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An acid-copper plating bath containing chloride ions, polyethylene glycol ͑PEG͒, bis͑3-sulfopropyl͒ disulfide ͑SPS͒, and Janus Green B ͑JGB͒ has been characterized by electrochemical methods and by fill studies on electrode surfaces patterned with trenches ranging in size from 200 to 600 nm, with aspect ratios between 2 and 4. The electrochemical methods employed include linear sweep voltammetry ͑LSV͒, chronoamperometry ͑CA͒, and cyclic voltammetric stripping ͑CVS͒ on a rotating disk electrode. Comparison of the methods shows that in all the cases an analysis of LSV and CA gives consistent estimates of an effective surface coverage of additives. CVS results are consistent with the other results only in baths that are free of JGB. The ability to produce void-free deposits of a bath containing all of the additives can be understood in part with LSV and CA results. However a very good superfilling can also be obtained from a plating bath containing chloride ions, PEG, SPS, but no JGB. This observation cannot be easily interpreted with measurements within the context of established leveling theories.Commercial acid-copper plating baths may contain many organic additives. 1-4 Detailed knowledge of the function of each additive, as well as the interactions between these additives, is lacking despite the advanced state of the technology. The complexity of the bath chemistry, coupled with the incomplete understanding of the mechanisms, makes difficult theoretical predictions of the efficacy of an electrolyte with an arbitrary composition. Industry requires the development of experimental protocols for investigating the influence of composition of perhaps every component of an additive cocktail. The screening method should be fast, reproducible, easy to operate, and with easily interpretable results.We discuss possible screening methods as applied to an acidcopper electrolyte with chloride ions, polyethylene glycol ͑PEG͒, bis͑3-sulfopropyl͒ disulfide ͑SPS͒, and Janus Green B ͑JGB͒. The leveling capability of submicrometer, patterned trenches by this electrolyte has been reported. 1,2 In this paper, we characterize this system by cyclic voltammetric stripping ͑CVS͒, linear sweep voltammetry ͑LSV͒, and chronoamperometry ͑CA͒ studies on a ͑nonpatterned͒ rotating disk electrode ͑RDE͒. Additionally, we investigate the influence of current density, additive composition, and the fluid-flow conditions on the superfilling effect. We show that the LSV and CA methods can sometimes provide a consistent explanation for trench filling experiments; in a companion article in this issue, 5 we show the measurements can be interpreted quantitatively to provide thermodynamic, mass transfer, and kinetic parameters for use in shape-change simulations. ExperimentalFill studies.-The pretreatment of the patterned wafer as well as the deposition procedure is described in Ref. 2. In the present study, copper deposition was carried out under a well-mixed condition, instead of in a stagnant solution. The wafer fragment was placed inside an RDE adapte...

Gas-fed CO2 electrochemical flow reactors are appealing platforms for the electrolytic conversion of CO2 into fuels and chemical feedstocks at commercially relevant current densities (≥100 mA/cm2). An inherent challenge in the development of these reactors is delivering sufficient water to the cathode to sustain the CO2 reduction reaction, while also preventing accumulation of excess water at the porous cathode (i.e., flooding). We present herein experimental evidence showing cathode flooding in a zero-gap electrolyzer at 200 mA/cm2. This flooding causes a 37% decrease in partial current density for CO production (j CO) along with a 450 mV increase in cell voltage (E cell). We show that the detrimental effects associated with this flooding can be mitigated by pairing thin membranes (i.e., ≤40 μm) with hydrophobic cathodes to enable CO2 electrolysis at commercially relevant conditions (j CO ≥ 100 mA/cm2 and E cell < 3 V).

A model describing the effect of an accelerator bis(3-sulfopropyl)disulfide (SPS) and the two inhibitors poly(ethylene glycol) and Janus Green B (PEG and JGB) on the leveling efficacy on submicrometer trenches of an acid-copper plating bath is described, simulated, and compared to experimental fill studies. All parameters of the model are estimated from electrochemical measurements on a nonpatterned, rotating disk electrode. A multicomponent version of a Frumkin isotherm is employed to account for the interaction between SPS and PEG, and the interaction between PEG and JGB are described by a competitive adsorption, Langmuir model. Shape-change simulations employing these descriptions of the surface phenomena are consistent with fill studies over a large range of SPS and JGB concentrations; however, simulations do not predict the result that void-free deposits are achieved when the concentration of JGB is zero. © 2001 The Electrochemical Society. All rights reserved.

Electrochemical reduction of CO2 into carbon-based products using excess clean electricity is a compelling method for producing sustainable fuels while lowering CO2 emissions. Previous electrolytic CO2 reduction studies all involve dioxygen production at the anode, yet this anodic reaction requires a large overpotential and yields a product bearing no economic value. We report here that the cathodic reduction of CO2 to CO can occur in tandem with the anodic oxidation of organic substrates that bear higher economic value than dioxygen. This claim is demonstrated by 3 h of sustained electrolytic conversion of CO2 into CO at a copper–indium cathode with a current density of 3.7 mA cm–2 and Faradaic efficiency of >70%, and the concomitant oxidation of an alcohol at a platinum anode with >75% yield. These results were tested for four alcohols representing different classes of alcohols and demonstrate electrolytic reduction and oxidative chemistry that form higher-valued carbon-based products at both electrodes.