Bath Constituents Research Articles

A new design strategy for the crack-free composite CaHPO4·2H2O/CaCO3 coating on AZ41 Mg alloy for magnesium concrete formwork

To address the limited corrosion resistance of magnesium alloys, calcium phosphorus coatings are frequently applied to their surfaces as a means of compensating for this drawback. However, cracking of traditional calcium phosphorus coatings greatly affects their protective properties. In this research, a novel CaHPO4·2H2O (DCPD) and CaCO3 composite coating with no cracks was obtained via a chemical conversion method assisted by ultrasound. DCPD coatings were also fabricated in the same method. All the coatings possess excellent adhesion strength to the substrates. In addition, electrochemical tests results show that the elimination of cracks greatly improves the anticorrosion performance of composite coatings. Optimization of the bath constituents resulted in a reduced reliance on interfacial electrochemical reactions during the co-deposition process, which plays a critical role in attaining the high-quality coating. This innovative composite coating provides a promising avenue for surface treatments of magnesium alloy concrete formwork.

Damped Oscillators within the General Theory of Casimir and van der Waals Forces

It is demonstrated that the general theory of Casimir and van der Waals forces describes the interaction-induced equilibrium thermodynamic potentials of the damped harmonic oscillator bilinearly coupled to the environment. An extended model for a damped oscillator is suggested along the lines of the general theory of Casimir and van der Waals forces, and the corresponding thermodynamic quantities obtained. While the original model involves a heat bath consisting of a large number of free oscillators having infinitesimal damping functions, the extended model allows any generally admissible frequency and temperature dependent dissipative susceptibilities of the heat bath constituents, influenced by the additional dissipative environmental channels that are not directly linked to the system oscillator. Consequently, the results obtained are applicable to the frequency and temperature dependent damping function of the system oscillator.

Electrochemical Deposition and Spectroscopy Investigation of Zn Coatings on Steel

A three-electrode electrochemical cell was used for the optimization of bath constituents and parameters. Galvanostatic electrodeposition from a free additives bath, combining sulfate and chloride compounds results in bright Zn deposits with high corrosion resistance. Surface morphology was observed by scanning electron microscopy, chemical and phase composition were determined by X-ray diffraction, and corrosion investigations by electrochemical techniques. Electrochemical impedance spectroscopy (EIS) and polarization measurements revealed that the electrodeposited Zn coating with the higher current density and pH value had the best corrosion resistance. Bright and uniform surface appearance, of Zn deposits, with a platelet structure, moderate current efficiency and a high corrosion resistance was obtained at a pH of 4.5 and a current density of 16 mA cm−2.

Electrodeposition of Zn–Ni Monolithic Coatings, Characterization, and Corrosion Analysis

Bright Zn–Ni coatings were developed by using thiamine hydrochloride as a brightener. Hull cell was used for the optimization of bath constituents and parameters. Galvanostatic electrodeposition from zinc sulfate and nickel sulfate with additives results in Zn-rich solid solution of nickel in zinc η-phase. Surface morphology was observed by scanning electron microscopy, chemical and phase composition determined by X-ray diffraction, and corrosion investigations by electrochemical techniques. Coatings obtained at 5 Adm−2 exhibited more corrosion resistance.

Studies on electrodeposited Zn-Fe alloy coating on mild steel and its characterization

Chloride bath containing ZnCl2 ∙7H2O, FeCl2 ∙H2O and a combination of sulphamic acid and citric acid (SA+CA) were optimized for electrodeposition of bright Zn-Fe alloy coating on the mild steel. Bath constituents and operating parameters were optimized by the Hull cell method for highest performance of the coating against corrosion. The effect of current density and temperature on deposit characteristics such as corrosion resistance, hardness, thickness, cathode current efficiency and glossiness, were studied. Potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) methods were used to assess corrosion behaviour. Surface morphology of coatings was examined using scanning electron microscopy (SEM). The Zn-Fe alloy with intense peaks corresponding to Zn (100) and Zn (101) phases, evidenced by X-ray diffraction (XRD) study, showed the highest corrosion resistance. A new and economical chloride bath for electrodeposition of bright Zn-Fe alloy coating on mild steel was proposed and discussed.

Temperature Compensation by Embedded Temperature Variation Method for an AC Voltammeric Analyzer of Electroplating Baths

AbstractAn in‐situ sensor utilizing a variety of DC‐ and AC‐voltammetric techniques is an integral component of the on‐line monitoring system that provides a complete chemical analysis of different plating solutions by predicting concentration values of all deliberately‐added bath constituents with a single device despite differences in the constituents’ chemical properties. Such sensors are employed routinely for electroplating process control in semiconductor manufacturing. This voltammetric approach exploits quantitatively the physicochemical processes (like adsorption) which are temperature dependent. Therefore the accuracy of analyte concentration predictions can be affected adversely by temperature fluctuations. This paper introduces a novel comprehensive method which allows the mitigation of temperature variation effects on voltammetric scans allowing accurate concentration prediction. Specifically, this study introduces a multi‐step rigorous routine for the development and subsequent validation of the analytical method utilizing a chemometric model with temperature variation embedded in regression for exemplary determination of leveler additive concentration. This approach analyses the effect on AC voltammograms resulting from two qualitatively indistinguishable sources of variation: leveler concentration and temperature. A critical step of this routine of fundamental novelty, which aims to select the variables (index points of voltammogram) to be utilized for building of the analytical model in the presence of two concurrent sources of variation, is introduced to incorporate temperature variation.

(Invited) Additives in Cu Plating for Microelectronics Applications

Electrodeposition is a prevailing method in fabrication of Cu interconnects in microelectronics due to its ability to fill complex structures having a wide range of critical dimensions. A typical acidified Cu electrolyte contains a number of additives, organic and inorganic species in ppm amounts, with a specific role in the plating process. The additives in Cu plating have been extensively studied in the past couple of decades, and grouped according to their role in filling/creating features for microelectronics applications. This categorization is not a uniform one, and it might differ from author to author. In one popular convention, organic additives in the so-called three-component plating bath are named accelerator, suppressor and leveler, with their names hinting at how they influence Cu deposition. Ultimately, it is thanks to these additives that defect-free Cu features ranging from tens of nanometers to hundreds of micrometers can be economically fabricated. However, it is not enough to successfully fill a given single feature. The same has to be done for all the features on a 300 mm wafer, and then performed reproducibly over and over again. So, one needs to monitor the state of the electrolyte, i.e. of all the bath constituents, and either replace or replenish the electrolyte when the need arises. Additives could also have a strong influence on the physical properties of the deposit and therefore have a strong influence on the post-plating processing results. An additive that promotes void-free deposition of Cu structures in the end might not be used in a production line if it creates issues in the processing steps following electrodeposition. In our presentation we focus on a number of specific examples showing the effect of additives on nucleation and growth of Cu, propagation of Cu fronts on resistive substrates, post-plating processing, and their use in substrate surface modifications. A closer look is taken into in situ microscopic and electrochemical techniques and their use in studies of electrochemical nucleation and growth of Cu. We discuss advantages and drawbacks of potential step and galvanostatic deposition techniques in determining nucleation and growth parameters, and selection criteria for additive sets for a given plating task. We demonstrate that substrate surface modifications prior to plating could help simplify bath composition, i.e. eliminate need for some additives in the electrolyte, or improve the filling performance of the given plating bath. We also give examples of additives that promoted void-free filling of features but also influenced physical/mechanical properties of the final product in such a way that rendered it unusable in a specific application.

Temperature Compensation by Calibration Transfer for an AC Voltammetric Analyzer of Electroplating Baths

AbstractThe application of methods for mitigating the effects of temperature fluctuations on the analytical performance of an in‐situ DC‐ and AC‐voltammetric sensor employed for electroplating process control in semiconductor manufacturing is presented. This sensor is a part of an automated analytical system capable of predicting concentration values of deliberately‐added bath constituents based on the component‐specific multivariate voltammetric responses. However, these responses include physicochemical phenomena, some of which are strongly dependent on temperature; therefore temperature fluctuations can produce an additional source of variance in the voltammetric responses adversely affecting the accuracy of analyte concentration predictions. Several calibration‐transfer‐based techniques, both discrete and continuous, using Piecewise Direct Standardization and Direct Standardization combined with PCR and PLS analytical models are comparatively validated for temperature compensation using AC voltammetric data for the example of accelerator additive. An extension of implementation of continuous methods for Direct Standardization is proposed along with an introduction of a new hybrid method of Standardization Models.

Induced codeposition of Ni-W alloy coatings using glycerol as additive and their characterization

As a promising coating material to replace hard chromium coating, the development of nickel–tungsten (Ni-W) alloy coatings of good corrosion protection is of great interest in surface coating technology. Further, the effect of plating variables, including additive on the composition of alloys of induced co-deposition is more vagarious than in other types of alloy deposition. In this regard, an alkaline citrate bath has been formulated for electrodeposition of Ni-W alloy through conventional Hull cell method, using glycerol as additive. Electrodeposition following the induced type of codeposition of Ni–W alloy was carried out onto mild steel (MS) substrate at different current densities (c.d.’s) at room temperature, taking a basic bath. Influence of bath constituents and operating parameters on the appearance, hardness, thickness and composition of the deposits were studied as a measure of their performance against corrosion. Corrosion behaviours of Ni-W coatings, having hard-adherent mirror bright appearance were studied using Tafel’s polarization and electrochemical impedance spectroscopy (EIS) method in 5 wt. % NaCl solution. Experimental results revealed that corrosion protection efficacy of Ni-W coatings increased with deposition c.d., in proportion of its W content. The coating developed at 4.0 A dm-2 was found to exhibit the least corrosion rate (5.3 x 10-2 mm y-1), compared to those at other c.d.’s. The process and product of electrodeposition have been studied using different instrumental methods, such as Cyclic voltammetry (CV), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) study. Experimental observations were analyzed in the light of induced codeposition of Ni-W alloy due to stimulation by Ni+2 ions, and results are discussed.

ELECTRODEPOSITION OF ZINC-NICKEL ALLOY IN THE PRESENCE OF LAWSONE ISOLATED FROM LAWSONIA INERMIS LINN LEAF

The electro deposition of zinc-nickel alloy was carried out in the presence of Lawsone (2-hydroxy1,4-napthoquinone) isolated from Lawsonia inermis Linn leaf. The bath constituents were optimized through Hull cell experiments. Operating parameters such as pH, temperature and current density were also optimized. The current efficiency and throwing power are measured at different current densities.SEM photomicrographs revealed fine-grained structure of the deposit from the optimum bath. IR spectrum of the scratched deposit showed inclusion of addition agent. XRD and EDAX studies revealed the inclusion of lawsone.

Case Study of Early Detection of Iron Contamination in Copper Damascene Plating Process by In-Situ Electrochemical Sensor

A case of detection of iron contamination of the plating solution used in semiconductor manufacturing by a system for plating bath process control utilizing a novel approach that combines advanced electroanalytical methods with various statistical data analysis techniques based on chemometric factor analysis is described. Retrospective research aiming to determine the iron contamination level is presented. The electroanalytical techniques employed, including DC- and AC-voltammetry, are designed to provide a response strongly affected by the presence of specific contaminants while being practically insensitive to the varying concentrations of deliberately added bath constituents. The shape differences between deformed and training set voltammograms are quantified using various outlier-detection chemometric techniques. The specificity of the response to the presence of a likely contaminant combined with multi-parameter quantification of its presence enables not only early-fault detection but also its diagnosis, therefore automating the troubleshooting process.

Case Study of Early Detection of Iron Contamination in Copper Damascene Plating Process by In-Situ Electrochemical Sensor

Copper electrochemical deposition (ECD) is utilized in various fields of advance manufacturing ranging from complex multilayer flex and rigid printed circuit boards (PCB), to semiconductor copper plating including damascene and through-silicon vias (TSV) processes for the production of ULSI circuits. Monitoring of only the deliberately added bath constituents concentrations does not guarantee satisfactory performance of the plating solution. Prompt detection and diagnosis of disturbances leading to an out-of-control process behavior is critical for reducing losses in process operations. As ECD processes, like many chemical processes, are becoming more measurement-rich, conventional univariate process control methods become inadequate. Chemometric techniques have been applied to process problems (as opposed to analytical chemistry). These applications can be roughly divided between those directed at maintenance of process instruments, e.g., calibration and its transfer, and those that are concerned with the maintenance of the process itself, e.g., statistical process control (SPC) and fault detection. A system was developed utilizing a novel approach that combines electroanalytical methods including DC- and AC-voltammetry with various chemometric techniques using the same hardware for both applications of chemometrics: calibration and SPC. The focus of this presentation is on the latter area, specifically on statistical discriminant data analysis techniques based on chemometric factor analysis. All measurements and calculations were performed using instrumentation and software custom-developed for this application.The electroanalytical techniques employed were designed to provide a response strongly affected by the presence of foreign contaminants [1,2], accumulated degradation products, out-of-target concentrations of bath constituents and out-of-target physical conditions of the plating process (i.e. temperature). A modeling-power [1] based condition was defined and implemented to determine which portion of the voltammetric response can be effectively decomposed by factor analysis prior to discriminant analysis. The shape differences between deformed and training set voltammograms were quantified using various outlier-detection chemometric techniques including PCA [1], MD/PCA, MD/PCA/R [1], SIMCA and Fs-ratio [1].The effectiveness of the system was proven by detection of foreign contamination with iron in a copper damascene bath caused by unnoticed dropping of the carbon steel chapman bit into the plating chamber while changing the anode in between of high-volume production runs. Thanks to the prompt warning, significant production losses were prevented.This presentation focuses also on retrospective study leading to a development of an analytical model capable not only of detection but also of diagnosis of the specific type of contamination.A. Jaworski, H. Wikiel, K. Wikiel, ECS Trans. 25 (3), 199 (2009).A. Jaworski, H. Wikiel, K. Wikiel, Electroanalysis, 23 (1), 253 (2011).

Multilayer Zn-Ni-Al<SUB align="right">2O<SUB align="right">3 coatings for corrosion protection

The paper reports the development of composite coatings of Zn-Ni-Al2O3 by composition modulated multilayer (CMM) technique using m-aminophenol and gelatin as additives. The bath constituents and deposition parameters were optimised by conventional method. The role of gelatin and m-aminophenol in the bath was analysed by cyclic voltammetry (CV) study. Corrosion performance of the monolayer coatings was enhanced further by multilayer technique. The modulation in composition was effected by pulsing the DC in square-wave patterns. The coatings configurations were optimised for peak performance of the coatings against corrosion. It was found that corrosion resistance of CMM coatings increased with number of layers up to certain optimal numbers, and then decreased. Incorporation of Al2O3 particles into metal matrix was confirmed by EDAX. Formation of layered coating and their phase structures were analysed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) study. Reasons responsible for better corrosion resistance of CMM composite coatings are analysed and results are discussed.

The dynamical role of initial correlation in the exactly solvable dephasing model

We investigate the effects of the initial correlation on the dynamics of open system in the exactly solvable pure dephasing model. We show that the role of the initial correlation come into play through a phase function and a weight factor, which would perform oscillations during time evolution, and find that the decoherence of a qubit coupled to a boson bath is more enhanced with respect to a spin bath in the short time. We also demonstrate that the trace distance between two states of a qubit can increase above its initial value, and that the initial correlation can provide another resource for the damply oscillation and revival of the entanglement of two qubits. We finally investigate the dependence of the crossover of decoherence from the dynamical enhancement to suppression under the bang-bang pulse control on the initial correlation and the statistics of the bath constituents.

Automated AC Voltammetric Sensor for Early Fault Detection and Diagnosis in Monitoring of Electroplating Processes

AbstractAn in situ sensor employing AC‐voltammetry techniques was designed to provide a response strongly affected by the presence of specific disturbances like foreign contaminants, accumulated degradation products, severely out‐of‐target concentrations of electroplating bath constituents and out‐of‐target physical conditions of the plating process (i.e. temperature). Soft Independent Modelling of Class Analogy (SIMCA) is a pattern recognition method which describes each class separately in eigenvector space. In this supervised classification technique the projected new measurements are evaluated to determine whether they belong to a certain class or not. An automated analytical system was developed capable of collecting on‐line AC voltammetric data and investigating similarities between measurements in proper conditions and measurements with upset behavior with known disturbances which can be utilized to recognize a likely pattern of behavior. The shape differences between deformed and reference set voltammograms are quantified by Mahalanobis Distance (MD)‐SIMCA. In addition to the numerical approach, a graphical projection is utilized to diagnose the root cause of the detected process disturbances.

Molecular vibrations-induced quantum beats in two-dimensional electronic spectroscopy

Quantum beats in nonlinear spectroscopy of molecular aggregates are often attributed to electronic phenomena of excitonic systems, while nuclear degrees of freedom are commonly included into models as overdamped oscillations of bath constituents responsible for dephasing. However, molecular systems are coupled to various high-frequency molecular vibrations, which can cause the spectral beats hardly distinguishable from those created by purely electronic coherences. Models containing damped, undamped, and overdamped vibrational modes coupled to an electronic molecular transition are discussed in this paper in context of linear absorption and two-dimensional electronic spectroscopy. Analysis of different types of bath models demonstrates how do vibrations map onto two-dimensional spectra and how the damping strength of the coherent vibrational modes can be resolved from spectroscopic signals.

NEW BRIGHTENER FOR Zn-Ni ALLOY PLATING FROM SULFATE BATH

Zinc-nickel alloy electrodeposition was carried out in the presence of the condensation product formed between chitosan and vanillin in an acid sulfate bath. A Hull cell was used for optimizing the operating parameters and bath constituents. During deposition, the potential was shifted towards the cathodic direction in the presence of addition agents. Current efficiency and throwing power under different experimental conditions were measured. SEM images of the bright deposit indicated its fine-grained nature and appreciable reduction in grain size. Corrosion studies revealed the protective properties of the alloy coating.

Unusual "chemical" mechanism of carbon co-deposition in Cr-C alloy electrodeposition process from trivalent chromium bath

Kinetics and mechanism of chromium-carbon alloy deposition process were investigated using trivalent chromium electroplating bath containing formic acid and carbamide (urea). The rate of carbon co-deposition process is determined by the rate of chromium electroplating reaction (electrochemical process of Cr-deposition imposes its own kinetics regularities on carbon co-deposition). It was supposed that a part of active chromium ad-atoms generated as a result of Cr(II) ions discharge may interact with adsorbed organic bath constituents by "chemical" mechanism.

Flat Absorber Phosphorous Black Nickel Coatings for Space Applications

A new process of flat absorber black nickel alloy coating was developed on stainless steel by electrodeposition from a bath containing nickel, zinc and ammonium sulphates; thiocyanate and sodium hypophosphite for space applications. Coating process was optimized by investigating the effects of plating parameters, viz concentration of bath constituents, current density, temperature, pH and plating time on the optical properties of the black deposits. Energy dispersive X-ray spectroscopy showed the inclusion of about 6% phosphorous in the coating. The scanning electron microscopy studies revealed the amorphous nature of the coating. The corrosion resistance of the coatings was evaluated by the electrochemical impedance spectroscopy (EIS) and linear polarization (LP) techniques. The results revealed that, phosphorous addition confers better corrosion resistance in comparison to conventional black nickel coatings. The black nickel coating obtained from hypophosphite bath provides high solar absorptance (αs) and infrared emittance (ɛIR) of the order of 0.93. Environmental stability to space applications was established by the humidity and thermal cycling tests.

Optimization of deposition conditions for bright Zn-Fe coatings and its characterization

Sulfate bath having ZnSO4 · 7H2O, Fe2(SO4)3 · H2O and thiamine hydrochloride (THC) and citric acid (CA) in combination, represented as (THC + CA) was optimized for deposition of bright Zn-Fe alloy coating on mild steel. Bath constituents and operating parameters were optimized by standard Hull cell method, for peak performance of the coating against corrosion. The effect of current density (c.d.), pH and temperature on deposit characters, such as corrosion resistance, hardness and glossiness were studied and discussed. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion behaviors. Surface morphology, and composition of the coatings were examined using Scanning Electron Microscopy (SEM), interfaced with EDXA facility, respectively. The Zn-Fe alloy, with intense peaks corresponding to Zn(100) and Zn(101) phases, showed highest corrosion resistance, evidenced by X-ray diffraction (XRD) study. A new and cheap sulfate bath, for bright Zn-Fe alloy coating on mild steel has been proposed, and results are discussed.