interface, which relieves the strain localization of CuCrZr layers in layered CuCrZr/Cu composites. The incompatible deformation between the gradient heterogeneous microstructures across the layer interface leads to the generation and accumulation of geometrically necessary dislocations (GNDs), which results in extra work hardening and hetero-deformation induced (HDI) strengthening. The increase in the density of gradient heterogeneous interfaces can enhance the interface constraint behavior and produce a greater HDI strengthening effect, which tends to improve the work hardening ability and HDI stress of layered CuCrZr/Cu composites. Furthermore, various crack propagation modes of crack deflection, multiple cracks and crack blunting caused by uneven stress/strain partition at the gradient heterogeneous interface of layered CuCrZr/Cu composites were characterized by in-situ tensile tests. • Layered CuCrZr/Cu composites with different densities of gradient heterogeneous interfaces were designed and prepared by powder metallurgy combined with rolling and aging. • The in-situ digital image correlation (DIC) technique was used to visualize the local strain of layered CuCrZr/Cu composites and CuCrZr alloys, revealing the strain partitioning behavior caused by the non-synchronous deformation between CuCrZr and Cu layers. • The increase in the density of gradient heterogeneous interfaces can produce a greater hetero-deformation induced (HDI) strengthening effect, which tends to improve the work hardening ability and HDI stress of layered CuCrZr/Cu composites. • Various crack propagation modes of crack deflection, multiple cracks and crack blunting caused by uneven stress/strain partition at the gradient heterogeneous interface of layered CuCrZr/Cu composites were characterized by in-situ tensile tests. [ABSTRACT FROM AUTHOR]

Human activities have liberated substantial amounts of biologically active metals into oceans. However, identifying the sources and migration processes of these metals is challenging. Here we present first century‐long records of concentrations and isotope compositions of Zn and Cu (δ66Zn and δ65Cu) in two corals from the northern South China Sea. The results show dramatic enrichment in coral Zn and Cu concentrations since the 1980s, which coincide with δ66Zn and δ65Cu increases. Coupled with concurrent land use/cover changes, we suggest that the enrichment trends of Cu and Zn in corals are best explained by human‐induced rock weathering and soil erosion, which transferred isotopically heavy Zn and Cu fluxes into the coastal ocean. The metal releases due to land use/cover changes relative to direct anthropogenic sources could be even more significant in the future given that anthropogenic releases have been legally controlled and started to decline in recent decades. Plain Language Summary: Substantial amounts of biologically active but potentially toxic metals such as zinc and copper have been released into the Earth's surface due to increasing human activities. Most previous studies linked marine zinc and copper enrichment to direct human‐related releases that are transferred into oceans via atmospheric deposition and river discharge, but neglected natural releases that have been augmented by human activities. Here, we found that zinc and copper levels in annually banded corals from South China Sea coastal areas are increasing since the early 1980s, and these increasing trends are best explained by human‐induced rock weathering and soil erosion based on evidence from first measured isotope signatures and land use/cover changes. This pathway was largely overlooked before, but might be a predominant pathway accounting for marine metal enrichment in future given more and more strict environmental laws targeted at curbing metal releases by human activities. Key Points: The coral Zn and Cu isotopic compositions indicate progressive changes of Zn and Cu sources into the ocean through the timeUnprecedented enrichment of coastal Zn and Cu since the 1980s is associated with increases in δ66Zn and δ65CuHuman‐induced rock weathering and soil erosion mainly contributed increased fluxes of dissolved Zn and Cu [ABSTRACT FROM AUTHOR]

The nanocrystalline metallic bilayer structure can effectively enhance the strength of Cu alloy while maintaining excellent electrical conductivity. Based on the microstructure evolution of Cu/Ag alloy observed by transmission electron microscope (TEM), molecular dynamics (MD) simulations of Cu/Ag alloy with nanocrystalline metallic bilayer structure were established. The mechanical properties and deformation mechanisms of nanocrystalline Cu/Ag-bilayer alloys were investigated at different temperatures. A mixed Hall-Petch (H-P) relationship was observed between the ultimate stress and the increased layer thickness. In this paper, the deformation mechanism changes from dislocation accumulation at the Cu-Ag interface to dislocation through the Cu-Ag interface. In addition, the data analysis results of elastic modulus showed an approximately linear decrease trend with increasing temperature, and the deformation mechanism shifted from dislocation motion to a combination of dislocation motion and grain boundaries (GBs) diffusion. These findings provide guidance for the design of high magnetic field facility (HMFF) water-cooled magnets and very large-scale integration (VLSI) lead frames. • The deformation behaviour of the nanocrystalline Cu/Ag-bilayer alloy at different thicknesses (4–6 nm) and temperatures (1–800 K) is investigated. • The layer thickness of Cu/Ag-bilayer alloy conforms to the mixed H-P relationship. The mechanism changes from dislocation pile-up. • As temperatures increases, the deformation mechanism transformed from dislocation emission to a combination of dislocation motion and the high-temperature softening. [ABSTRACT FROM AUTHOR]

[Display omitted] • Performance of single crystal copper rod was improved by rare earth microalloying. • The interaction between rare earth Y and impurity P was established by Miedema model. • The precipitation behavior of Y and P was discussed. • The synergistic enhancement of mechanical and conductive properties was proposed. Single-crystal copper rods with high conductivity and mechanical properties are the decisive material for the production of microwires for chip bonding. To further improve the product of strength and elongation as well as electrical conductivity, rare earth Y is added to a single-crystal copper rod to adjust the microstructure and impurity state. The results show that Cu-0.03Y copper rods have excellent comprehensive properties. The electrical conductivity improves to 103.72 % IACS, and the product of strength and elongation improves to 8.772 GPa%. The precipitates in the Cu-0.03Y single crystal copper rod are nano-sized spherical particles composed of YP (NaCl type) and Cu 5 Y (Cu 5 Ca type) phases. The enthalpy of formation of Y and P is calculated using Miedema thermodynamics as ΔH = −173.45 kJ·mol−1. The precipitates formed by the preferential reaction of Y and P reduce the solid dissolved atoms in the copper, and the electrical conductivity increases accordingly. The 〈0 0 1〉 texture of a single-crystal copper rod decreases with the addition of Y, while the 〈1 0 1〉 texture increases with good plasticity, leading to an improvement in elongation. [ABSTRACT FROM AUTHOR]

Herein, a palladium-coated copper wire was prepared using a halogen-free direct coating process, and the effects of the coating temperature on the morphology of the palladium coating and the mechanical properties of the wire were studied. The structural characteristics of the coating and copper matrix as well as the diffusion, reaction, and bonding characteristics of the elements at the copper–palladium interface were investigated. Results show that the deposition rate of palladium and the aggregation of palladium grains were accelerated with increasing coating temperature, promoting the formation of large palladium particles on the surface of the palladium-coated copper wire. The strength of the coated wire decreases and the elongation increases with increasing coating temperature. At 400 °C, the thickness of the coating was approximately 51 nm coating, consisting of approximately 4 nm nanocrystals. The improvement in plasticity was attributed to the distortionless recrystallized subgrain nucleus formed by the cell structure comprising dislocation tangles in the copper matrix, which reduces the matrix dislocation density. Positive and negative edge dislocations were present in the coating, and the two dislocation lines of the edge dislocation dipole offset each other. Numerous crystal defects were found in the copper–palladium bonding interface zone. Moreover, copper unidirectionally diffuses into the palladium coating, forming the intermetallic-compound CuPd in the interface bonding zone. Furthermore, the formation of twins was caused by the change in the stacking order of atoms due to the stacking fault occurring on the crystal surface, and the thickness of the diffusion zone was approximately 9 nm. [Display omitted] • A uniform Pd coating with a thickness of 51 nm was obtained. • Diffusion and reaction behavior of Pd coating on Cu wire were explored. • Formation mechanism of Pd coating morphology was proposed. • Effect of temperature on the mechanical properties of the wire was discussed. [ABSTRACT FROM AUTHOR]

• Ultrasonic waves were successfully introduced into Cu-TiB 2 melt at 1523 K. • The deagglomeration and dispersion of TiB 2 were achieved by ultrasonic treatment. • The strength and ductility were improved concurrently after ultrasonic treatment. In this paper, ultrasonic vibration treatment (UVT) was directly introduced into Cu-Ti-B melt through a Sialon sonotrode. The effects of UVT on the microstructures and properties of TiB 2 /Cu composite thus fabricated were investigated. The results indicate that with the application of UVT, the average size of the particle agglomerates in the as-cast composite reduced from 24.84 μm to 19.69 μm. Besides, the 3D morphology of the agglomerates changed from irregular to near-spherical under the effect of ultrasound cavitation. The acoustic streaming promotes the flow of the melt to realize a more uniform distribution of particles in the bulk. Dispersion of TiB 2 particles alleviates the stress concentration caused by coarse agglomerates, resulting in the concurrent improvements in both strength and ductility of the composite. [ABSTRACT FROM AUTHOR]

This work aims to investigate the electrical sliding wear behavior of the dual-scale particulate reinforced copper matrix composites by a self-developed pin-on-disk wear tester. Cu- x Cr-0.3Zr-1ZrB 2 (x = 0, 0.5, 1.0) composites were fabricating by casting and cold rolling. The microstructure of worn surfaces was examined using scanning electron microscopy (SEM) and laser scanning confocal microscope to unravel the wear mechanisms. The results indicated that the combined effect of mechanical wear and electrical wear dominated the wear process with an increase in the apparent normal load. Amplifying the electrical current increased the wear loss of the sliding pair, in the meantime alleviated the fluctuation of the friction coefficient with marginal changes in the average values. After introducing Cr element and ZrB 2 particles, the wear rate decreased from 0.197 mg/m to 0.141 mg/m under moderate operating test conditions. Adhesive wear and abrasive wear occupied an important position in the wear mechanism of the Cu-1wt%Cr-0.3wt%Zr-1wt%ZrB 2 composite under electrical current due to the elevation of thermal stability and the formation of a tribolayer introduced by these reinforcements. [Display omitted] • The Cu-1Cr-0.3Zr-1ZrB 2 composite stands out with the best tribological properties. • High apparent contact load changes the wear mechanism from abrasive to arc erosion. • Amplifying the electrical current results into the increased Joule and arc heat effects. [ABSTRACT FROM AUTHOR]

Abstract: Films of Cu/Cu(Ru) and Cu(Ru) were deposited on Si substrates by magnetron sputtering. Samples were subsequently annealed and analyzed by four-point probe (FPP) measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). After annealing at 500°C, resistivity values of both systems decrease, but the reduction is more significant for Cu(Ru). Moreover, the resistivity values of annealed Cu(Ru) film are still greater than those of annealed Cu/Cu(Ru) film. XRD data suggest that Cu/Cu(Ru) film has higher thermal stability and Cu silicide cannot be observed up to 500°C. According to TEM results, after annealing at 500°C, the grain size of the Cu(Ru) film is smaller than that of Cu/Cu(Ru) film. In conjunction with AES, XRD, TEM analyses and sheet resistance measurement, it indicates that Cu/Cu(Ru) seed layers are potentially good for advanced Cu interconnects from the views of interfacial stability and low resistivity. [Copyright &y& Elsevier]