Search

Through-glass vias (TGVs) have been extensively researched due to the unique properties of glass, including low dielectric constant, high transparency, high mechanical, thermal and chemical resistance, and low cost. The TGVs are typically filled with Cu by electrodeposition to make electrical connections in high-performance electronics with 3D integration. The Cu electrodeposition process employed to fill the through-holes is similar to the one used for printed circuit boards (PCBs), and defect-free Cu can be achieved with a butterfly filling mechanism. This study introduces the defect-free Cu filling of TGVs using polyvinylpyrrolidone (PVP) as a leveler. The effects of PVP molecular weight on the formation of suppression layers on the Cu surface was examined by electrochemical analyses. It was found that the smaller PVP (10,000 g/mol) was beneficial, forming a more compact suppression layer. In contrast, the layer of larger PVPs (360,000 g/mol) contained a large number of defects where the accelerator could adsorb, resulting in conformal electrodeposition. As a result, the PVP with a molecular weight of 10,000 g/mol led to defect-free butterfly filling at TGVs with increasing the filling performance by 20% compared to the larger PVP.

In this study, the composition-optimized Pd–Cu catalyst for electrochemical N2O reduction in highly alkaline solution was prepared by a galvanic displacement method. The atomic ratio of Pd to Cu in Pd–Cu bimetallic catalyst, which has been known to be hardly controlled using galvanic displacement, was tailored by varying the concentration of citric acid in galvanic displacement bath. With increasing citric acid concentration, the decreased grain size, characterized by X-ray diffraction, and the increased amount of carbon in Pd–Cu catalyst, measured by energy-dispersive X-ray spectrometry, revealed the incorporation of citric acid into the catalyst, which was attributed to the tunable catalyst composition. The incorporation of citric acid into Pd–Cu deposit restrained the diffusion of Cu from Cu substrate to deposit, leading to decrease in the Cu content in Pd–Cu. The electrocatalytic activity for N2O reduction was strongly dependent on the Pd/Cu composition in Pd–Cu catalysts. Among the investigated Pd–Cu catalysts with different compositions, the highest electrocatalytic activity was obtained with Pd60Cu40 with a Tafel slope of 0.096 V dec−1. Moreover, the Pd60Cu40 catalyst showed remarkably enhanced mass-specific activity for N2O reduction, compared with a commercial Pd/C. The density functional theory (DFT) calculations revealed that the highest N2O reduction activity of Pd60Cu40 could be attributed to the facilitation of an adsorption/desorption balance for N2O reduction, resulting from the appropriately lowered d-band center of catalyst.

Herein, we fabricate heterostructured copper oxide nanowires decorated with amorphous Sn by Cu anodization and Sn electrodeposition for a potential application as anode in Li-ion battery. In general, Sn experiences a pulverization caused by the stress from a severe volume change during the reaction with Li-ion. Therefore, the stress should be certainly mitigated. A nanowire with 1-D structure could be a candidate anode material because it accommodates the volume change and enlarges the surface area of electrode. Yet Sn nanowire still suffers the harsh stress, copper oxide is employed as an active anode material as well as a structural framework in the present study. By virtue of the Li-conversion mechanism of copper oxide, the as-prepared Sn-decorated copper oxide nanowire exhibits an improved discharge capacity and maintains it as high as 633.0 mAh g−1 at extended cycles (77.7% of initial capacity at 150th cycle). From a rate capability experiment, the nanowire electrode presents the capacity of 424 mAh g−1 at 16 C, and shows a moderate recovering ability. The 1-D heterogeneous structure and Cu nodes that are intentionally formed during electrochemical fabrication helps realizing a cell configuration without a binder and a conducting agent, which ultimately contributes to increase energy and power density of Li-ion battery.

Through silicon via (TSV) is one of the most important technologies in 3-dimensional wafer/chip stacking. However, there are some issues related to defect-free TSV filling and Cu pumping. In this study, a defect-free TSV filling was achieved using iodide ions. The working mechanism of iodide ions in TSV filling was systemically investigated by electrochemical measurements; It was found that the formation of CuI on the electrode surface is a key process for inhibiting Cu ion reduction. This inhibition effect of iodide ions enables defect-free TSV filling. Furthermore, the study of microstructure of the filled Cu revealed that the electrochemical reduction of CuI during the TSV filling forms small Cu grains in TSV. The small Cu grains cause Cu pumping in subsequent processes, which damages semiconductor devices. We achieved a defect-free TSV filling with enlarged Cu grains using a two-step filling method that effectively promotes the direct reduction of Cu ions rather than electrochemical reduction of CuI.

Electrodeposition of Cu-based alloys has been researched for a variety of applications due to Cu-based alloys having superior properties compared to pure Cu, including higher chemical resistance, mechanical hardness, and electrocatalytic activity. Cu-Ag is the most electrically conductive among Cu-based alloys, and it has higher mechanical hardness and oxidation resistance compared to pure Cu. Cu-Ag co-deposition in cyanide-based electrolytes has been previously reported; however, the toxicity of cyanide limited its use. In this study, we introduce an ammonium hydroxide-based electrolyte for Cu-Ag electrodeposition and the properties of Cu-Ag films deposited in this electrolyte. Electrochemical measurements were performed to determine the potential range for co-electrodeposition of Cu and Ag, and the effect of nitrate reduction on the film deposition was examined. The effects of deposition potential and concentration of Ag ions in the electrolytes on the electrical resistivity and Ag contents of the films were investigated. The modulation of Ag ion concentration was found to be a more effective way to control Ag contents in the deposited films. Co-deposition of 4 at% Ag with Cu in the ammonium-hydroxide electrolyte markedly improved mechanical hardness and oxidation resistance compared to a pure Cu film without severe deterioration of electrical conductivity.

The activity of electrocatalysts can be improved by modifying their electronic structures and surface morphologies. In electrochemical reactions with gas evolution, the performance of an electrocatalyst is also affected by how easily gas bubbles depart from an electrocatalyst surface. However, it is difficult to quantitatively estimate the improvement in the performance that can be achieved by promoting the departure of gas bubbles from the electrocatalyst surface. This study investigated the effect of surface hydrophilicity on the hydrogen evolution reaction (HER). The water contact angles of the nickel phosphorous (NiP) films were controlled from 40.3 to 77.2° with imperceptible differences in their intrinsic electronic structures and surface areas. Electrochemical analyses and in situ visualization of the gas evolution on the NiP films indicated that an increase in the hydrophilicity of the electrocatalysts reduced the size of gas bubbles formed on the NiP films and shortened the duration of the bubbles' stay on the NiP surface. A faster gas departure enabled continuous participation of the electrocatalyst surface in hydrogen evolution, leading to a stable electrochemical behavior of the electrocatalyst and a decrease in the overpotential at a given current density. A full-cell test revealed that the enhancement of hydrogen bubble departure on a hydrophilic NiP surface with a contact angle of 40.3° reduced the overpotential by 134 mV at a current density of 100 mA/cm2 compared to a more hydrophobic film with a contact angle of 77.2°.

Dendritic Ag (a CO2-to-CO reduction catalyst) has been synthesized on carbon paper (CP) using pulse electrodeposition to fabricate a gas diffusion electrode. A combination of sonication and pulse deposition facilitated mass transfer of Ag ions to the CP, enlarging the catalyst active surface area without significantly changing the Ag crystalline structure. The current density of CO2 reduction was proportional to the surface area of dendritic Ag. Further improvements in performance were achieved by adding polyethylene glycol to the CO2 reduction cell catholyte that removed the CO gas bubbles produced at the electrode surface. The fabrication methods presented herein suggest an effective gas diffusion electrode for application in the membrane-electrode-assembly-type single cell for electrochemical CO2 reduction.

Organic additives play an important role in regulating film growth and properties in Cu electrodeposition. 3‑Mercapto‑1‑propane sulfonate (MPS) and its dimer bis(3‑sulfopropyl) disulfide (SPS) are representative accelerators that promote Cu electrodeposition rate. In this study, the formal reduction potential of SPS to MPS was determined by measuring the equilibrium constants of thiol–disulfide interchange reactions with the reference thiol/disulfide pairs by 1H nuclear magnetic resonance (1H NMR) spectroscopy. The calculated formal reduction potential of SPS to MPS was 0.153 V (vs. standard hydrogen electrode). Based on this calculation, the cell potentials of Cu(I)(thiolate) formation reaction with either SPS or MPS, which is a key reaction in accelerating mechanism, were also estimated by ultraviolet–visible absorption and 1H NMR spectroscopies: they were found to be 0.202 V and 0.214 V for SPS and MPS, respectively. The positive cell potential indicates that the formation of Cu(I)(thiolate) complexes is thermodynamically favorable in the presence of additives.

The intrinsic solubility of a gaseous substance and its dissolution rate play important roles in carrying out electrochemical reaction of gaseous reactant, in addition to the activity of catalyst. We tried to increase the solubility and dissolution rate of N2O by introducing Taylor vortices using a Couette-Taylor flow (CTF) mixer and investigated how the enhanced N2O dissolution affected the electrochemical reduction of N2O. The solubility and saturation time were estimated by electrochemical measurement of N2O concentration in the electrolyte solution. It was found that the Taylor vortices could not only increase the solubility of N2O but also reduce the time required to saturate the electrolyte with N2O. Furthermore, a high N2O conversion rate via electrochemical reduction was obtained with the introduction of Taylor vortices. We proved that an enhanced solubility and dissolution rate of the gaseous substance could be attained by using a CTF mixer as one of the alternatives for enhancing the electrochemical reaction of a gaseous substance in an aqueous electrolyte solution.

This study introduces the role of machine learning in improving the electrochemical analyses for the simultaneous quantifications of multiple chemicals. Here, Cu electrolyte containing Cl− and polyethylene glycol as additives was employed as a model analyte. These additives, which are redox-inactive when adsorbed onto the surface of an electrode, significantly affect Cu redox reactions. Conventional analyses cannot reveal the detailed dynamic changes in these additives owing to inherently weak signals and interference between the adsorbates. Thus, this study demonstrates how a combination of electrochemical analyses and neural network-based machine learning can identify and quantify four different additives from a single voltammogram, overcoming the present limitations. Further, instead of simply increasing the amount of data for training, chemical treatment is applied based on an understanding of Cu–adsorbate interactions to improve the performance of machine learning-based analyses. The developed method can also advance the simultaneous electrochemical analyses of other multicomponent systems.

For the electrochemical reduction of CO2 to CO, a dendrite-type Ag catalyst was fabricated via an electrodeposition method in an ammonia-based Ag deposition solution containing ethylenediamine (EN) as an additive. The influence of electrodeposition parameters on the properties of this catalyst was examined and further correlated with CO production efficiency. The addition of EN changed the intensity ratio of (220) vs. (111) planes in the Ag catalyst, which was shown to be proportional to the CO production activity. Furthermore, EN modified the chemical shift of Ag3d5/2 in the negative direction, increasing the CO production efficiency. Under optimized deposition conditions (–0.45 V vs. Ag/AgCl, 40 mM EN), which were a compromise between intensity ratio and chemical shift, the fabricated Ag catalysts exhibited the highest Faradaic efficiency and mass activity for CO during CO2 electrolysis in 0.5 M KHCO3. The experimental correlation between CO production efficiency and the crystalline/electronic structures of the catalyst suggested guidelines for further improving the Ag catalyst activity.

Herein, bimetallic Ag/Cu nanowires (NWs) are prepared by electrochemical synthesis of Cu NWs and subsequent Ag galvanic displacement for the electrochemical reduction of CO2 to CO. The delicate execution of the displacement fabricates bimetallic NWs that possess controlled surface composition. The surface composition of NW is precisely controlled by varying the displacement time, and it is revealed by numerical and experimental methods that the catalytic activity is closely affected by the composition. The surface coverage of Ag measured based on under potential deposition according to the displacement time ranges from 70% to 94.3%. An increase in the Ag surface composition results in an improvement in the CO Faradaic efficiency from 29.8% to 39.6% and a significant increase in CO partial current density compared with Cu NWs and Ag foil. Namely, the catalytic activity of Ag/Cu NWs is dependent on the Ag coverage, and is governed by scaling relation.

In this study, we investigated the effect of reducing agents to decrease the chemical decomposition of SPS. We added reducing agents (hypophosphite, formaldehyde, glyoxylic acid, hydrazine, and oxalic acid) into the Cu plating bath and examined their effects on the voltammetric response, bath performance, and stability of SPS. Among these, hydrazine and oxalic acid resulted in the formation of precipitates, and thus could not be used for accurate analysis. Hypophosphite was electrochemically active in the cathodic region due to the reduction of metallic phosphite, which led to errors in the CVS analysis. Therefore, it was determined that only formaldehyde and glyoxylic acid could be used as reducing agents in Cu electrolytes. Formaldehyde reduced the rate of SPS decomposition more effectively. The bath performance with and without formaldehyde was evaluated by performing a via-fill test. Consequently, when formaldehyde was not present, SPS was rapidly decomposed by Cu+, and the filling performance became poor after aging for 3 h. However, when formaldehyde was present, the filling performance was maintained for up to 9 h and SPS decomposition in the open-circuit condition rarely occurred. These results indicate that formaldehyde reduces the number of active radicals, thereby reducing the chemical oxidation of SPS.

A three–additive combination of an accelerator, a polymeric suppressor, and an organic leveler is typically utilized in the electrodeposition process to achieve Cu bottom–up filling of microvias on printed circuit boards. The use of several organic chemicals makes maintaining the performance of the electrolyte and additives more complicated due to the decomposition of the organic additives. As a replacement for the organic levelers, inorganic levelers, such as bromide ions, can avoid this problem since halide ions cannot produce organic by–products. This study investigates the effects of bromide ions on the adsorption of polymeric suppressors and accelerators and the influence of the concentration ratio of bromide ions and the accelerator on the bottom–up filling of microvias. The electrochemical analyses reveal that the bromide ions are adsorbed on the Cu surface and interact with the polymeric suppressor, increasing the suppression effect. In addition, bromide ions combined with the polymeric suppressor retard adsorption of the accelerator, and forced convection enhances the inhibitory effect of bromide ions. Electrochemical analyses also suggest that the accelerator to bromide ion concentration ratio is critical for controlling the surface activity for Cu electrodeposition and dictates the bottom–up filling characteristics. Microvia filling experiments indicate that in the optimum concentration ratio range (i.e., 0.2

The microstructural changes in electrodeposited Cu films during self-annealing is demonstrated in this study. The structural change is strongly influenced by the organic additives in the Cu electrodeposition. The use of either polyethylene glycol (PEG) or bis-(3-sulfopropyl) disulfide (SPS) decreases the Cu(111) grain size of deposited films, as the adsorption of the additives suppresses the surface diffusion of the Cu ions during the electrodeposition. After the electrodeposition, the average grain size of the deposited film was simultaneously increased by 10% in a self-annealing process to reduce the defect energy, which is mainly composed of the surface energy of the grains. Meanwhile, the grain grew 4 times larger than the as-deposited grain size during the self-annealing when both the PEG and SPS were introduced. The drastic grain growth was attributed to the accumulation of a high defect energy in the deposited film. The dynamic interaction between the co-adsorbed PEG and SPS on the Cu surface during the electrodeposition promotes an unoriented dispersion-type deposition, resulting in high-strain energy as well as surface energy. Releasing the strain energy accumulated by the high density of misorientation also leads to the simultaneous growth of Cu(200) grains.

In an attempt to ameliorate the poor cyclability of LiNi0.5Mn1.5O4 at elevated temperature, quercetin is applied as an additive. The irreversible oxidative behavior of quercetin is thoroughly investigated by electrochemical method. The improved cyclability of the quercetin-containing cell at high temperature implies that by forming robust and less-resistive SEI, quercetin is preferentially oxidized and passivates the LiNi0.5Mn1.5O4 electrode. EIS result coherently suggests that the quercetin-added electrolyte forms a more compact and Li-ion conducting interface. The surface sensitive XPS analysis confirms that the presence of quercetin restrains the formation of LiF, suppresses the reaction of PF5, and alleviates Mn dissolution. Meanwhile, ICP-MS analysis affirms the effectiveness of quercetin against Mn dissolution. The self-discharge experiment which exhibits the retained charged state of LiNi0.5Mn1.5O4 at high temperature, gives convincing evidence of the effect of quercetin. Intensive analyses confirm that quercetin can effectively prolong the cycle-life of LiNi0.5Mn1.5O4 at elevated temperature. We envision its potential and practical usage as an electrolyte additive for high-voltage cathode.

Si has been an attractive negative electrode material for high energy density Li-ion secondary battery owing to its largest theoretical capacity of 4200 mAh/g. However, the volume change caused by a large degree of lithiation and delithiation results in the formation of severe cracks and the exfoliation of active Si from current collector, which ultimately deteriorates the battery performance. Therefore, the cycle-life of active Si material should be improved to apply it to secondary batteries. In this study, we attempted to improve the performance of Si film electrode by fabricating it with sawtooth and pyramidal patterns via the microelectromechanical systems process. In addition, the effect of Si electrode morphology on its charge/discharge behavior was investigated. The capacity changes of the electrodes during 50 cycles were measured. The remaining Si on the current collector and its surface morphology were observed afterward to correlate with the electrochemical behavior. The experimental results show that the pyramidal Si electrode exhibited better cycle retention than any other electrodes by relaxing the stress and mitigating the exfoliation. This study shows that the structural modification may benefit the cycle-life of Si film electrode.

Ag, Ag–Cu and Cu dendrite catalysts were electrochemically prepared on a Cu foil substrate to investigate their catalytic activity and selectivity for electrochemical CO 2 reduction to CO. As the Cu content increased, the morphologies of Ag–Cu dendrite catalysts changed significantly from round to flower-like shapes accompanied by a decrease in branch size of the dendritic structure. A crystallographic study of the Ag–Cu dendrite catalysts demonstrated the formation of Ag and Cu co-deposits, while a compositional characterization confirmed the presence of a Cu-rich surface. Among the synthesized dendrite catalysts, the Ag 100 dendrite catalyst achieved the highest CO faradaic efficiency of 64.6% at a constant potential of −1.7 V SCE in CO 2 -saturated 0.5 M KHCO 3 electrolyte. However, the catalytic activity of Ag 57 Cu 43 dendrite catalyst was 2.2 times higher than that of the Ag 100 dendrite catalyst, in terms of Ag mass activity. By controlling the composition of Ag and Cu, direct formation of syn-gas or enhancement in the mass activity to CO production was achievable.

In this study, a polyethylene glycol-based organic additive, with quaternary ammonium cation functional groups linked to a naphthalene rings at both ends was synthesized, for through silicon via (TSV) filling. The synthesized additive strongly suppressed Cu electrodeposition under convection and successfully bifurcated the deposition surface of TSVs into active and passive regions, allowing defect-free TSV filling. However, there was a variation in TSV filling uniformity depending on the additive chain length. The chain length was adjusted using polyethylene glycol of various molecular weights as a starting material for the additive. The electrochemical investigation revealed that the chain length was related to the re-adsorption rate during Cu electrodeposition, which is critical in TSV filling. At the optimal chain length, uniform and defect-free bottom-up TSV filling was successfully achieved and TSV filling time was reduced to 500 s.

In this study, superconformal cobalt filling of submicron trenches by electrodeposition is investigated in the presence of 2-mercaptobenzimidazole (MBI), which suppresses both cobalt deposition and the hydrogen evolution reaction (HER). The mechanism through which this single additive enables superconformal cobalt filling is investigated. The formation and breakdown of the suppression layer are characterized by linear sweep voltammetry and chronoamperometry. The convection-driven local concentration of MBI exerts different suppressing effects on cobalt reduction and the HER, leading to a change in the deposition rate and the current efficiency of cobalt. These phenomena induce a deposition rate differential between the top and bottom of the submicron trench, enabling bottom-up cobalt filling with a V-shape profile.

Copper electroless deposition for the formation of electrically conductive seed layers is important in the manufacturing process of printed circuit boards. As the size of electrical devices decreases, the seed layer also needs to be thinner and its uniformity is highly stressed. In this study, Pd ion adsorption and Cu electroless deposition, which are the most crucial steps in seed layer deposition, were controlled through forced convection. Without forced convection, the seed layers at the top and bottom sides of the microvia are of different thicknesses, which can cause defects. The application of forced convection in Pd ion adsorption uniformly deposited the seed layer by suppressing the adsorption of Pd ions on the top side of the microvia. Furthermore, forced convection on copper electroless deposition enhanced overall mass transfer of reactants such as cupric ions and formaldehyde, and accompanying the deposition rate on the top and bottom sides, which balanced the thickness of the seed layer on the top and bottom sides. Thus, forced convection in Pd ion adsorption and Cu electroless deposition compensated for the suppression of the Pd ion adsorption and improved the uniformity of seed layers on the microvia substrates.

The mechanisms of cathodic and anodic decomposition of polyethylene glycol (PEG), a suppressor in the Cu electrodeposition process, were examined via both cyclic voltammetry stripping (CVS) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) analysis under open-circuit, unpowered closed-circuit, and electrolysis conditions. Under the open-circuit conditions, PEG decomposition occurred only at the cathode (Cu electrode), owing to the effect of the Cu+ ions. Under the unpowered closed-circuit conditions, PEG degraded at both electrodes (Cu and Ir/IrOx on Ti/TiOx) through the galvanic proportionation reaction, owing to which Cu+ was also formed at the anode. Under the electrolysis conditions, PEG also was degraded at both electrodes, but a difference in the average PEG molecular weights (MWPEG) between the two electrodes was observed after 48 h. The PEG breakdown at the cathode appeared to be related to the Cu+ ions, while that at the anode was caused by the •OH radicals formed by water splitting. Remarkably, the PEG decomposition rate under electrolytic conditions was reduced compared with that obtained under the closed-circuit conditions, indicating a lesser extent of radical formation. Therefore, it is concluded that PEG degradation did not proceed through a direct electrochemical reaction, but rather through a radical-induced chemical reaction.

The density functional theory (DFT) calculations were performed to investigate the catalytic activities of Pd, Cu, and PdxCuy alloy catalysts for N2O reduction reaction (NRR). The activation and dissociation of N2O on PdxCuy catalysts were explored. The rate-determining step for the NRR was the dissociation of N2O into N2 and O. The electronic structure of PdxCuy alloys was determined by both ligand and strain effects, but was not closely related to the catalytic activity for NRR because two kinds of surface Pd and Cu atoms are differently involved in active sites for molecular adsorption and dissociation. Owing to the different role of Pd and Cu in NRR, the PdCu catalyst had both strong N2O adsorption strength and easier N2O dissociation than did pure and Pd3Cu catalysts, and therefore had the highest catalytic activity for NRR among the PdxCuy alloy catalysts. These fundamental findings were further applied to predict the thermal and electrochemical NRR.

The effect of complexing agents on Co oxidation/dissolution in alkaline solution was investigated for Co chemical-mechanical polishing (CMP) and post-CMP cleaning processes. The oxidation and dissolution properties of Co in a solution are greatly affected by complexing agents, which could influence the performance of Co CMP and post-CMP cleaning processes. Herein, three complexing agents, glycine, ethylenediaminetetraacetic acid (EDTA), and citric acid were studied. It was revealed that the complexing agents determined Co dissolution rate depending on the presence or absence of H2O2. Glycine showed a higher Co dissolution rate than EDTA and citric acid in the absence of H2O2, while EDTA showed the highest dissolution rate in the presence of H2O2. Negligible dissolution was observed with citric acid, regardless of the presence of H2O2. Electrochemical impedance and UV–Vis spectroscopies found that the difference in Co dissolution rates was related to Co oxidation rate and complexation capability of each complexing agent. Glycine showed a higher Co oxidation rate than EDTA, while EDTA had a much higher complexation capability than glycine. Citric acid exhibited the lowest Co oxidation rate and complexation capability, resulting in the slowest Co dissolution rate.

An ionic liquid/organic solvent mixture was adopted as an electrolyte for the electrochemical reduction of N2O. The ionic liquid and organic solvent used for the electrolyte were 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and propylene carbonate (PC), respectively. The use of [BMIM][BF4] in place of aqueous solutions improves the solubility of N2O and also avoids the hydrogen evolution reaction, which is the main side reaction in an aqueous solution. The low electrical conductivity and high viscosity of [BMIM][BF4], the main disadvantages in the context of electrochemical reactions, were compensated on introducing PC. The composition of the [BMIM][BF4]/PC was optimized considering both the electrical conductivity and N2O stability in the solution. For the optimized [BMIM][BF4]/PC, a high faradaic efficiency (>90%) was achieved for N2O reduction to N2. Keywords: N2O, Electrochemical reduction, Ionic liquid, Non-aqueous solution

Monitoring the concentration of additives in the Cu electroplating process is becoming important, but is challenging, because the interaction between additives makes it difficult to observe the independent behavior of a target additive. In this paper, iodide ion (I−) was introduced as a chemical agent to disrupt the anti-suppression action of bis-(sulfopropyl)-disulfide (SPS) accelerator to monitor the concentrations of polyalkyl glycol (PAG) suppressor, based on its inhibiting action to accelerator in a vigorous mass-transport environment. Even a small amount of SPS in target solutions interfered with the determination of PAG concentration, when using the cyclic voltammetry stripping (CVS) method as a monitoring tool. I− could hinder the SPS-mediated breakdown of the surface passivation layer, even in higher concentration of SPS, allowing selective determination of PAG, free from interference by SPS. This is presumed to be due to the formation of the ionic compound, copper (I) iodide (CuI) with I−-involved PAG complex on the electrode surface. By introducing I−, modified CVS analysis was repeated, and the results revealed that adding I− totally suppressed the behavior of SPS, and yielded determined PAG concentrations that were similar to the actual values.

Increasing the electrochemical surface area of electrocatalyst is important for achieving high Faradaic efficiency with rapid reaction rate in bulk electrolysis of gaseous reagents. Hence, we fabricated efficient and cost-effective porous indium foam for the electrochemical reduction of nitrous oxide by using electrodeposited copper foam as the template. Indium grew on the surface of copper foam, preserving the original porous foam structure. The electrochemical investigation on indium revealed a high selectivity and a fast reaction rate of indium foam electrode towards nitrous oxide electroreduction. Keywords: Electrochemical reduction, Nitrous oxide, Indium foam, Copper foam

Through silicon via (TSV) technology has been researched for 3-dimensional packaging of electronic devices, and Cu electrodeposition has been used for TSV filling. The organic additives are one of the most important factors in Cu electrodeposition affecting Cu gap-filling, and the leveler usually plays a decisive role. In this research, iodide ion (I−) is adopted instead of organic leveler for Cu bottom-up filling. The behaviors of I− are investigated by various types of electrochemical analyses. Especially, the influences of I− on the adsorption of the accelerator and suppressor are extensively studied, and it is confirmed that I− makes the suppression layer robust while reducing the adsorption of the accelerator. Also, it was observed that the effect of I− is greater under the strong convection of electrolytes than without convection, meaning that I− could induce selective deposition at the bottom of the features. Based on this, TSV-scaled trenches are successfully filled by potentiostatic Cu electrodeposition in the presence of the accelerator, suppressor, and I− without any organic levelers.

Void-free filling of TSV-scaled trenches is achieved by adding a new leveler with an accelerator and polymeric suppressor. Leveler containing two quaternary ammonium salts allows for the galvanostatic bottom-up filling. In addition, the filling time is reduced by applying the step current comprising a first step to establish a growing surface and a second step to reduce the filling time. The deposition height of the growing surface during the first step critically determines the filling performance. By modulating the step condition, the filling time reduced by 47% compared to the constant current deposition. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0061510eel] All rights reserved.

Through Silicon Via (TSV) technology is essential to accomplish 3-dimensional packaging of electronics. Hence, more reliable and faster TSV filling by Cu electrodeposition is required. Our approach to improve Cu gap-filling in TSV is based on the development of new organic additives for feature filling. Here, we introduce our achievements from the synthesis of choline-based leveler to the feature filling using a synthesized leveler. The choline-based leveler, which includes two quaternary ammoniums at both ends of the molecule, is synthesized from glutaric acid. The characteristics of the choline-based additive are examined by the electrochemical analyses, and it is confirmed that the choline-based leveler shows a convection dependent adsorption behavior, which is essential for leveling. The interactions between the polymeric suppressor, accelerator, and the choline-based leveler are also investigated by changing the convection condition. Using the combination of suppressor, accelerator, and the choline-based leveler, the extreme bottom-up filling of Cu at trenches with dimensions similar to TSV are fulfilled. The mechanism of Cu gap-filling is demonstrated based on the results of electrochemical analyses and feature filling.