pH changes at near-electrode surfaces

Kuhn, A. T.; Chan, Chee-Yan

doi:10.1007/bf00612481

Cited by 158 publications

(143 citation statements)

References 36 publications

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“…4 At the same time, HCO 3 − /CO 3 2− can chemisorb onto some of the RuO 2 sites to form anion incorporated structurally weak island films. 15 In addition, reactions [5] and [6] can increase the local pH at the electrode surface, 65 and thus can further destabilize/weaken the RuO 2 films by the dissolution reaction:…”

Section: Cmp-specific Surface Modifying Reactions Of Cumentioning

confidence: 99%

Tribo-Electrochemical Characterization of Ru, Ta and Cu CMP Systems Using Percarbonate Based Solutions

Shi

Simpson

Roy

2015

ECS J. Solid State Sci. Technol.

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Defect-control is a critical requirement for chemical mechanical planarization (CMP) of the ultrathin diffusion barriers considered for the new Cu-interconnects. The challenging task of developing advanced CMP slurries for such systems can be aided by electrochemical evaluations of model CMP schemes under tribological conditions. The present work uses this strategy to characterize an alkaline slurry formulation aimed at minimizing galvanic corrosion in the CMP systems involving Ru, Ta (barrier metals) and Cu (wiring metal). This slurry is based on percarbonate and guanidine additives, and the test metals are polycrystalline disc samples. A particular goal of this study is to explore the essential analytical aspects of evaluating CMP systems in the triboelectrochemical approach. The CMP specific surface reactions are characterized by potentiodynamic polarization and open circuit voltage measurements, performed both in the presence and in the absence of polishing, and by employing abrasive free as well as abrasive (colloidal SiO 2 ) added solutions. The findings of these experiments are further checked by using impedance spectroscopy. The electrochemical mixed potential steps of the CMP promoting reactions are analyzed, and the removable surface species formed by these reactions are discussed. The recent developments in the manufacturing of advanced interconnects have largely centered on the Cu/low-k technology, where the processing challenges are coupled with those of material selection. The introduction of mechanically fragile low-k dielectrics has set strict limits on the usable down-pressure of chemical mechanical planarization (CMP) used in the processing of Cu interconnects. This in turn has driven the strategies for material removal more toward the chemical considerations of CMP, and less reliant on mechanical abrasion.2,3 At the same time, the CMP chemistries of the relatively unconventional new barrier materials have presented other challenges, because in the slurry environment, they often have appeared chemically too inert 4 or too corrosive.5 If the CMP chemistries for these new materials are not properly controlled, the processed wafer can develop surface defects due to erosion and galvanic corrosion activated by the wet CMP process. Such defects are detrimental to device performance, and this issue is particularly relevant for the CMP of ultrathin (< 5 nm) barrier films, where defect-control is often more critical than achieving high rates of material removal. Due to these reasons, the tasks of designing the slurry chemistries for metal CMP have become progressively more complex during recent years. This specific aspect of CMP consumable challenges can be addressed to a large extent by employing laboratory scale evaluations of slurry compositions with electrochemical measurements. The present work is based on this approach.The role of electrochemical reactions (and hence the applicability of electro-analytical tests in this context) is integrated in the overall mechanism of chemically promoted metal-C...

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Section: Cmp-specific Surface Modifying Reactions Of Cumentioning

confidence: 99%

Tribo-Electrochemical Characterization of Ru, Ta and Cu CMP Systems Using Percarbonate Based Solutions

Shi

Simpson

Roy

2015

ECS J. Solid State Sci. Technol.

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“…The pH change on the surface of the electrode is a function of many parameters [35]. The most important are the potential or current supplied.…”

Section: The Electrochemical Approachmentioning

confidence: 99%

“…Precipitation of oxides and hydroxides of metals via electrochemical methods is a rapidly developing field [35,36]. A literature survey conducted by Lee and Crayston [37] concluded that electrochemical methods provide simple and cost effective alternatives to methods currently in use.…”

Section: Introductionmentioning

confidence: 99%

Monitoring Heavy Metals in Seawater by Their Electrochemically Induced Deposition as Hydroxides

et al. 2009

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A novel method for monitoring heavy metals in seawater is presented. The method is based on the electrochemical codeposition of metal hydroxides driven by the change of pH at the surface of a gold electrode. Altering the pH is achieved by applying a negative potential or current that reduces the water and thereby increases the concentration of hydroxyl ions. This, in turn, causes metals to coprecipitate with Mg(OH) 2 . The continuous deposition enriches the precipitate with the metals (as compared with their concentration in the aqueous phase) and allows their determination by ICP-MS upon dissolving the deposit. A set of experiments in which seawater was spiked with 1 -10 ppm of Cu, Cr, Co, Zn and Pb, was conducted. It was observed that metals were accumulated in the precipitate as a function of time and their concentration in seawater. The precipitates were analyzed by SEM, EDS and XPS indicating that the metal hydroxides formed a separate phase from Mg(OH) 2 and even water electroreducible metals, e.g., Cu 2þ , preferentially precipitated as hydroxides. Distribution constants correlating the concentrations of the metals in the deposited salts to their concentrations in seawater were calculated. These calculations imply that the mechanism governing the precipitation of the metal hydroxides by the electrochemically induced process is likely to be kinetically and mass-transport driven rather than thermodynamically controlled.

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“…A way to quantify this effect is to measure the pH value close to the electrode surface during electrodeposition, and Kuhn and Chan [7] have summarized various methods. More recently Uhlemann et al [8] have measured the local pH during cobalt deposition.…”

Section: Introductionmentioning

confidence: 99%

Proton Transport during Electrodeposition of Cobalt in Chloride Electrolytes

2011

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In acid cobalt chloride electrolytes the electrodeposition of cobalt and evolution of hydrogen take place simultaneously. On a rotating platinum disc electrode the current efficiency for cobalt deposition was calculated based on the anodic charge needed for stripping of the cobalt deposits divided by the total cathodic charge. The results showed a decrease in current efficiency with increasing rotation rate. From the partial current density for hydrogen evolution the diffusion coefficient for protons was calculated. The derived diffusion coefficients varied with overpotential and pH, but were always one order of magnitude lower compared to what was expected from literature values. This was attributed to water drag when transporting cobalt ions towards the electrode. The variations in the calculated diffusion coefficients were explained by change in the transfer number when the proton concentration was changed.

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pH changes at near-electrode surfaces

Cited by 158 publications

References 36 publications

Tribo-Electrochemical Characterization of Ru, Ta and Cu CMP Systems Using Percarbonate Based Solutions

Tribo-Electrochemical Characterization of Ru, Ta and Cu CMP Systems Using Percarbonate Based Solutions

Monitoring Heavy Metals in Seawater by Their Electrochemically Induced Deposition as Hydroxides

Proton Transport during Electrodeposition of Cobalt in Chloride Electrolytes

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