Validity of the Linear Growth Equation for Interface Evolution for Copper Electrodeposition in the Presence of Organic Additives (original) (raw)
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Interface dynamics for copper electrodeposition: The role of organic additives in the growth mode
2002
An atomistic model for Cu electrodeposition under nonequilibrium conditions is presented. Cu electrodeposition takes place with a height-dependent deposition rate that accounts for fluctuations in the local Cu 2ϩ ions concentration at the interface, followed by surface diffusion. This model leads to an unstable interface with the development of protrusions and grooves. Subsequently the model is extended to account for the presence of organic additives, which compete with Cu 2ϩ for adsorption at protrusions, leading to a stable interface with scaling exponents consistent with those of the Edwards-Wilkinson equation. The model reproduces the interface evolution experimentally observed for Cu electrodeposition in the absence and in the presence of organic additives.
Langmuir, 1998
Changes in the topography of Cu electrodeposits grown on polycrystalline Cu substrates at low constant current density from still aqueous concentrated CuSO4 + H2SO4 solutions, at 298 K, were studied by scanning force microscopy (SFM) at different scale lengths (L) from the nanometer level upward. The dynamic scaling theory applied to SFM images leads to exponents R) 0.87 (0.06 and) 0.63 (0.08, which are consistent with an interface growing under an unstable regime. For similar conditions, the addition of 1,3-diethyl-2-thiourea reduces the average crystal size (〈ds〉) of electrodeposits leading to scaling exponents R) 0.86 (0.06 and) 0.24 (0.05 for L < 〈ds〉 and a logarithmic dependence for the spatial and temporal evolution of the interface for L > 3 µm and t f 0. In an additive-free plating bath, the unstable growth regime appears to be originated by enhanced electrodeposition at protrusions due to curvature effects and further sustained by the electric and concentration fields built up around the growing deposit. The presence of the additive hinders the development of instabilities driving the evolution of the growing interface to that predicted by the Edwards-Wilkinson growth model on the asymptotic limit.
Physical Review B, 2000
The interface dynamics of metal electrodeposits in the presence of organic additives is followed in twodimensional glass cells. Stable Cu interfaces are formed at intermediate thiourea concentrations when a critical, but small surface coverage of thiourea ͑͒ is reached. For values corresponding to a close-packed adsorbate, the interface again becomes unstable because Cu growth takes place at defective sites in the adsorbed layer. The ability of additive molecules to suppress unstable growth is related to the formation of a diluted twodimensional gas-like surface state preferentially adsorbed at protrusions. Protrusions are more efficient for capturing the additive than valleys, as additive molecules arrive at the growing deposit under diffusion control from the solution.
Evolution of the Growth Front for Copper Electrodeposition Followed by Real Time Imaging
Langmuir, 1998
The interface motion for Cu electrodeposition in additive-free and thiourea-containing acid plating baths using three-dimensional and quasi-two-dimensional electrochemical cells was followed in real time in the potential range where the kinetics of the reaction is dominated by activation and Ohmic overpotentials. In the additive-free plating bath the growing interface changes from a marginally stable (nodular) to an unstable (branched) regime as the activation overpotential/Ohmic overpotential ratio decreases. The presence of thiourea drives the interface motion to a steady-state regime in which the predictions of the Edwards-Wilkinson equation for the interface motion are obeyed. The influence of thiourea on Cu electrodeposition is to slow the growth rate at protrusions and to increase the growth rate at flat surface domains or valleys, leading to a smoothing of the entire growing electrodeposit surface.
Journal of Applied Electrochemistry, 1996
Electrochemical measurements were carried out simultaneously with acquisition of in situ STM images of copper electrodeposition at low cathodic overpotentials and subsequent dissolution from the underlying polycrystalline gold surfaces. The morphologies of the copper deposits were examined for correlation with features of the current-voltage diagram. Copper growth is by nucleation and formation of 3D islands. During the initial stages of
Thin Solid Films, 2004
Injecting an in-plane current by connecting the two ends of a thin Au film to different potentials relative to a common reference couple results in the formation of a linear potential gradient at the surface of the electrode. Coupling the surface potentials to a redox species in solution then causes spatially dependent redox chemistry, effectively mapping the electrochemical reaction onto the surface. Copper was selectively deposited to the surface of the Au film by selecting applied potentials that encompass E eq for the Cu 2 + /Cu 0 reduction. Upon potential application copper deposits onto the area of the electrode for which V(x)< E eq , while the areas with local potentials positive of E eq contained no observable Cu. A transition region is established on the surface in an area corresponding to the anodic peak (strip-out) potential. Careful calibration of the surface electrochemical potential gradient indicates that the transition occurs at ca. 116 mV in agreement with an anodic peak potential centered at ca. 125 mV vs. Ag/AgCl from cyclic voltammetry. The width of the interfacial region analyzed by Auger electron spectroscopic line profiling and atomic force microscopy (AFM) is found to be dramatically sharper than expected. For a reversible two-electron process the development of surface composition based on a Nernstian local potential would yield a transition region f 59/2 mV wide. Translated to the spatial domain the interfacial width should be f 243 Am when a 123 mV/mm electrochemical potential gradient is imposed. Auger and AFM data confirm the interfacial width is strikingly smaller-by a factor of approximately 10-strongly suggesting that either the local electrochemical potential, V(x), is altered significantly upon Cu deposition, or V(x) alone is not responsible for the sharpness of the interface.
Microstructure in electrodeposited copper layers; the role of the substrate
Electrochimica acta, 2001
The microstructures of Cu layers, ranging in thickness from 3 to 12 mm, were investigated. The layers were electrodeposited from an acidic copper electrolyte onto two distinct substrate materials important for the micro-components industry: an Au layer with a pronounced 111-texture, and a nano-crystalline Ni P layer. The evolutions of surface topography, morphology and crystallographic texture in the layers were investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction analysis, respectively. Distinct surface topographies were observed for Cu layers deposited on the Au and Ni P substrates. Deposition onto the Au substrate resulted in a very smooth surface of all Cu layers, whereas the Ni P substrate caused an irregular surface for 3-mm-thick layers of Cu. The crystallographic texture in the Cu layers in the first few micrometres depended strongly on the crystallographic texture in the substrate. The Cu crystallites inherited the 111-orientation of the Au substrate, whilst no preferred crystallographic orientation was observed in the Cu crystallites on the nano-crystalline Ni P substrate. For Cu layers thicker than 3 mm a 110-fibre texture developed on both the substrates.
Experimental aspects of dense morphology in copper electrodeposition
Physical Review A, 1991
We report an extensive study of electrochemical deposition of copper with growth under galvanostatic conditions and parallel geometry. In such conditions a clear understanding of the origin of the ramified deposit and of its growth speed is possible, at least in the case of dense morphology. We confirm that this morphology belongs to a steady-state regime where growth can be modeled as the displacement of a Hat strip of nearly equipotential copper. The growth velocity is exactly the drift velocity of the anions, which is proportional to the current density. We also show that the mass of the deposit does not depend on the speed at which it was grown but only on the concentration of salt in the bulk of the electrolyte. We compute the modifications in concentration profiles and in the electric field due to pH changes during growth.
Dynamical growth behavior of copper clusters during electrodeposition
Applied Physics Letters, 2010
Ultrahigh resolution full-field transmission x-ray microscopy enabled us to observe detailed phenomena during the potentiostatic copper electrodeposition on polycrystalline gold. We detected two coexisting cluster populations with different sizes. Their growth behaviors are different, with a shape transitions only occurring for large clusters. These differences influence the micromorphology and general properties of the overlayer.
Molecular dynamics simulation of surface morphology during homoepitaxial growth of Copper
The European Physical Journal Applied Physics, 2019
In this paper, molecular dynamics (MD) simulation of surface morphology during homoepitaxial growth of Copper was investigated. For this purpose, simulations of Cu deposition on the Cu(111) substrate with an incidence energy of 0.06 eV at 300K were performed using the embedded-atom method (EAM). The grown thin film on Cu(111) reveled a rough surface morphology. During deposition, the important fraction of atoms intended for the upper layers undergone a rising rate of about 40% starting from the 2nd period and continued to increase until 65%, while the lower level reached a permanent rate of only 25% by the 4th period. Otherwise, except at the first layer level, the lower layers are incomplete. This void in the lower layers has favored the growth of the upper layers until a rate of 143% and has accelerated their time appearance. Th incidence energy has favored the filling of lower layers by reducing this surface roughness. However, the temperature effect needs more relaxation time to...