Dissolution Rate Of Oxide Research Articles

Investigation of deplating behavior of Pt contact pins in semiconductor Cu electroplating process

In wet-contact Cu electroplating processes, the Pt contact pins are deposited with Cu films. In order to maintain the contact quality, the Pt contact pins should be deplated to remove extra Cu films. However, a deplating potential/current that is too large easily causes the water electrolysis reaction to generate micro bubbles, whereas a deplating potential/current that is too small results in inefficient Cu removal. In this study, an electrochemistry analysis system is employed to characterize the behavior of Pt deplating process. It was found that the correlation between deplating efficiency and potential is not linear due to the electric field distribution caused by the electrode resistance. Higher applied potential aggravates the uniformity of electric field distribution so that the effective deplating area decreases. Cu oxides also limit the deplating rate. Based on these results, the dissolution rate of Cu oxides is an important factor in deplating efficiency.

Investigation of AG(I) oxide films by combination of it RRDE and photopotential spectroscopy

AbstractThe RRDE multicycle chronoammetry makes it possible to obtain separately the partial currents of silver ionization, anodic oxide formation, and chemical oxide dissolution. In the range of low anodic potentials (0.48–0.51 V), the process of active silver dissolution from the open parts of the surface and through the pores of oxide film prevails; the phase formation current drops fast. At higher potentials (0.52–0.53 V), the phase formation current prevails and noticeably exceeds the rate of the chemical oxide dissolution. The thickness of Ag2O film rapidly increases; and the net phase formation current is close to 100% during the whole period of polarization. Ag(I) oxide is an n‐type semiconductor with an excess of silver atoms. Their concentration in the oxide film formed on monocrystalline Ag(111), Ag(110), and Ag(100) is less than in the film formed on polycrystalline Ag. Copyright © 2008 John Wiley & Sons, Ltd.

Characterization of the anodic growth and dissolution of oxide films on valve metals

Chemical dissolution processes coupled to anodic oxide growth taking place by a “high-field” conduction mechanism, are considered. The equation for the steady-state current density obtained during potentiodynamic polarization measurements is derived and the effect of the oxide dissolution rate on the overall potentiodynamic behaviour by applying repetitive scans with either fixed or increasing anodic switching potentials is discussed. The procedure for obtaining the current dissolution as well as the parameters that characterize the high-field growth is discussed.

Investigation of the pore formation in anodic aluminium oxide

The mechanism accounting for the self-organization of nanoscale pores during anodic oxidation of aluminium is studied. Microstructural studies support the equifield strength model, which can be used to explain the formation of the hemispherical electrolyte/oxide and oxide/metal interfaces, uniform thickness of the oxide layer, as well as self-adjustment of the pore size and pore ordering. The fundamentals of the model are the electric field enhanced oxide dissolution rate and oxygen anion migration rate. The most important factor for determining the porosity of anodic alumina films with both ordered and disordered pores is the relative dissociation rate of water. The relationships between the porosity and anodization conditions, such as voltage, current density, and electric field strength, are also estimated.

Cathodic processes in the leaching and electrochemistry of covellite in mixed sulfate–chloride media

The cathodic processes that occur on a covellite (CuS) surface in mixed sulfate–chloride solutions in the absence and presence of copper(II) ions have been studied using potentiostatic transients and cyclic voltammetry at rotating disk electrodes in the potential range 0.3–0.7 V (versus SHE). This range is relevant to the oxidative leaching of this copper mineral in sulfate and chloride lixiviants. Variations in the concentrations of sulfate and chloride ions had a small effect on the cathodic reduction of covellite in the potential range of 0.5–0.3 V, although the presence of chloride ion resulted in a significant increase in the anodic current on the reverse sweep. On the other hand, addition of copper(II) ions resulted in enhanced cathodic currents and subsequent anodic currents in both sulfate and chloride solutions due to reduction of covellite to an undefined reduced copper sulfide species. Reduction of copper(II) to copper(I) ions becomes the preferred cathodic reaction as the concentration of chloride ions increases, becoming mass transport controlled at a rotating disc electrode at potentials below about 0.4 V. Potentiostatic measurements at potentials negative to the mixed potential in acidic chloride solutions have shown that reduction of copper(II) ions is reversible and have been used to estimate the rate of oxidative dissolution of the mineral which value agrees reasonably well with previously reported leaching rates under similar conditions. Reduction of dissolved oxygen has been found to be very much slower that that of copper(II) ions under ambient conditions.

Characterization of the influence of fission product doping on the anodic reactivity of uranium dioxide

The influence of fission product doping on the structure, composition, and electrochemical reactivity of uranium dioxide has been studied using X-ray diffractometry (XRD), scanning electron microscopy (SEM/EDX), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Experiments were conducted on SIMFUEL specimens with simulated burn-ups (increasing doping levels) of 1.5, 3.0, and 6.0 atom%. As the dopant level increased, the lattice contracted, suggesting the dominant formation of dopant-oxygen vacancy clusters. The smaller than expected lattice contraction can be attributed to the segregation of Zr (one of eleven added dopants) to ABO3 perovskite-type phases that SEM/EDX shows also contain Ba, Ce, and possibly some U. Raman spectroscopy shows that doping leads to a loss of cubic symmetry, possibly associated with tetragonal distortions. Raman mapping confirms this loss of cubic symmetry and suggests the specimen is not uniformly doped. Electrochemical experiments show that these distortions lead to a decrease in the oxidative dissolution rate of the UO2 with increased doping density.Key words: UO2, X-ray diffraction, electrochemistry, Raman spectroscopy, nuclear fission products.

Multicycle chronoammetry of RRDE in the investigation of the anodic oxide formation

The method of multicycle chronoammetry of RRDE makes it possible to obtain separately the partial currents of metal electrode ionization, anodic oxide formation and chemical oxide dissolution. The method is tested for Ag∣Ag 2O∣OH −(H 2O) system. In the range of low anodic potentials (0.48 ÷ 0.51 V) the process of active silver dissolution prevails; the phase formation current rapidly drops. At higher potentials (0.52 ÷ 0.53 V) the phase formation current prevails and noticeably exceeds the rate of the chemical oxide dissolution. The thickness of Ag 2O film rapidly increases; and the net phase formation current is close to 100%.

A Mathematical Model for the Electrochemical Pickling of Steel

In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is applied. The strip is thereby indirectly polarized, and electrochemical reactions at the strip surface result in the dissolution of the oxide layer and the evolution of hydrogen and oxygen. To obtain a better understanding of this process, we derive in this paper a mathematical model for predicting the potential, current density and ionic species distributions in a vertical pickling cell, as well as the oxide dissolution rate at the steel strip. The model is two dimensional, steady state and isothermal, and is based on the conservation equations for ionic species in dilute solution, involving convection, diffusion, migration and reaction. Kinetic Tafel expressions for the electrochemical gas evolving reactions at the lead anode, stainless steel cathode and at the bipolar steel strip surface are introduced. The derived model comprises six ionic species; numerical solutions for a full version and two reduced versions of this model are then obtained. Finally, the implications of the results for the actual pickling process are discussed.

Cu Post-CMP Displacement Cleaning: A Mechanistic Product Development Approach Based on Selected Thermodynamic and Kinetic Data

ABSTRACTA mechanistic product development approach will be presented that utilized selected thermodynamic and kinetic data for development of a Cu post-CMP cleaner for use after polishing with either high or low pH slurry. A Pourbaix diagram offers the thermodynamically stable Cu species vs. pH and open circuit potential (OCP) for an aqueous cleaner. Pourbaix diagrams do not provide any information on the kinetics for dissolution of water soluble species. Cu oxide dissolution rates were measured using an electrochemical cell. Deposition and removal rates for benzotriazole (BTA) and 1,2,4-triazole (TAZ) were measured using an electrochemical cell with a quartz crystal microbalance (QCM). Passivator film deposition was investigated to determine the film type and thickness resulting from a typical CMP process. BTA and TAZ films deposited near neutral pH were thicker than those deposited at high pH. TAZ films were significantly thinner (∼20Å) than BTA films deposited under similar conditions, approaching a self assembled monolayer (SAM). The BTA removal rate for a citrate solution with a pH of 4 was 20Å/min., an order of magnitude lower than that for TMAH-containing solutions. The TAZ removal rate for an oxalate solution with a pH of 4 was 240Å/min., which was twice the removal rate for BTA deposited under similar conditions. An appropriate TAZ solution was found to displace BTA on Cu and leave a hydrophilic, thin (∼20Å) passivating layer of TAZ. Other Cu passivators were also examined but only TAZ protected all Cu crystallographic orientations observed. BTA, 5-aminotetrazole (5-ATA) and 4-carboxybenzotriazole (CBTA) did not protect some Cu crystal orientations, leading to etching of entire grains and increased surface roughness. BTA and CBTA yielded hydrophobic Cu surfaces, leading to surface wetting issues and the potential for watermarks. A new alkaline Cu post-CMP cleaner was developed to remove residues resulting from slurries, regardless of their pH, which utilizes TAZ to displace BTA and protect Cu, significantly lower organic defects, reduce surface roughness, provide a hydrophilic Cu surface, and significantly extend the staging time allowed between the clean process and subsequent wafer processing.

Residual Waste from Hanford Tanks 241-C-203 and 241-C-204. 1. Solids Characterization

Bulk X-ray diffraction (XRD), synchrotron X-ray microdiffraction (microXRD), and scanning electron microscopy/ energy-dispersive X-ray spectroscopy (SEM/EDS) were used to characterize solids in residual sludge from single-shell underground waste tanks C-203 and C-204 at the U.S. Department of Energy's Hanford Site in southeastern Washington state. Cejkaite [Na4(UO2)(CO3)3] was the dominant crystalline phase in the C-203 and C-204 sludges. This is one of the few occurrences of cejkaite reported in the literature and may be the first documented occurrence of this phase in radioactive wastes from DOE sites. Characterization of residual solids from water leach and selective extraction tests indicates that cejkaite has a high solubility and a rapid rate of dissolution in water at ambient temperature and that these sludges may also contain poorly crystalline Na2U207 [or clarkeite Na[(UO2)O(OH)](H2O)0-1] as well as nitratine (soda niter, NaNO3), goethite [alpha-FeO(OH)], and maghemite (gamma-Fe2O3). Results of the SEM/EDS analyses indicate that the C-204 sludge also contains a solid that lacks crystalline form and is composed of Na, Al, P, O, and possibly C. Other identified solids include Fe oxides that often also contain Cr and Ni and occur as individual particles, coatings on particles, and botryoidal aggregates; a porous-looking material (or an aggregate of submicrometer particles) that typically contain Al, Cr, Fe, Na, Ni, Si, U, P, O, and C; Si oxide (probably quartz); and Na-Al silicate(s). The latter two solids probably represent minerals from the Hanford sediment, which were introduced into the tank during prior sampling campaigns or other tank operation activities. The surfaces of some Fe-oxide particles in residual solids from the water leach and selective extraction tests appear to have preferential dissolution cavities. If these Fe oxides contain contaminants of concern, then the release of these contaminants into infiltrating water would be limited by the dissolution rates of these Fe oxides, which in general have lowto very low solubilities and slow dissolution rates at near neutral to basic pH values under oxic conditions.

Investigation of the mechanism and kinetics of dissolution of nickel(II) and nickel(III) oxides in sulfuric acid

Based on the experimental data on the effect of pH and the H2SO4 concentration on the dissolution rate of nickel oxides, the nature of the limiting stage is revealed, which consists in the formation of surface compounds and their subsequent transfer into the electrolyte solution. The intermediate products of dissolution of nickel(II) oxide in sulfuric acid are identified.

Dissolution of Functional Materials and Rare Earth Oxides into Pseudo Alveolar Fluid

The dissolution rates of rare earth oxides and two types of rare earth containing functional materials into water, saline solution, and Gamble's fluid were measured in order to evaluate the biological effects of rare earth-containing functional materials. The tested materials were yttrium, lanthanum, cerium and neodymium oxides, and neodymium-boron-iron magnet alloy (NdBFe) and lanthanum-mish-metal-nickel-cobalt (LmNiCo) hydrogen-containing alloy. The dissolution rates of the rare earth oxides were very low, resulting in concentrations of rare earth elements in the test solutions of the order of ppb. In the most extreme case, Gamble's fluid dissolved 1,400 times more of the rare earth oxides than pure water. Fairly high concentration of neodymium were found in the dissolving fluids, which means that trace neodymium present as an impurity in each rare earth oxide dissolved preferentially. For yttrium oxide, the ratio of neodymium to yttrium that dissolved in the saline solution was greater than 78,000 to 1, taking into account the amount of each that was originally present in the yttrium oxide.

Organic Acid Mixing to Improve ITO Film Etching in Flat Panel Display Manufacturing

This study examines how oxalic acid mixed with tartaric acid affect indium tin oxide (ITO) etching. When the ITO films were etched with the mixed solutions of oxalic acid and tartaric acid, the dissociation of tartaric acid impeded the formation of oxalate ion and decreased the etching rate of ITO films. Furthermore, the potential–pH diagrams for indium and tin in oxalic acid and tartaric acid systems reveal that indium oxide could be dissolved to form in oxalic acid etchants, and that indium oxide and tin oxide were both soluble in the mixed etchants of oxalic acid and tartaric acid. Additionally, the X-ray photoelectron spectroscopy results demonstrate that the removal rate of was slower than that of in oxalic acid etchants, which induced many residues after the etching process. However, adding tartaric acid to oxalic acid increased the dissolution rate of tin oxide and decreased the level of residues. Consequently, the ITO etching by oxalic acid with tartaric acid shows a more uniform pattern than that by only oxalic acid.

In Vivo Biostability of CVD Silicon Oxide and Silicon Nitride Films

AbstractLow pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD) silicon oxide and silicon nitride films were implanted subcutaneously in a rat model to study in vivo behavior of the films. Silicon chips coated with the films of interest were implanted for up to one year, and film thickness was evaluated by spectrophotometry and sectioning. Dissolution rates were estimated to be 0.33 nm/day for LPCVD silicon nitride, 2.0 nm/day for PECVD silicon nitride, and 3.5 nm/day for PECVD silicon oxide. A similar PECVD silicon oxide dissolution rate was observed on a silicon oxide / silicon nitride / silicon oxide stack that was sectioned by focused ion beam etching. These results provide a biostability reference for designing implantable microfabricated devices that feature exposed ceramic films.

Manganese oxide reactivity in North Sea sediments

Bulk Mn oxide dissolution rates were determined in dilute acid (HCl, pH 3, proton-assisted dissolution) and in saturating ascorbic acid (pH 3, proton-assisted plus reductive dissolution) for North Sea sediments from three sites characterised by different energy regimes, one at the Frisian Front, one in the German Bight, and one in the Skagerrak. Profiles of extractable manganese (0.1 N hydrochloric acid, 1 N hydrochloric acid, citrate-dithionite-bicarbonate buffer and hydroxylamine hydrochloride in acetic acid) are presented for the three sites. The assemblage of sedimentary Mn oxides was described as a reactive continuum with a gamma distribution of Mn oxide reactivities. Initial reduction rates were highest for the oxidised sediment samples. The reactivity of the Mn assemblages during reductive dissolution in ascorbic acid decreased by up to ∼9 orders of magnitude. The largest heterogeneity in Mn reactivity of the oxidised sediment samples was found at the German Bight site, while the most homogeneous Mn assemblage was found at the Skagerrak site. The large range in sedimentary Mn oxide reactivity may explain the great variability in values for kinetic coefficients used to describe Mn reduction. Considering the broad spectrum of Mn oxide reactivities, overlap of the Mn reduction zone with that of Fe oxides is expected.

Magnetic properties of sediment in the Ría de Arousa (Spain): dissolution of iron oxides and formation of iron sulphides

A detailed magnetic study of mineral dissolution has been carried out in order to better characterise the sedimentary environment in the Ría de Arousa, an estuarine-like system in western Spain. There the large number (>3000) of mussel rafts has resulted in a high influx of organic matter causing a change of the original chemical environment. Magnetic measurements of sediment cores (reaching 4.1 m depth) combined with electron microscopy show that there is a distinctive depth trend for the concentration of magnetic minerals. The different iron oxides dissolve with increasing time and depth and at different rates, so that their relative proportions change. At the same time, pyrite is forming, replacing the iron oxides at shallow depths. The magnetic properties of the sediments indicate a high dissolution rate of magnetite (half-life ⩽5 year) and other iron oxides in a strongly reducing environment. Additionally, goethite and hematite in the studied system seem to be less reactive than magnetite.

Influence of initial treatments of aluminium on the morphological features of electrochemically formed alumina membranes

The fabrication of alumina membranes by electrochemical oxidation of annealed aluminium was investigated. Porous layers were grown in 0.4 M H 3PO 4 at −1 and 5 °C at different anodising times. The morphology of the outer surface was found to be dependent on temperature and charge density, with both determining the extent of chemical dissolution of the anodic oxide. The inner-surface morphology was found to depend on the applied voltage only. The chemical dissolution rate of anodic oxide grown on annealed aluminium was found to be lower than that formed on unannealed aluminium under otherwise identical conditions. Such a difference in behaviour is explained in terms of a higher finishing degree of annealed aluminium determining a lower defect concentration in the anodic oxide.

Study of inhibiting effect of acid concentration on the dissolution rate of magnesium oxide during the leaching of dead-burned magnesite

Kinetics of the reaction between dead-burned magnesite and hydrochloric acid were investigated with special regard to the rate of chemical dissolution of MgO. The effect of process parameters viz. temperature, activity of H + ions, and particle size and composition of the solid was investigated. The dissolution of MgO was strongly affected by temperature (from 45 to 75 °C) and particle size (from 63 to 355 μm), while the effect of composition of the solid was weak. The results are presented in terms of the shrinking particle model. The dissolution of MgO is controlled by the chemical reaction of MgO with H + ions at the liquid–solid interface. The apparent activation energy was 58–64 kJ mol −1. Acid concentration (from 1.0 to 5.3 M) was surprisingly found to have a decelerating effect on the dissolution rate of MgO, resulting in negative values of reaction order for H + ions (from −0.1 to −0.2). We conclude that the leaching behaviour studied here corresponds to the regime referred to in the literature as the “initial stage of dissolution of MgO”. This regime, during which the dissolution rate increases rapidly despite a decrease in H + concentration, is characterised by far from mass-transfer control conditions, which was exactly the situation analysed in the present work.

Kinetic dissolution of carbonates and Mn oxides in acidic water: measurement of in situ field rates and reactive transport modeling

The kinetics of carbonate and Mn oxide dissolution under acidic conditions were examined through the in situ exposure of pure phase samples to acidic ground water in Pinal Creek Basin, Arizona. The average long-term calculated in situ dissolution rates for calcite and dolomite were 1.65×10 −7 and 3.64×10 −10 mmol/(cm 2 s), respectively, which were about 3 orders of magnitude slower than rates derived in laboratory experiments by other investigators. Application of both in situ and lab-derived calcite and dolomite dissolution rates to equilibrium reactive transport simulations of a column experiment did not improve the fit to measured outflow chemistry: at the spatial and temporal scales of the column experiment, the use of an equilibrium model adequately simulated carbonate dissolution in the column. Pyrolusite (MnO 2) exposed to acidic ground water for 595 days increased slightly in weight despite thermodynamic conditions that favored dissolution. This result might be related to a recent finding by another investigator that the reductive dissolution of pyrolusite is accompanied by the precipitation of a mixed Mn–Fe oxide species. In PHREEQC reactive transport simulations, the incorporation of Mn kinetics improved the fit between observed and simulated behavior at the column and field scales, although the column-fitted rate for Mn-oxide dissolution was about 4 orders of magnitude greater than the field-fitted rate. Remaining differences between observed and simulated contaminant transport trends at the Pinal Creek site were likely related to factors other than the Mn oxide dissolution rate, such as the concentration of Fe oxide surface sites available for adsorption, the effects of competition among dissolved species for available surface sites, or reactions not included in the model.

Effects of Temperature and Potential on the Passive Corrosion Properties of Alloys C22 and C276

Potentiostatic polarization experiments were performed as a function of potential (200 to 700 and temperature (25-85°C) on the Ni-Cr-Mo alloys C22 and C276. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF SIMS) were used to determine the chemical composition and thickness of the films formed. The currents recorded as a function of applied potential were due to dissolution, with only minor increases in film thicknesses observed. Measured currents for C22 were lower than for C276 and decayed over the entire period of measurement at each temperature. Those on C276 more closely approached steady state. The temperature dependence of the currents on C22 was significantly lower than that on C276. Surface analyses, performed on specimens anodically treated at one potential but after a sequence of temperatures up to 85°C, confirmed that the passive films on both alloys consisted of a Mo, Cr, and Ni oxide, with Cr present as and Mo present in several oxidation states. The passive films on C22 showed a distinct layered structure, consisting of an inner layer rich in Cr and Ni, and an outer layer enhanced in Mo. By contrast, the oxide films on C276 did not show such a clear separation into layers, and the relative Cr content was much lower. The increase in oxide thickness with increasing anodic potential and the low temperature dependence of the passive current observed for C22 are consistent with an oxide dissolution rate which is low compared to the rate of creation of oxygen vacancies leading to film growth. The absence of a dependence of film thickness on potential and the higher temperature dependence of the passive currents on C276 are consistent with control of the overall anodic process by ion-transfer at the oxide/solution interface. © 2003 The Electrochemical Society. All rights reserved.