Substrate effect on electrodeposited copper morphology and crystal shapes
TL;DR: In this paper, the surface morphology varies with the change in overpotential, but not with change in substrate, and the crystal shape is independent of the applied over-potential but varies with bath chemistry or choice of substrate.
Abstract: Copper has been electrodeposited on copper (FCC) and mild steel (BCC) substrates from acidic sulphate bath with and without cetyl trimethyl ammonium bromide at 0.25, 2, 6 and 9 V. It is found that the surface morphology varies with the change in overpotential, but not with the change in substrate. On the contrary, the crystal shape is found to be independent of the applied overpotential, but varies with the bath chemistry or choice of substrate.
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4 citations
TL;DR: In this article , a comparison between Cu/TiNT and TiNT is done based on the characterization techniques of scanning electron microscopy, X-ray Diffraction, Transmission Electron Microscopy, x-ray photoelectron spectroscopy and UV-Diffuse Reflectance Spectroscopy, and the result shows that the ethylene formation on the Cu deposited surface is favorable than the methane which is in line with the experimental observation.
3 citations
01 Jun 2021
TL;DR: In this article, the formation of epitaxial and non-epitaxial Cu/Cu/Cu interfaces in stacked blind micro via interconnections (BMVs) is investigated.
Abstract: A key factor in achieving high electrical reliability in multilayer HDI PCBs is the integrity of the target pad - electroless Cu - electrolytic Cu interface (Cu/Cu/Cu-interface), especially in stacked blind micro via interconnections (BMVs). In the present paper it is shown, that aside from a low density of nanovoids, the formation of epitaxial Cu/Cu/Cu interfaces is important in satisfying the highest reliability requirements. Using example microstructures that are typical to stacked BMVs, the post-plating formation of epitaxial and non-epitaxial interfaces are described through the concept and mechanisms of “bottom-up” and “top-down” recrystallization. Epitaxial Cu/Cu/Cu interfaces typically form through unhindered “bottom-up” recrystallization across both interfaces and penetrate deep into the electrolytically deposited Cu layer (ECD Cu). The ability of thin electroless Cu layers ( $1\ \mu\mathrm{m}$ of plated ECD Cu, greatly reduces the ability for “bottom-up” recrystallization to occur, and typically gives rise to an alignment of grain boundaries in this region. Failure analysis carried out after reliability testing has shown that such alignment of grain boundaries can be causative for a premature crack formation, and based on these findings, a fatigue-like crack formation mechanism is proposed, and recommendations given to improve the epitaxy of Cu/Cu/Cu interconnections.
2 citations
Cites background from "Substrate effect on electrodeposite..."
...In particular, the density of (100) and (111) facets on the Eless Cu surface seems to have a crucial impact on the adsorption and codeposition of ECD additives [9]....
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TL;DR: In this paper, the effects of hard particle friction under strong cathodic polarisation in an additive-free bath were investigated for the preparation of ultrafine-grained (UFG) Cu deposits.
Abstract: Ultrafine-grained (UFG) Cu deposits were prepared using pulse electrodeposition assisted by hard particle friction under strong cathodic polarisation in an additive-free bath. The effects of hard p...
2 citations
Cites background from "Substrate effect on electrodeposite..."
...during electrodeposition is related to the difference in the crystal growth rate and the surface energy [16]....
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...purposes of grain refinement is typically avoided given that the quality of deposits is strongly dependent on the polarisation [16]....
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01 Aug 2019
TL;DR: The needle structure plays a key role in the new low-temperature bonding technology as discussed by the authors and a electrodeposition route was used to directly obtain large copper needles up to the micron size.
Abstract: The needle structure plays a key role in the new low-temperature bonding technology. A electrodeposition route was used to directly obtain large copper needles up to the micron size. The copper needle was hexagonal pyramid with (111) preferred orientation. In order to regulate the size and density of copper needles, the effects of various electrodeposition methods and additives were studied. The slower the sweep speed of linear sweep voltammetry, the longitudinal growth was much faster than lateral growth. And with the scanning interval lengthening, copper needles changed from needle-like to columnar and then into broccoli. When adopted the galvanostatic method or cyclic voltammetry respectively, copper needles became larger as the current density or the number of cycles increased. The higher the frequency in pulse method, the copper needles were no longer obvious. Accelerators can increase the nucleation of copper needles for higher density, while both inhibitors and levelers were detrimental to copper needles.
2 citations
Cites background from "Substrate effect on electrodeposite..."
...It was caused by excessive overpotential because the growth rate no longer had a significant difference in all directions([22])....
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References
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12 Jun 1951-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this paper, it was shown that the rate of growth of a surface containing dislocations is proportional to the square of the supersaturation for low values and to the first power for high values of the latter.
Abstract: Parts I and II deal with the theory of crystal growth, parts III and IV with the form (on the atomic scale) of a crystal surface in equilibrium with the vapour. In part I we calculate the rate of advance of monomolecular steps (i.e. the edges of incomplete monomolecular layers of the crystal) as a function of supersaturation in the vapour and the mean concentration of kinks in the steps. We show that in most cases of growth from the vapour the rate of advance of monomolecular steps will be independent of their crystallographic orientation, so that a growing closed step will be circular. We also find the rate of advance for parallel sequences of steps. In part II we find the resulting rate of growth and the steepness of the growth cones or growth pyramids when the persistence of steps is due to the presence of dislocations. The cases in which several or many dislocations are involved are analysed in some detail; it is shown that they will commonly differ little from the case of a single dislocation. The rate of growth of a surface containing dislocations is shown to be proportional to the square of the supersaturation for low values and to the first power for high values of the latter. Volmer & Schultze’s (1931) observations on the rate of growth of iodine crystals from the vapour can be explained in this way. The application of the same ideas to growth of crystals from solution is briefly discussed. Part III deals with the equilibrium structure of steps, especially the statistics of kinks in steps, as dependent on temperature, binding energy parameters, and crystallographic orientation. The shape and size of a two-dimensional nucleus (i.e. an ‘island* of new monolayer of crystal on a completed layer) in unstable equilibrium with a given supersaturation at a given temperature is obtained, whence a corrected activation energy for two-dimensional nucleation is evaluated. At moderately low supersaturations this is so large that a crystal would have no observable growth rate. For a crystal face containing two screw dislocations of opposite sense, joined by a step, the activation energy is still very large when their distance apart is less than the diameter of the corresponding critical nucleus; but for any greater separation it is zero. Part IV treats as a ‘co-operative phenomenon’ the temperature dependence of the structure of the surface of a perfect crystal, free from steps at absolute zero. It is shown that such a surface remains practically flat (save for single adsorbed molecules and vacant surface sites) until a transition temperature is reached, at which the roughness of the surface increases very rapidly (‘ surface melting ’). Assuming that the molecules in the surface are all in one or other of two levels, the results of Onsager (1944) for two-dimensional ferromagnets can be applied with little change. The transition temperature is of the order of, or higher than, the melting-point for crystal faces with nearest neighbour interactions in both directions (e.g. (100) faces of simple cubic or (111) or (100) faces of face-centred cubic crystals). When the interactions are of second nearest neighbour type in one direction (e.g. (110) faces of s.c. or f.c.c. crystals), the transition temperature is lower and corresponds to a surface melting of second nearest neighbour bonds. The error introduced by the assumed restriction to two available levels is investigated by a generalization of Bethe’s method (1935) to larger numbers of levels. This method gives an anomalous result for the two-level problem. The calculated transition temperature decreases substantially on going from two to three levels, but remains practically the same for larger numbers.
4,432 citations
TL;DR: A review of the present status of the problem of metal deposition and electrochemical phase formation and growth is made in this paper, with an overview of the major contributions of different electrochemical schools.
407 citations
TL;DR: In this paper, the effect of hydrogen codeposition on the morphology of copper electrodeposits was studied and the dependences of the overall current and the volume of evolved hydrogen on the quantity of electricity used were plotted and the average current efficiencies of the evolved hydrogen were derived from them.
191 citations
Abstract: 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.
172 citations
TL;DR: In this article, the influence of current density on microhardness through its effect on grain size has been found to obey the Hall-Petch relationship in the nanometer range.
Abstract: Thin copper-electrodeposited films have been prepared on steel substrates from an additive-free copper sulfate bath by applying different current signals such as rectangular and square wave pulses, triangular waveform and also by direct current with variation of its magnitude. Mechanical properties of these films have been studied by means of dynamic microindentation measurements known as the universal microhardness test. Values of the hardness, plastic component, Young's modulus and percent of elastic recovery have been measured. In order to obtain the preferential orientation and grain size of the electrodeposits, X-ray diffraction studies have been made as well as scanning electron microscopy to evaluate their morphology. All the deposits showed a preferential orientation but without a simple correlation with the mechanical features of the films. The influence of current density on microhardness through its effect on grain size has been found to obey the Hall–Petch relationship in the nanometer range. Finally, correlations between the mechanical properties of the electrodeposits and the electrodeposition parameters have been made. These kinds of studies raise the possibility of tailoring films with good mechanical performance for different technological applications just by selecting the appropriate electrodeposition conditions.
112 citations