Mechanism Of Copper Electrodeposition Research Articles

Simulation and Experiment of Localized Electrochemical Deposition with Re‐Entrant Structures by Applying the Tip Effect

Re‐entrant structures on the metallic surface play an essential role in the surface properties of materials. However, low efficiency in the preparation of such structures decreases their presence in different application areas. Herein, a new method of localized electrochemical deposition (LECD) manufacturing of re‐entrant structures by applying the tip effect (TE) is introduced. Thanks to this method, manufacturing complex re‐entrant structures can be realized rapidly and efficiently by a simple process without any external control. First, electrochemical measurement methods are used to analyze the copper electrodeposition mechanism, and then a simulation software is adopted to simulate this method. The simulation results suggest that the deposition velocity of the four edges on the copper microcolumn is faster than that of the other position, which means that applying TE makes it feasible to prepare re‐entrant structures by localized electrodeposition. Moreover, experimental results show that the deposition potential of −0.70 V and the deposition time of 900 s are the optimal parameter combinations to obtain the best re‐entrant structures. In addition, the volumetric deposition rate of a single re‐entrant structure can reach 924.8 μm3 s−1. This method provides an opportunity for large‐area manufacturing of re‐entrant structures and lays the foundation for future applications.

An experimental study of copper electroplating by electrochemical impedance spectroscopy (EIS) at room temperature

Electrodeposition of metals, which can be used as catalysts for chemical and electrochemical reactions is a very important process from a practical and technical point of view. Copper is frequently used in electrodeposition technology with applications ranging from undercoat for sequentially plated layers to printed circuit board conductors to electroformed products. The present research is copper electrodeposition mechanism from an acidic sulphate solution that has been investigated by EIS in three potentials i.e., −200, −300 and −400 mV and in a frequency range between 10 mHz and 10 kHz with a constant ac potential. EIS spectra consist of two depressed semicircles with a double layer capacitance. All the EIS spectra proposed one equivalent circuit model (ECM) and the EIS parameters were extracted with the help of ECM. The present work contains information about nucleation and the growth stage of electrodeposition of copper on the graphite. The morphology of the copper deposit changes from spherical to powdery as a function of potentials.

Assessment of the Nucleation and Growth Mechanism of Copper Electrodeposition Over Graphene Oxide

Assessment of the Nucleation and Growth Mechanism of Copper Electrodeposition Over Graphene Oxide

Mechanism analysis of microvia filling based on multiphysics coupling

PurposeCopper electrodeposition acts as a crucial step in the manufacture of high-density interconnect board. The stability of plating solution and the uniformity of copper electrodeposit are the hotspot and difficulty for the research of electrodeposition. Because a large number of factors are included in electrodeposition, experimentally determining all parameters and electrodeposition conditions becomes unmanageable. Therefore, a multiphysics coupling technology was introduced to investigate microvia filling process, and the mechanism of copper electrodeposition was analyzed. The results provide a strong theoretical basis and technical guidance for the actual electroplating experiments. The purpose of this paper is to provide an excellent tool for quickly and cheaply studying the process behavior of copper electrodeposition without actually needing to execute time-consuming and costly experiments.Design/methodology/approachThe interactions among additives used in acidic copper plating solution for microvia filling and the effect on the copper deposition potential were characterized through galvanostatic measurement (GM). The adsorption behavior and surface coverage of additives with various concentrations under different rotating speeds of working electrode were investigated using cyclic voltammetry (CV) measurements. Further, a microvia filling model was constructed using multiphysics coupling technology based on the finite element method.FindingsGM tests showed that accelerator, inhibitor and leveler affected the potential of copper electrodeposition, and bis(3-sulfopropyl) disulfide (SPS), ethylene oxide-propylene oxide (EO/PO) co-polymer, and self-made leveler were the effective additives in acidic copper plating solution. CV tests showed that EO/PO–Cu+-Cl− complex was adsorbed on the electrode surface by intermolecular forces, thus inhibiting copper electrodeposition. Numerical simulation indicated that the process of microvia filling included initial growth period, the outbreak period and the stable growth period, and modeling result was compared with the measured data, and a good agreement was observed.Research limitations/implicationsThe research is still in progress with the development of high-performance computers.Practical implicationsA multiphysics coupling platform is an excellent tool for quickly and cheaply studying the electrodeposited process behaviors under a variety of operating conditions.Social implicationsThe numerical simulation method has laid the foundation for mechanism of copper electrodeposition.Originality/valueBy using multiphysics coupling technology, the authors built a bridge between theoretical and experimental study for microvia filling. This method can help explain the mechanism of copper electrodeposition.

Multiphysics coupling simulation of RDE for PCB manufacturing

Purpose– The purpose of this paper is to optimize experimental parameters and gain further insights into the plating process in the fabrication of high-density interconnections of printed circuit boards (PCBs) by the rotating disc electrode (RDE) model. Via metallization by copper electrodeposition for interconnection of PCBs has become increasingly important. In this metallization technique, copper is directly filled into the vias using special additives. To investigate electrochemical reaction mechanisms of electrodeposition in aqueous solutions, using experiments on an RDE is common practice.Design/methodology/approach– An electrochemical model is presented to describe the kinetics of copper electrodeposition on an RDE, which builds a bridge between the theoretical and experimental study for non-uniform copper electrodeposition in PCB manufacturing. Comsol Multiphysics, a multiphysics simulation platform, is invited to modeling flow field and potential distribution based on a two-dimensional (2D) axisymmetric physical modeling. The flow pattern in the electrolyte is determined by the 2D Navier–Stokes equations. Primary, secondary and tertiary current distributions are performed by the finite element method of multiphysics coupling.Findings– The ion concentration gradient near the cathode and the thickness of the diffusion layer under different rotating velocities are achieved by the finite element method of multiphysics coupling. The calculated concentration and boundary layer thicknesses agree well with those from the theoretical Levich equation. The effect of fluid flow on the current distribution over the electrode surface is also investigated in this model. The results reveal the impact of flow parameters on the current density distribution and thickness of plating layer, which are most concerned in the production of PCBs.Originality/value– By RDE electrochemical model, we build a bridge between the theoretical and experimental study for control of uniformity of plating layer by concentration boundary layer in PCB manufacturing. By means of a multiphysics coupling platform, we can accurately analyze and forecast the characteristic of the entire electrochemical system. These results reveal theoretical connections of current density distribution and plating thickness, with controlled parameters in the plating process to further help us comprehensively understand the mechanism of copper electrodeposition.

Influence of alkylpyridinium ionic liquids on copper electrodeposition from acidic sulfate electrolyte

The effect of two alkylpyridinium ionic liquids (py-iLs) including N-butylpyridinium hydrogen sulfate (BpyHSO4) and N-hexylpyridinium hydrogen sulfate (HpyHSO4) on the kinetics of copper electrodeposition from acidic sulfate solution was investigated by cyclic voltammetry and potentiodynamic polarization measurements. Results from cyclic voltammetry indicate that these py-iLs have a pronounced inhibiting effect on Cu2+ electroreduction and there exists a typical nucleation and growth process. Kinetic parameters such as Tafel slope, transfer coefficient and exchange current density obtained from Tafel plots, lead to the conclusion that py-iLs inhibit the charge transfer by slightly changing the copper electrodeposition mechanism through their adsorption on the cathodic surface. In addition, scanning electron microscope (SEM) and X-ray diffraction analyses reveal that the presence of these additives leads to more leveled and fine-grained cathodic deposits without changing the crystal structure of the electrodeposited copper but strongly affects the crystallographic orientation by significantly inhibiting the growth of (111), (200) and (311) planes.

Study of copper electrodeposition mechanism from a strike alkaline bath prepared with 1-hydroxyethane-1,1-diphosphonic acid through cyclic voltammetry technique

Copper strike baths are extensively used in metal plating industry as they present the ability to plate adherent copper layers on less-noble metal substrates such as steel and zinc die castings. However, in the last few years, due to environmental controls and safety policies for operators, the plating industry has been interested in replacing the toxic cyanide copper strike baths with environmentally friendly baths. A broad bibliographic review showed that the published papers, referring to the new nontoxic copper strike baths, are patents, having little or no emphasis focused on electrodeposition mechanisms. Therefore, it was decided to study the copper electrodeposition mechanism from a strike alkaline bath prepared with one of the most nontoxic chelating agents cited in many patents which is the 1-hydroxyethane-1,1-diphosphonic acid, known as HEDP. This acid forms very stable water soluble complexes with Cu2+ ions, thus cupric sulfate was used for preparing the plating bath. The results obtained through a cyclic voltammetry technique showed that Cu2+ ion reduction to Cu from an HEDP electrodeposition bath occurs via a direct reduction reaction without a formation of Cu+ intermediates.

Electrodeposition of copper from spent Li-ion batteries by electrochemical quartz crystal microbalance and impedance spectroscopy techniques

Information about the copper electrodeposition mechanism at different pH values was obtained using an electrochemical quartz crystal microbalance (EQCM) technique, as well as potentiodynamic, potentiostatic, and electrochemical impedance spectroscopy (EIS) techniques. In agreement with the measurements obtained from the EQCM and potentiostatic experiments, an intermediate Cu+ species and a CuO layer are formed. Simultaneous mechanism of direct reduction of Cu2+ and copper oxide (CuO) reduction at pH 2.0 and 4.5 occur. The EIS experiment shows a diffusion-controlled process by the presence of a Warburg element, a CPE related to the irregular metallic copper electrodeposition, and a resistance of the electrodeposit.

Effects of ionic liquid additive [BMIM]HSO 4 on copper electro-deposition from acidic sulfate electrolyte

The effect of a new ionic liquid additive 1-butyl-3-methylimidazolium hydrogen sulfate-[BMIM]HSO 4 on the kinetics of copper electro-deposition from acidic sulfate solution was investigated by cyclic voltammetry, polarization and electrochemical impedance measurements and compared with those exerted by the conventional additive, thiourea. Results from cyclic voltammetry and kinetic parameters such as Tafel slope, transfer coefficient and exchange current density obtained from Tafel plots, indicated that [BMIM]HSO 4 had a pronounced inhibiting effect on Cu 2+ electro-reduction and led to more leveled and fine-grained cathodic deposits. In addition, [BMIM]HSO 4 was found to inhibit the charge transfer and slightly change the copper electro-deposition mechanism compared to the absence of additives. Data obtained from X-ray diffraction spectra revealed that the presence of these additives did not change the crystal structure of the electro-deposited copper but strongly affected the crystallographic orientation of the crystal planes.

Electroreduction of cupric(II) ions at the ultramicroelectrodes from concentrated electrolytes – Comparison of industrial and laboratory prepared aqueous solutions of copper(II) ions in sulfuric acid electrolytes

The electroreduction of cupric ions has always attracted considerable attention because of its importance for both fundamental and applied aspects. In this paper, the electrodeposition of copper from concentrated real refinery and laboratory prepared electrolytes is investigated. The influence of the complex matrix present in industrial electrolytes (from which active animal glue and thiourea were removed) on the copper electrodeposition mechanism and kinetics was not sufficiently studied in the past. The same can be stated regarding the copper electroreduction investigations in concentrate electrolytes. The influence of potential and temperature on potentiostatic reduction of copper ions at gold ultramicroelectrodes in both electrolytes is studied by chronoamperometric methods. In both studied electrolytes the mechanism of copper nucleation was found to be diffusion controlled, 3D and progressive. The values of apparent bulk diffusion coefficients and the rates of copper nuclei formation in both industrial and synthetic electrolytes are estimated and compared. In both solutions the rate of nucleation increases with absolute value of potential and temperature. Increasing deposit potentials produces smaller nuclei and higher nuclei copper population density. In the whole studied temperatures and potentials ranges AN ∞ changes from 3.30 × 10 9 to 2.50 × 10 13 cm −2 s −2 in industrial and from 1.77 × 10 10 to 1.49 × 10 13 cm −2 s −2 in laboratory prepared electrolytes. The values of diffusion coefficients obtained for industrial and for laboratory prepared solutions do not differ markedly.

Reaction and nucleation mechanisms of copper electrodeposition on disposable pencil graphite electrode

The reaction and nucleation mechanism of copper electrodeposition on disposable pencil graphite electrode (PGE) in acidic sulphate solution were investigated using cyclic voltammetry (CV) and chronoamperometry (CA) techniques, respectively. Electrochemical experiments were followed by morphological studies with scanning electron microscopy (SEM). The effect of some experimental parameters, namely copper concentration, pH, scan rate, background electrolyte, deposition potential, and conditioning surface of the electrode were described. At the surface of PGE, Cu 2+ ions were reduced at −250 mV vs . SCE. It was found that electrodeposition of copper is affected by rough surface of PGE. The nucleation mechanisms were examined by fitting the experimental CA data into Scharifker–Hills nucleation models. The nuclei population densities were also determined by means of two common fitting models developed for three-dimensional nucleation and growth (Scharifker–Mostany and Mirkin–Nilov–Herrman–Tarallo). It was found that deposition potential and background electrolyte affect the distribution of the deposited copper. The morphology of the deposited copper is affected by background electrolyte.

Formation of a Copper Oxide Layer as a Key Step in the Metallic Copper Deposition Mechanism

This paper demonstrates the formation of a Cu(OH)1.5Cl0.5 layer as a key step in the metallic copper electrodeposition mechanism in sulfate solutions. This layer is located surprisingly into the metal/solution interface and not on the reaction substrate. The difficult to study metal/solution interface makes indispensable the use of unconventional measurement techniques. In this way, a careful in situ study by means of acoustic impedance techniques associated with gravimetric techniques allowed the growth of this layer during the metallic copper electrodeposition process to be monitored, probably for the first time.

Advanced Metrology and Control of Copper Electrochemical Deposition I: The Decomposition Chemistry of the Accelerator SPS

Future advances in effective control of the chemical composition of copper electrochemical baths will require an understanding and proactive management of the decomposition products of the additives. To this end, we present the results of mass-spectrometric techniques applied to the identification and quantitation of species that accumulate in Cu-ECD baths by irreversible decomposition of the accelerator bis-(sodium 3- sulfopropyl) disulfide (SPS). Most SPS is converted to 1,3- propanedisulfonic acid (PDS) by way of anodic oxidation via four intermediates, some of which participate in competitive side-reactions that yield alternative decomposition products. A different mechanistic route affords 3-sulfopropan-1-ol as the second most abundant by-product. In this paper we propose several models of SPS decomposition that invoke interfering with the key intermediates in the copper electrodeposition mechanism, and speculate on the role of accelerator break-down products in inducing defects in wafer processing.

Influence of Chloride Anions on the Mechanism of Copper Electrodeposition from Acidic Sulfate Electrolytes

We investigate the influence of chloride ions in a broad range of chloride concentrations on the kinetics and mechanism of copper electrodeposition from sulfate-based acidic electrolytes. Chloride ions influence copper deposition through two competitive effects: at low concentration (few mM), chloride ions depolarize the Cu reduction process, while higher concentrations induce complexation of copper species and cause a cathodic polarization of the deposition process. Cu reduction proceeds through two parallel mechanisms, a direct two-step reduction and a chloride-mediated route, whose relative importance depends on the amount of chloride present. A transition between these two mechanisms can be identified both by steady-state and impedance methods; however, the chloride concentration at which it occurs depends on the time scale probed by the two techniques. Impedance measurements further demonstrate that the presence of chlorides changes the double-layer structure.

Mechanism of copper electrodeposition in the presence of picolinic acid

The influence of picolinic acid (PA) on copper deposition from a slightly acidic sodium sulphate electrolyte has been studied over a wide range of concentration and pH by cyclic voltammetry. The mechanism by which the copper electrodeposition process in the presence of PA takes place, depends on the chemistry and electrochemistry characteristics of the additive. Depending on the PA concentration and pH of the solution, five different cathodic current peaks are obtained, which are assigned to different steps involving copper deposition from free-Cu 2+ ions and [Cu(PA) n ] 2+ complex species as well as H + ions electroeduction. Fine-grained, highly adherent and bright copper deposits were obtained.

Electrodeposition of monodisperse copper nanoparticles on highly oriented pyrolytic graphite electrode with modulation potential method

Copper nanoparticles with size of 51 nm and R.S.D. dia of 10% can be obtained by modulation potential electrodeposition: first, a −0.8 V × 120 ms potential step was used to nucleate copper particles on highly oriented pyrolytic graphite (HOPG) electrode surface, where nuclei with a supercritical size were formed, secondly, a 0.082 V × 80 ms strip peak potential ( E s) was used to strip smaller metal nuclei partly, at last, a growth potential, −0.28 V was applied to grow the nearly identical size slowly. Mechanism of copper electrodeposition on HOPG electrode from a solution of 1 mM CuSO 4 and 1.0 M H 2SO 4 has been studied using cyclic voltammogram and chronoamperometry. In copper electrodeposition the charge-transfer step is fast and the rate of growth is controlled by the rate of mass transfer of copper ions to the growing centers. Reduction of Cu(II) ions did not undergo underpotential deposition. The initial deposition kinetics of Cu electrocrystallization corresponds to a model including progressive nucleation and diffusion controlled growth.

Copper electrodeposition from sulfate electrolytes in the presence of hydroxyethylated 2-butyne-1, 4-diol

Data has been obtained on the levelling effect of hydroxyethylated-2-butyne-1, 4-diol (“Ferasine”) in the copper electrodeposition from acidic sulfate electrolytes using cyclic voltammetry, hydrodynamic quasi steady-state voltammetry at rotating disc electrodes (RDE) and electrochemical impedance measurements. These are corroborated with morphological and structural analysis of copper deposits leading to the conclusion that finer grained deposits are produced, promoting a [110] texture. The additive moderately hinders the mass transfer of the copper ions from the bulk solution to the outer limit of the electrode double layer. Due to its adsorption on the electrode surface, Ferasine inhibits the charge transfer and slightly changes the copper electrodeposition mechanism. It affects the electrocrystallization step, impeding the crystal growth process and promoting the nucleation of copper.

Influence of additives on Cu electrodeposition mechanisms in acid solution: direct current study supported by non-electrochemical measurements

The effect of polyethylene glycol (PEG) and chloride ions on copper electrodeposits is investigated by electrochemical measurements (cyclic voltammetry, current and potential pulses) coupled with an ellipsometric study at open circuit. When PEG is added to the Cu 2+ solution, the modifications of the copper electrodeposition mechanism can be explained by a polymer-electrode interaction instead of a complex formation in solution. Since ellipsometry has shown no PEG adsorption at least at open circuit, that adsorption is assumed to be potential dependent. Moreover, the efficiency of PEG alone in solution, seems to be decreased when the deposit grows. With Cl − alone, an activation of copper deposition is performed. The simultaneous addition of the two additives induces a blocking effect of the copper reduction that continues on with time. X-ray diffraction, optical microscopy and atomic force microscopy (AFM) carried out complementary results, on bulk deposits obtained from solution with and without these additives. It has been found that a bright, compact and homogeneous coating is only obtained in presence of both additives. In that case, the texture of the deposit is modified and the roughness is significantly decreased to 0.5 μm.

Monte Carlo Simulation of the Electrodeposition of Copper : II. Acid Sulfate Solution with Blocking Additive

Simulation of copper electrodeposition in the presence of a hypothetical blocking additive was carried out by a linked continuum/noncontinuum numerical code for various geometric configurations in the shape of a rectangular trench. The mechanism of copper electrodeposition described in Part I of this series was extended to include a single additive species. The hypothetical additive had the property that it blocks deposition but is consumed at the surface, and that its arrival at the electrode surface is transport-limited so that leveling occurs. With use of numerical simulations carried out with a linked Monte Carlo-finite difference code described in Part I, the effect on trench in-fill of additive concentration, adsorption rate, consumption (breakdown) rate, and trench aspect ratio was investigated. © 2002 The Electrochemical Society. All rights reserved.

Mechanism of copper electrodeposition by pulse current and its relation to current efficiency

The effects of pulse periods and duty cycles on the current efficiency of acid copper plating in a wide range of pulse periods from 200 to 0.02 ms were studied. It was found the current efficiency decreased with shortening pulses in the millisecond range but increased with shortening pulses in the microsecond range. A mathematical model based on the concept of equivalent circuit was employed to simulate the potential responses. Shortening the pulse period was found to change the rate-determining step from charge transfer and surface diffusion to the first step charge transfer. In the millisecond range, the current efficiency decreases with shortening pulse period due to the disproportionation of cuprous ions and the dissolution of copper adatom. However, in the microsecond range, the current efficiency was found to increase with decreasing pulse period because the adatoms are directly incorporated into steps and kink sites, and the disproportionation of cuprous ions or the dissolution of copper adatoms has less chance to occur.