Copper Grain Size Research Articles

Grain Size, Misorientation, and Texture Evolution of Copper Processed by Equal Channel Angular Extrusion and the Validity of the Hall–Petch Relationship

The microstructure and texture of copper subjected to equal channel angular extrusion (ECAE) via route B C for up to 16 passes have been assessed using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), X-ray diffraction (XRD) peak broadening, and texture analysis. The differences in grain size measured by these techniques allows for an understanding of microstructural evolution. A gradual decrease in grain size occurs with an increasing number of passes, while the subgrain size remains approximately constant. Up to four passes, the fraction of high-angle grain boundaries (HAGBs) (>15 deg) increases from 15 to 45 pct, but remains constant thereafter. The grain boundary character distribution shows a decrease of Σ1 boundaries and an increase of Σ3 boundaries with higher passes. After 16 passes, a few regions of large 1 to 4 μm sized grains embedded in a submicrometer sized matrix were observed. These agglomerates of larger grain diameters together with the measured decrease in the dislocation density correlate with the observed decrease in yield strength of samples subjected to four and more passes. Texture evolution is adequately described under conditions of negative simple shear. The effect of increased accumulated strain results in an overall spread of orientation densities due to the absence of stable end positions post-ECAE. Detailed microstructural information suggests that strengthening mechanisms in the material can be sufficiently well described by the classical Hall–Petch relationship by applying it to the subgrain size, while the subgrain size remains smaller than the grain size.

Morphologies of copper deposits obtained by the electrodeposition at high overpotentials

Morphologies of copper deposits obtained at overpotentials belonging to the plateau of the limiting diffusion current density and at higher overpotentials were examined by the scanning electron microscopy (SEM) technique. Copper dendrites are formed at overpotentials belonging to the plateau of the limiting diffusion current density. The shape of copper dendrites depends on the electrodeposition overpotential. At higher overpotentials (800 and 1000 mV) and larger values of current densities, porous and very disperse copper deposits were obtained. These morphologies were a consequence of a very vigorous hydrogen evolution at these electrodeposition overpotentials. Also, the obtained copper structures consisted of agglomerates of copper grains. The size of copper grains is a function of the overpotential of electrodeposition, thus approaching to nano-sized dimensions is achieved when the electrodeposition overpotential is increased.

Photocatalytic reduction of CO 2 on copper-doped Titania catalysts prepared by improved-impregnation method

Photocatalytic reduction of CO 2 by copper-doped titania catalysts has been investigated. The photocatalysts with various copper species (Cu 0, Cu I, Cu II) were prepared by an improved-impregnation method, where copper nitrate is doped into TiO 2 Degussa-P25. It is likely that copper present on the catalyst surface and the grain size of copper–titania catalysts is uniform, with crystallite size approximately 23 nm. The dispersion capacity of CuO in the vacant sites of TiO 2 is about 4.16 Cu 2+ nm −2 (≈2.2 wt% of Cu), as indicated by XRD analysis. The activation energy ( E a) for Degussa-P25 and 3%CuO/TiO 2 is ca. +26 and +12 kJ/mol, respectively. These E a values suggest that the desorption event is a rate limiting step, and the lower E a of 3%CuO/TiO 2 may suggest a catalytic role of copper species that enhance the methanol production.

On the Stability of Defects and Grain Size in Ultrafine-Grained Copper during Cyclic Deformation and Subsequent Ageing at Room Temperature

Ultrafine-grained (UFG) pure Cu processed by equal channel angular pressing (ECAP) was subjected to cyclic deformation and subsequent ageing treatment at room temperature (RT) in order to investigate the stability of defects and grain size. Cyclic deformation for 1000 cycles at RT leads to a large decrease of internal stress. X-ray diffraction (XRD) shows that the stability of defects and grain size at RT in as-cyclic deformed sample is lower than that in as-processed sample and that a reduction of internal stress takes place prior to grain growth. TEM observations show that the microstructural evolution during ageing is characterized by normal grain growth accompanied with recovery within grain interior.

Effects of additives and chelating agents on electroless copper plating

In this study, ethylenediaminetetraacetic acid (EDTA), triethanolamine (TEA), and ethylenediamine (En) were adopted herein as additives or chelating agents in electroless copper plating, with formaldehyde as the reduction agent. Linear sweep voltammetry was successfully applied to analyze the potential shift of copper complexes and the adsorption capability of chelating agents on a surface. Moreover, the grain size and surface roughness of copper were investigated using atomic force microscopy (AFM). The experimental results for a dual-chelating-agent system indicated that EDTA plays an important role in chelating, while the main effect of TEA is adsorption on copper surfaces to inhibit formaldehyde oxidation. Meanwhile, ethylenediamene is a prominent refining agent owing to its markedly higher adsorption strength on copper surfaces than formaldehyde and TEA. The analyses including linear sweep voltammetry, AFM, and XRD are effective to explore the effect of chelating agents and additives on electroless copper plating and deposits.

Trench and Via Filling with Electroplated Copper: Effect of Current Density and Pulse Waveform

AbstractA study was carried out to investigate the effect of current density and pulse waveform on the filling of line trenches and contact vias with aspect ratio of 2:1 for sub-0.25 µm device manufacturing using normal pulse plating of copper. The growth pattern of the copper films deposited using 0.05 and 0.10 A/cm2 current density gave no significant difference. Small grains were seen to have nucleated uniformly across the line trenches and via holes after 1 second of electroplating. With increasing the deposition time to 2 seconds, a slight buildup of the film thickness was observed in both trenches and vias without significant increase in the size of the copper grains. Grain growth involving the coalescence of small grains occurred after 5 seconds of plating and a further buildup in thickness and fill up of the trenches and vias occurred after 10 seconds of deposition.When the patterned wafers were plated with a pulse waveform of 3 ms on and 0.5 ms off, the filling of trenches could not be complete after 30 seconds of electroplating. A complete filling of the trenches was achieved within 30 seconds of deposition using a pulse waveform of 6 to 8 ms on and 1 to 2 ms off. When the on-period was increased above this range to 9.9 ms, voids were observed at the centre of the via holes.

Dislocations, grain size and planar faults in nanostructured copper determined by high resolution X-ray diffraction and a new procedure of peak profile analysis

The particle size and the dislocation structure in inert gas condensed nanocrystalline copper were determined by high-resolution X-ray diffraction profile analysis. Well-behaved smooth curves were obtained in the modified Williamson–Hall plot and the modified Warren–Averbach plot through knowledge of the variation in dislocation contrast with Bragg reflection and the effect of twinning on particle size. The particle size was between 14 and 30 nm, in agreement with TEM results. The root-mean-squared strains were explained by the presence of dislocations, with a dislocation density of about 5×10 15 m −2. The dislocations were found to have screw character probably related to the particle growth mechanism.

A comparison of shaped charge liner cone and recovered jet fragment microstructures to elucidate dynamic recrystallization phenomena

In several previous publications, we have argued that reductions in the starting grain size of copper [l] and tantalum [2] shaped charge liner cones by as much as a factor of 102 in recovered slug and jet fragments following detonation provided unambiguous evidence for dynamic recrystallization (DRX) as proposed earlier by Meyers, et al 13, 41. This evidence was based upon the fact that such a dramatic grain refinement (from roughly 35 pm to 0.3 pm) could only be explained by DRX especially in cases where the grain boundary misorientations averaged >15O. Furthermore, Chokshi and Meyers [4] argued that treatments of DRX by Sandstrom and Lagneborg [5] and Derby and Ashby [6] had developed similar expressions for a steady-state grain size proportional to the reciprocal square root of the strain rate. They utilized this proportionality along with other related assumptions to arrive at steady-state grain sizes between 0.1 and 0.01 pm for copper having undergone DRX at strain rates above 104 s-1.

Characterization of Films Formed during the Corrosion of Copper in Dilute Solutions of Cupric Chloride

ABSTRACTMicrostructural differences in copper deposited by four techniques commonly used in the microelectronics industry were previously reported. Grain size, preferred orientation, and near surface chemistry were considered. [1] Prediction of the reaction rates were made based on these differences and then correlated with actual measurements. [2] In aerobic conditions the grain size dictated the reaction rate, the smaller the size the faster the rate.[3] The composition of the surface film formed during etching was examined. The trends in chemical concentrations on the surface film vary for each sample, but the relative constituent amounts correlate to the grain size of the original copper samples. Thus, there is further evidence that during exposure to aqueous solutions of cupric chloride, copper corrosion, in terms of both etch rate and film composition, is dictated by grain size of the original copper and not other microstructural factors.

Ultrasonic characterization of the effect of cold work and grain size in copper and 68:32 brass sheets

The effectiveness of ultrasonic velocity measurements was evaluated as a means for nondestructive characterization of cold-rolled copper and 68:32 brass sheets. An apparatus was designed to generate and receive the zeroth symmetrical mode of ultrasonic Lamb waves in thin copper and brass sheets. The effect of angular variations in propagation direction with respect to the rolling direction on the measured Lamb wave velocities is shown. Interpretation of the variations of ultrasonic Lamb wave velocity were related to deformation mechanisms and texture development in copper and 68:32 brass sheets. Results show that the grain size and cold work influence the velocity as well as the texture of copper and 68:32 brass sheets. Results indicate the possibility of using ultrasonic Lamb wave velocity as a tool to monitor elastic anisotropy.

Ultrasonic characterization of the effect of cold work and grain size in copper and 68:32 brass sheets

Ultrasonic characterization of the effect of cold work and grain size in copper and 68:32 brass sheets

Effect of grain size on high strain rate deformation of copper

Experiments were performed to observe the deformation characteristics of oxygen-free high-conductivity (OFHC) copper at high strain rates (up to 40,000 s−1) and to relate differenc in grain size with differences in deformation behavior. The rod impact and torsional Hopkinson bar test methods were used in these experiments. Results show that grain size reductions substantially reduce surface irregularities that develop during deformation. The effect of grain size on the yield stress and on the strain-hardening behavior of copper is small and is similar to the effect of grain size in copper at quasistatic strain rates. The observation that grain size has a substantial effect on surface irregularities may have important implications for applications in which stable deformation of thin sections is of concern.

On the determination of grain size in copper and aluminium by X-ray diffraction

Grain size determination for samples having grains coarser than 10 −4 cm is done by rotating the sample around specimen normal and counting the number of spots on Debye rings. A better agreement with metallography is obtained in the present analysis than the existing method of normal exposure.

The influence of grain size on the erosion rate of metals

The objective of this work was to understand the influence of grain size on solid impingement erosion behavior characterized by deformation at high strain rates and large strains. Experiments were carried out at a velocity of 40 m/s, impact angle of 90 deg with 300 to 450 μm steel shot as erodent on iron, copper, and titanium with varying grain sizes. The results indicate that the erosion rate is independent of grain size in iron and copper while it is apparently grain size dependent in titanium. The results are rationalized in terms of the negligible contribution of the Hall-Petch component to the flow stress at large strains in the case of copper and iron. The decreasing erosion rate in titanium with increasing grain size was due to the increased interstitial content picked up during thermal treatment and consequent increase in strain hardening and strain rate hardening and not due to increased grain sizeper se. Adiabatic shear bands were observed in coarse-grained iron under actual erosion conditions.

銅線の軟化特性に及ぼす熱間圧延銅線製造方法と不純物の影響

The softening characteristics of cold-drawn pure copper wires were studied in relation to hot-working processes and impurities of hot worked Cu wire rods. The characteristics of several kinds of hot-rolled wire rods were examined by means of structural observations, tensile tests and electrical resistivity measurements. The softening characteristics of cold-drawn copper wires were obtained from spring elongation tests and electrical resistivity measurements of 90% cold-drawn wires.It was found that the grain size and Cu2O particle size of the continuous casting and rolling rod (SCR: Southwire Continuous Rod) were the smallest and its Cu2O particle distribution was uniform. On the other hand, the grain size of Oxygen Free Copper (OFC) wire rod was the largest and its electrical conductivity was the highest. SCR cold-drawn copper had the lowest softening temperature. Specimens of copper wires could be arranged according to the order of softening tendencies by annealing:\ oindentSCR>TPC 1(normal Tough Pitch Copper)>OFC>TPC 3(Tough Pitch Copper with 16 ppm Pb and 11 ppm Sn).\ oindentA large amount of annealing twins was observed in the SCR wires.From these experimental results, the softening characteristics of the cold-drawn copper wires are considered to be related to metallurgical structure which depends on the hot-working processes and purities.

Grain refinement of copper by the addition of iron and by electromagnetic stirring

The effect of iron additions in the range of 0.57 to 7.5 wt pet on the grain size of electromagnetically levitated copper-iron alloys was investigated. The samples were solidified while levitated or quenched in water from the molten state. The addition of iron was found to be effective in reducing the grain size of copper, and the average grain size decreased as the iron content was increased up to the peritectic liquid composition of about 2.8 wt pet Fe. Beyond this composition, the grain size of the samples solidified in the levitated state was insensitive to the iron content, whereas that of the quenched samples continuously decreased with increasing iron content. The results indicate that electromagnetic stirring causes fragmentation of copper dendrites in the hypoperitectic region, and hence enhances grain refinement. In the hyperperitectic region, on the other hand, the stirring has a detrimental effect on the grain refinement by agglomerating the primary iron particles which act as heterogeneous nucleation sites for the copper matrix.

Grain size and high-temperature yield strength of polycrystalline copper

Polycrystalline, electrolytic tough pitch copper was prepared in a series of stable grain structures by deforming at 540 and 600°C at strain rates from 7.5 × 10−4 to 8 × 10−2 S−1. By applying a prestrain of 0.4 and annealing isothermally, grain sizes ranging from 0.056 to 0.810 mm were produced. The prepared grain sizes decreased with the amount and strain rate of the prestrain, and increased with the prestraining and annealing temperature. After working and sufficient annealing to permit full recrystallization, the yield strengths were determined at 540°C (0.6T m) and at four strain rates ranging from 7.5 × 10−4 to 8 × l0−2 S−1. The high-temperature yield strength increased linearly with the inverse square root of the grain size, as it does at room temperature. However, the grain boundary strength coefficient (slope of the Hall-Petch plot) increased with strain rate, indicating that the grain boundaries serve as both local and long-range obstacles to flow at elevated temperatures.

Tensile strength and work hardening of ultrafine-grained high-purity copper

Sputter-deposited high-purity copper specimens with grain sizes from 8.4 to 0.056 μm were tested in tension to investigate the influence of grain size on yield strength for small grain sizes. The smallest grain size in the sputter-deposited copper was a factor of 40 smaller than the smallest grain size previously available for yield-strength–grain-size studies of high-purity copper. The 0.2% offset yield strengths varied from 73.4 MPa for the coarsest-grained copper to 481 MPa for the finest-grained copper. The hardening was related to grain- and twin-boundary spacings. The yield strength obeyed the Hall-Petch relation even for the finest grain size of 0.056 μm, giving σy=6.39+3.74(l̄)−1/2 MPa, where σy is the 0.2% offset yield strength and l̄ is the mean intercept length (mm) between boundaries. The data agreed with the Ashby model, σ∼ (ε/l̄)1/2, only at very low strains (ε<0.001) for the specimens with very fine grain sizes (l̄⩽0.077 μm).

Origins of Nondestructive Readout of Plated Wires

The nondestructive readout (NDRO) capability of 3650-Å-thick Permalloy electroplated onto a variety of substrates has been evaluated using an on-line Belson test. The NDRO quality is evaluated using, not only the wall motion coercive force, but also the write threshold, the read only limit, Hk and the signal output. Various combinations of physical roughness and grain size of copper and gold substrates are compared. On smooth very fine grained Au substrates low dispersion and low coercive force films are produced which are not suitable for NDRO; with increasing grain size and roughness the NDRO quality improves. A substantial further improvement in NDRO quality is obtained by producing a new kind of substrate surface; namely, a surface composed of Au islands on rough Cu. The same small quantity of Au deposited on a smooth, finer grain Cu, although better than Permalloy deposited on the smooth very fine grain Au, is not as good as Permalloy directly on rough Cu. The presence of Au islands is confirmed from scanning electron micrographs and electrochemical measurements. Their effect on the magnetic properties is believed to be due to the additional roughness and to the fluctuation in Permalloy composition they produce. The composition fluctuations and stress in the Permalloy provide high anisotropy regions needed to prevent local saturation and therefore provide the restoring force, through coupling with the remainder of the film, to return the magnetization to its original direction.