bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) AC Impedance Studies on Electrode/Electrolyte Interface in Lithium-Ion Batteries
Authors: Abe Takeshi
Published: February 2020

Lithium-ion batteries have been extensively used for portable devices and electric vehicles. For the latter use of lithium-ion batteries, rapid charge is required in addition to long cycle lives, high safety, etc. We have focused on the rate capabilities of lithium-ion batteries by considering the lithium-ion transfer at electrode/electrolyte interface and also ion transport inside composite electrodes.

Lithium-ion transfer at electrode/electrolyte interface was studied by using various model electrodes. Highly oriented pyrolytic graphite (HOPG) was used as a model electrode of graphite negative electrode. Since the basal plane of HOPG has limited reaction sites, we can observe large lithium-ion (charge) transfer resistances by Ac impedance spectroscopy. Then, it is quite easy to evaluate the activation energies for lithium-ion transfer at HOPG electrode. The values are ranging from 50-60 kJ/mol. For the positive electrodes, we used thin films prepared by pulsed laser deposition (PLD). We fabricated LiCoO2 and LiMn2O4 thin film electrodes. By using the thin films, the lithium-ion transfer resistances become also clear. Again, the activation energies were obtained and the values are almost the same with those of graphite.

Based on the activation energies for lithium-ion transfer at negative and positive electrodes, it becomes quite clear that the rate capabilities of lithium-ion batteries at the lower temperature region are quite dependent on the lithium-ion transfer resistances.

We then focused on the ion transfer resistances inside the composite negative and positive electrodes. We used the four-probe cell to evaluate the ion transport resistances inside composite electrodes by Ac impedance spectroscopy. Consequently, the ion transport inside composite electrodes was found to be very slow for the high density electrodes.

By the above results, I will talk about the rate determining steps of lithium-ion batteries at the conference.

Acknowledgment

This work was partially supported by CREST, JST.
(Invited) The Impedance of Bioelectrochemical Interfaces
Authors: Rueda Manuela , Prieto Francisco , Alvarez-Malmagro Julia
Published: February 2020

Biological relevant molecules are known to get adsorbed at the electrode/electrolyte interface and the study of their adsorption is interesting in relation to biosensors design and development of supra-molecular vectors for drugs delivery. On the other hand, the structure and electrical properties of biomembranes are frequently modeled by modifying electrode surfaces with lipidic films. The study of these lipidic film coated electrodes is also relevant in relation to drugs delivery vectors. Both cases of electrode interfaces are usually characterized by capacitance measurements as a function of potential with the implicit assumption of a serial RC model circuit for the metal/solution interface. However, the application of the electrochemical impedance spectroscopy (EIS) and the corresponding analysis of data as a function of the frequency and of the applied potential to the electrode can provide detailed information about the kinetics of adsorption1,2, biomembrane reorganization phenomena and electron transfers through the film3.

In this communication the application of EIS to bioelectrochemical interfaces is illustrated by studying examples of the two kinds of electrode interfaces. The adsorption of adenine, one of the DNA bases, on single crystal Au(111) electrode is presented as an example of a Gibbs adsorption electrode interface, in which the adsorbate is present in the metal and the electrolyte phases, while the study of modified electrodes with phospholipid films exemplifies the electrochemical behavior of organized biomembrane coating the metal with the polar heads of the lipidic chains directed towards the electrolyte solution part of the interface.

The experimental procedures In the case of the two kinds of interfaces have to be designed in order to avoid interference of surface reconstruction phenomena (in the case of the work with single crystal electrodes) or film reorganization phenomena (in the case of phospholipids modified electrodes).

The results about adenine adsorption as a function of the pH of the solution allow us to evaluate the kinetics of the adsorption and their correlation with results previously obtained by the authors using FT-IR-spectro-electrochemical methods1,2. The results about phospholipids film coated electrodes allows us to conclude about the stability of the film as a function of the electric field and to analyze the plausible electron transfer through them, when adding electroactive compounds to the solution phase.

[1].- M. Rueda, F. Prieto, A. Rodes, J.M. Delgado, Electrochim. Acta, 82 (2012) 534

[2].- J. Alvarez-Malmagro, F. Prieto, M. Rueda, A. Rodes, Electrochim. Acta, 140 (2014) 476

[3].- M. Rueda, F. Prieto, I. Navarro, R. Romero, J. Electroanal. Chem. 649 (2010) 42
EIS Study on Solid Electrolyte Deposition of Copper Film
Authors: Narui Yuka , Kojima Kenta , Iwabuchi Toru , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki , Yanagimoto Hiroshi , Hiraoka Motoki , Iisaka Hirofumi
Published: February 2020

Copper plating is generally used for the fabrication of a printed circuit board of electronic device. The patterning is carried out by masking with insulator for the partial plating on the substrate. Solid electrolyte deposition (SED) method using solid electrolyte instead of liquid electrolyte is strong candidate for an alternative plating technique without masking because the copper is deposited only on the substrate contacted with solid electrolyte. Figure 1 shows the scheme of electrochemical cell for copper SED. The electrochemical cell is quite simple, namely, a thin solid electrolyte membrane is sandwiched by substrate and counter electrode. The substrate works as a cathode during copper deposition. Copper plate is used for the counter electrode because cupric ions are dissolved into the solid electrolyte membrane by the anodic reaction. Cation-exchange membrane is used for the solid electrolyte since the mass transfer of cupric ions is controlled by migration originating from the voltage between two electrodes. The solid electrolyte membrane is immersed in CuSO4solution to absorb cupric ion by ion-exchange for over 24 hours before the polarization. The copper is deposited on the substrate when the potentiostatic polarization is performed.

Advantages of SED comparing with common electro-deposition are written as follows.

・Electrochemical cell is very simple.

・Post-processing is simple because of no masking.

・It’s environment-friendly because of a small quantity of liquid．

・The deposition rate is very fast because driving force of mass transfer of cupric ions is migration and the concentration of cupric ions is maintained constantly in the solid electrolyte membrane.

The deposition rate is determined by three steps, which are anodic dissolution of copper counter electrode, the mass transfer of cupric ions in solid electrolyte membrane and the cathodic reaction on the substrate. Therefore, the measurements of 3D electrochemical impedance were carried out to discriminate above-mentioned three contributions to the deposition rate of copper by SED.

Reference:

1) K. Akamatsu, Y. Fukumoto, T. Taniyama, T. Tsuruoka, H. Yanagimoto, H. Nawafune, Langumuir, 27, 11761-11766 (2011).

Figure 1
Analysis of Warburg Impedance of Lithium-Ion Rechargeable Batteries By Wavelet Transformation
Authors: Gamano Yusuke , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: February 2020

An electrochemical impedance spectroscopy (EIS) is useful method to investigate the electrode structures in the lithium-ion Rechargeable batteries (LIRBs) because time constants in the electrochemical impedance can be discriminated. The impedance spectrum is usually measured by using a Frequency Response Analyzer (FRA) whose principle is based on Fourier Transformation (FT). In the present paper, we calculated Warburg impedance from time series data of voltage and current of batteries by Wavelet Transformation (WT). WT is one of the calculation methods to transform data in time domain to those in frequency domain. We selected complex Morlet mother wavelet (CMMW) to determine impedance spectrum because CMMW is composed of complex sinusoidal wave and Gaussion window function1).

The voltage response after current step imposed to battery is calculated by the following equation.

  V(t) = V0
’
 +RT/(nF)ln((c
E
*-2i√t)/(nFA√(πD
E)))/(c
S(0,t)) (1)

In the equation (1), V0’
is voltage at steady-state, R is gas constant, T is room temperature, F is Faraday constant, cE* is Lithium-ion concentration in the electrolyte, i is current, t is time, A is electrode surface area, D
E is diffusion coefficient and c
S is Lithium-ion concentration in the active material. This equation was derived from the Fick’s second law of diffusion. The Warburg impedance was determined from time series data calculated by theoretical equation (1), indicating that the electrode reactions are under diffusion control. The procedure to determine electrochemical impedance by WT is described as follows. First, a current step signal of 0.372 [A] was applied to the system. Then, the voltage response was calculated by the equation (1) after current step at 100 s. The wavelet coefficients of current and voltage were obtained by WT. The complex impedance was calculated by cross-spectrum of the wavelet coefficients. Finally, we obtained the impedance spectrum. The impedance spectrum determined by above-mentioned procedure indicated a typical locus of Warburg impedance, which is straight line whose slope is 45 degree. This method was applied to determination of the impedance spectra of a commercial battery (UR18650A). The diffusion coefficient of lithium-ion was estimated by the impedance spectrum.

References:

[1] Y. Hoshi, N. Yakabe, K. Isobe, T. Saito, I. Shitanda, M. Itagaki, J. Power Sources, 315, 351-358 (2016).
Trials, Tribulations, and Some Success in Developing Modeling Tools for the Electrochemical Industry
Authors: Landau Uziel
Published: February 2020

The fundamentals of computational modeling of current distribution in electrochemical cells have been known and practiced in academic settings since the early 50’s. However, unlike conventional chemical facilities, electrochemical cells were still being designed empirically in the 80’s and 90’s, and to significant extent, empiricism prevails in the electrochemical industry even today. The underlying reasons for this slow penetration of modeling applications are discussed.

The advent of personal computers in the early 80’s presented an opportunity to provide wide access to quantitative modeling throughout the electrochemical industry. The considerations that guided the design of the first commercial CAD software package of electrochemical cells, “Cell-Design”, and its commercialization strategy are presented, including the roles of industry and government in this endeavor. By the late 80’s and throughout the 90’s additional software packages, with different features and marketing strategies became available. The relatively recent introduction of an electrochemical module to Comsol, presented yet another stage in modeling capabilities of electrochemical cells that became accessible to the industry. The different features and marketing strategies of the different modeling packages are described.

A major barrier to wide-spread penetration of quantitative modeling within the electrochemical industry has been the lack of property data, particularly as related to many different plating solutions with proprietary additives. To overcome this limitation, that affects mostly the small plating companies with limited access to electroanalytical tools and expertise, the “L-Cell”, a device for fast determination of kinetics parameters, has been introduced. The capabilities, advantages, and limitations of this instrument, in comparison to other tools, ranging from automated and specialized devices to the aging and simplistic, but still widely used, “hull-Cell”, are discussed.

Challenges facing the electrochemical industry and opportunities that will enable it to meet future technological needs, including, but not limited to modeling capabilities, are critically discussed. Tasks that can be best carried out in academic institutions and others that are more effectively accomplished in industry and the interactions between the two, based on the author’s experience, are presented.
(Invited) Stable Nanocrystalline Electrodeposits: Case Studies Spanning from Theory to Products
Authors: Schuh Christopher Allan
Published: February 2020

Although many metals and alloys can be electrodeposited with nanoscale internal structure, few of these are stable enough for engineering use. Many more have processing and property disadvantages that prohibit commercialization. This talk will describe a general recipe developed at MIT and subsequently at Xtalic Corporation (Marlborough, MA) for the design of stable and deployable nanocrystalline electrodeposits. Such deposits have the strength, hardness and wear benefits well known to nanostructured metals, but with a stabilized structure that resists coarsening even under significant heating conditions. Three case studies will be discussed, for alloy coatings based on Ni, Ag, and Al. With emphasis on the basic theory of alloy design, through reduction to practice, and to commercialization at the level of billions of coated components, the talk will highlight the role of thermodynamic thinking in streamlining the search for product-viable electrodeposits.
(Invited) Ceramic Membranes for Gas Separation and Electro-Synthesis: Effect of Surface and Interfaces
Authors: Chen Yu , Liu Meilin
Published: February 2020

Electrochemical cells based on membranes represent a highly efficient and economically viable approach to gas (hydrogen and oxygen) separation and electrosynthesis. For example, a cermet membrane consisting of a ceramic proton conductor and a metal (e.g., nickel) could be used for recovery of high-purity hydrogen from synthetic gas mixtures during various industrial processes such as coal gasification and water gas-shift reaction. Similarly, a cell based on proton conductor can be used for hydrogen production and ammonia synthesis. In particular, yttrium/ytterbium doped barium zirconate-cerate (BZCYYb) exhibits the highest proton conductivity in the intermediate temperature range. Further, BZCYYb-based materials have high tolerance to sulfur poisoning and coking under typical conditions for hydrocarbon reformation. To date, however, there is little mechanistic understanding of the surface electrochemical reactions. A fundamental understanding of the charge and mass transport processes associated with surface reactions is vital to achieving rational design of a new generation of membranes for gas separation and electro-synthesis. In this presentation, we will highlight our recent progress in understanding the effects of surface and interfaces on gas separation processes, aiming at elucidating the mechanisms that control ionic transport and selectivity to desired product formation.
(Invited) Electrospun Nanofiber Composite Bipolar Membranes
Authors: Pintauro Peter N. , Wycisk Ryszard , Cunningham Marc , Shen Chunhui
Published: February 2020

Bipolar membranes, typically a laminate of an anion-exchange and cation-exchange membrane, have the unique capability to split water at a potential as low as 0.8 V while conventional electrolysis requires at least 1.2 V. Such membranes are employed in a number of important industrial processes, including the production of mineral acids, the recovery of organic acids from fermentation processes, pH control, and ion-exchange resin regeneration. The use of bipolar membranes in electrodialysis separations eliminates unwanted salt efflux and disposal problems and offers significant savings in electrical energy consumption. Recently, bipolar membranes have also been examined for use in self-humidifying hydrogen/air fuel cells, where the recombination of electrochemically generated hydroxide ions and protons at the bipolar junction produces water that improves membrane hydration, with higher power output at reduced feed gas humidity conditions.

We report here for the first time on the design, fabrication, and testing of a new bipolar membrane that was made by polymer nanofiber electrospinning, where the anion-exchange polymer is quaternized poly(phenylene oxide) and the cation-exchange polymer is sulfonated poly(ether ether ketone). This new membrane has a 3-D nanofiber bipolar junction with a very high interfacial area, unlike the typical 2D planar junction. This extended junction morphology is important for two reasons: (1) it improves the attachment (adhesion) of the two ion-exchange layers so that ballooning/delamination is minimized or eliminated and (2) the increased bipolar junction surface area will lead to a better distribution of the water splitting reaction and lower membrane voltage drop for the same operating current density. The procedure for membrane fabrication will be described and the performance of electrospun films will be compared to bipolar membranes in the literature.
A Method for Effective Work Function Monitoring
Authors: Marinskiy Dmitriy , Loy Thye Chong , Edelman Piotr , Lagowski Jacek
Published: February 2020

The effective work function (EWF) is a critical gate parameter dependent on metal, dielectric, and interaction between them. As such, it requires stringent control, both in R&D stage and in manufacturing of advanced MOSFET’s. In this work we present non-contact charge-based EWF monitoring that brings advantages of cost-effectiveness and fast data feedback. The method extends our micro corona-Kelvin testing of dielectrics and interfaces in scribe-line boxes to EWF suitable configuration with a thin metal layer on a top of a dielectric.

Two key elements are used in the present method: 1) corona charge deposition on metal surface and 2) surface voltage measurement by Kelvin force microscopy. In a dynamic version of the flatband voltage determination, the surface voltage decay after corona charging is measured under modulated light conditions enabling parameter free extraction of VFB. Results for n- and p-type metals show sensitivity of VFBto EWF and agreement with results at end of the line CV measurements.

The micro corona-Kelvin method allows quantification of two more work function sensitive parameters: the silicon surface barrier, Vsb, and the tunneling barrier related to the band offset at the metal / high-k dielectric interface. Results for n- and p-type metals correlate with the expected behavior. Measurement of the silicon surface barrier, Vsb, can be especially attractive since it can be done on a blanket wafer with a thin metal layer over the high-k dielectric, providing means for high resolution mapping.

The third EWF sensitive parameter is obtained from the analysis of the tunneling current across the dielectric under negative bias condition, i.e. tunneling of electrons from the metal gate through the dielectric. Measured shifts of the tunneling barrier were consistent with EWF.
a Study on Via Filling Performance in a High-Aspect-Ratio Though-Silicon Via with Various Conditions of Leveler
Authors: Jin SangHoon , Lee Woon-Young , Lee Dong-Ryul , Lee Yu-Jin , Lee SangYul , Lee Min-Hyung
Published: February 2020

The void-free filling of high-aspect-ratio through silicon via (TSV) is one of the technical challenges for 3D integration. In order to fill the TSV without void, generally, copper was electroplated into an acid bath including organic additives of accelerator, suppressor and leveler. Especially, organic additives play important role on inhibiting the TSV internal void by interaction between them [1-4].

In this research, we investigate the effect of chemical properties of levelers in copper electroplating bath on TSV filling performance. As the result, it was determined that TSV filling performance was strongly affected by molecular weight (mol. wt.) and nitrogen weight percentage per a monomer (N wt. %) of leveler. Only the levelers having less than mol. wt. 10,000 and over 20 N wt. % can succeed to fill a TSV without void under high speed electroplating of 1.3ASD. This result proves that the leveler with low mol. wt and high N wt. percent can inhibit the faster electroplating at the upper edge of TSV effectively even at the high current density. We confirmed the progress of void-free TSV filling under the optimized leveler condition using cross sectional optical microscope (OM) images according to plating time as shown in Fig.1.

[1] H. Ling, H. Cao, Y Guo, H. Yu, M. Li and D. Mao, International Conference on Electronic Packaging Technology & High Density Packaging (2009) 860-862.

[2] K. Zou, H. Ling, Q. Li, H. Cao, X. Yu, M. Li and D. Mao, International Conference on Electronic Packaging Technology & High Density Packaging (2009) 103-106.

[3] L. Ma, H. Ling, M. Li, J. Sun, X. Yu and Y. Li, 14th International Conference on Electronic Packaging Technology (2013) 356-359

[4] R. Beica, C. Sharbono and Tom Ritzdorf, Electronic Components and Technology Conference (2008) 577-583

Fig.1. cross-sectional OM images of TSV electroplated under optimized leveler condition according to plating time: (a) 150 sec, (b) 300 sec (c) 600 sec (d) 700 sec

Figure 1
Effect of Degraded Additives on Under-Fill TSV
Authors: Ahmed Shafaat , Findeis Paul , Troung Connie Nga , Cheng Tien Jen , Grunow Stephan , Rothkranz Ronald , Oakley Jennifer , Graves-Abe Troy
Published: February 2020

In the past few years the 3D IC integration (3DI) stacking has emerged as a potentially novel approach for extending computing performance without the high cost of CMOS scaling. The 3DI stacking technology is thought to be the essential technology of the next generation high-end semiconductors which will provides improved performance, and reduced form factor for applications such as logic-memory integration, image sensors, MEMS, and LED. The through silicon via (TSV) is one of the main components for 3DI stacking. Copper plating has been used for TSV metallization due to its low resistivity, low cost, excellent plating efficiency, easy to integrate, excellent reliability and a unique bottom up fill capability in presence of additives in the plating bath. One of the major challenges in the TSV metallization by plating is embedded voids and underfill TSV. Among the many parameters in TSV plating; bath composition especially suppressor to accelerator ratio (S/A) significantly affects TSV under-fill. It has been seen that the additives also degrades over the shelf life aging depends on their storage condition. Since the degradation of both suppressor and accelerator is not happening in the same rate, the S/A ratio vary and thus found to be caused TSV under-fill.

Fig. 1(a) shows a cross-section SEM image of a TSV plated with BKM bath additives for 1600s. In contrast, Fig. 1(b) and 1(c) shows cross-section SEM images those were plated with same amount of BKM accelerator but with 10% and 25% less suppressor than the BKM respectively. It can be seen that the growth of copper inside the TSV increased~ 33% (with 25% lower suppressor) than the POR without increase of Cu film thickness on side wall, Chamfers and field area. Similarly, for a given suppressor, the copper fill rate can also varied by varying the accelerator concentration. In this paper, we will describe how additives affect the TSV under-fill and correlate the TSV under-fill with degradation of additives during their shelf life aging.

Fig. 1(a) Cross-section SEM image of a TSV deposited with BKM plating additives of accelerator and suppressor and plating process for 1600s. Fig.1 (b) and (c) shows cross –section SEM images of a TSV those were plated with same amount of BKM accelerator but 10 and 25% less suppressor respectively than the BKM condition but exactly same plating process and time as Fig 1a

Figure 1
Detection of Cuprous Ions By Micro Ring Electrodes on a TSV Side Wall
Authors: Hoang Ha Van , Kondo Kazuo
Published: February 2020

Copper electrodeposition in through silicon via (TSV) occurs in two steps with the intermediate is cuprous which has a certain role in filling of the TSV. The inhibition of the TSV outside is not only by inhibitors but also by the dispersion of cuprous complexes. Further, cuprous complexes remain inside of the via are almost deposited, and contribute to the acceleration of the via bottom filling. In this research, micro ring electrodes were made using silicon processing (Fig. 1). Five 5x5µm size micro electrodes, which were formed by platinum sputtering on a silicon substrate, have 10µm pitch. The microelectrodes were wired out. A SiO2 layer was covered over wires and left a 10x50µm space on the microelectrodes. A silicon substrate cap has a groove, size of 10µm width, 10m height and 50µm depth, was sputtered copper then it was pronated on the micro electrodes. Electrolyte baths using in the experiments contained 200g/L Cu2SO4.5H2O and 25g/L H2SO4 and were added additives depending on measurements. The cap was the disk electrode working at -50mV vs SCE, the micro platinum electrodes connected to a switch which wired to the ring cable of a potentiostat/galvanostat working at 500mV vs SCE. The disk currents were stable and the value was in the range -2µA to -3µA. The ring current was in the range of 0.2nA to 0.5nA. Measurement of three electrodes E1, E3, E5 showed that the ring current was highest at the electrode E5 without additives, however, in the present of Clˉ and SPS the electrode E1 had the highest current.

Figure 1
The Suppression Induced S-NDR Mechanism for Defect-Free Filling of High Aspect Ratio Features
Authors: Josell Daniel , Moffat Thomas P.
Published: February 2020

Superconformal electrodeposition in Through Silicon Vias for multiple metal systems is summarized and shown to be explained by models based on suppressor-induced, S-shaped negative differential resistance (S-NDR). As yet unpublished results for superconformal electrodeposition of Ni in TSVs using a Watts electrolyte containing a dilute suppressing additive are detailed and the filling morphology compared to previously detailed observations of superconformal Au deposition and bottom-up Zn and Cu deposition in TSVs. Voltammetric measurements for quantifying the kinetics of metal deposition, suppressor adsorption, and impact of one on the other are shown for the different systems. Experimental dependence of the superconformal filling behavior on deposition conditions including suppressor concentration, transport and deposition potential are described. Models based on S-shaped negative differential resistance (S-NDR) are shown to capture these trends and predict the filling geometries. The results demonstrate both the generality of the S-NDR mechanism for achieving void-free filling of large features by electrodeposition and the power of S-NDR based models for predicting filling evolution and designing effective processes.

Figure 1
Using Graphene As a Conducting and Barrier Layer for Filling through Silicon Vias with Co-W Alloy
Authors: Chen Yi-Yong , Dow Wei-Ping , Chang Ping-He , Li Hong-Qing , Lin Jing-Yuan
Published: February 2020

Usually, TSV fabrication is a dry process, including via formation by reactive ion etching, SiO2 isolation liner deposition, CVD or PVD TiN barrier layer and copper seed layer, and via filling with copper. Herein, we attempt to use graphene to simultaneously substitute the TiN barrier layer and the copper seed layer in order to simplify the TSV fabrication process. In addition, the coefficient of thermal expansion (CTE) of the filled copper often lead to failure in the TSV interconnects because the CTE of copper is much higher than that of silicon. The filled materials in the TSV with a high CTEs will induce large stresses at the interfaces between the filled material and silicon. To overcome this problem, we choose graphene to substitute the copper seed layer since the CTE of graphene is closer to that of silicon. Moreover, we select cobalt, which possesses not only a lower CTE but also a longer electromigration lifetime than those of copper, as the filled material of TSV. Tungsten can be co-deposited with cobalt, so that CoW alloy is formed in this work and the CTE of CoW alloy filled in TSV is lower than that of pure cobalt.

In this work, the effects of electroplating additives, electroplating baths and operating parameters on alloy composition, filling performance and thermal reliability performance of the electrodeposited CoW alloy from Co(NH2SO3)2•4H2O, NaWO4•2H2O, C6H8O7 and Na3C6H5O7•2H2O electrolyte are investigated. On the other hand, a linear sweep voltammetry (LSV) and galvanostatic measurements are carried out to electrochemically analyze these additives. The electrochemical behaviors of these electroplating additives are explored to explain the correlation between the suppression and the corresponding filling performance. The results indicate that the combination of suppressors with different molecular weights and a leveler can exhibit strong suppression and lead to CoW bottom-up filling of TSV.
A Cocoon-Shaped Copper Plating Filling Technique for through Hole Metallization
Authors: Mai Jhih-Jyun , Wen Shih-I , Dow Wei-Ping
Published: February 2020

Recently, with the electronic products tending to be light, multifunctional and a high speed transmission, the IC substrates and printed circuit boards (PCBs) must increase circuit density and be able to accommodate a lot of elements in a single device. In order to accommodate more elements in a single device, the circuit density of PCB and IC substrate have to decrease line width and distance between conducting lines, but their overall thickness must be thinner than before. It means that the conducting via or through-hole (TH) will be small and a thin surface copper layer is necessary.

In this work, we developed a copper plating formula composed of several additives to perform TH filling of an IC substrate. The results show that the copper plating formula can perform a highly selective TH filling. Copper was mainly plated in the TH and a thin surface copper layer was obtained outside the TH. The plated copper shape in the TH looks like a cocoon according to its cross-section, which can solve the dimple issue of current TH filling technology, even it can be used as copper bump for copper-to-copper connection.

Keywords: Through-hole filling, Printed circuit board, IC substrate, Copper Plating, Cocoon

Reference

W. P. Dow, H. H. Chen, M. Y. Yen, W. H. Chen, K. H. Hsu, P. Y. Chuang, H. Ishizuka, N. Sakagawa, R. Kimizuka, “Through-Hole Filling

by Copper Electroplating”, Journal of The Electrochemical Society, 2008, 155, D750-D757.
Electromigration Effects upon Cu/Ni/Sn-Ag and Cu/Ni/Sn-Ag-Cu Interfacial Reactions
Authors: Chen Sinn-wen , Chen Jing-wei , Lin Yi-cheng , Chang Tao-chih
Published: February 2020

Electromigration refers to the motion of atoms under the influence of an electric field. The electromigration effect most often is a result of momentum transfer from electrons, but it can be also caused by electrostatic force. The electromigration effect was discovered by Gerardin in 1861 [1]. The electromigration effect upon interfacial reactions and the resulted polarity phenomenon were first reported by Chen et al. [2,3], although electromigration effect upon the microstructures of a conduction line, such as void and whisker formation, had been intensively investigated much earlier. Understanding of electromigration effects upon interfacial reactions have become even more important nowadays because of thinner conduction lines, more interconnection joints, and higher electric current densities in the modern electronic products, such as products of 3D packaging. The interfacial reactions with and without passage of electric currents in the Sn-Ag/Ni/Sn-Ag, Sn-Ag/Ni/Cu/Ni/ Sn-Ag, Sn-Ag-Cu/Ni/Sn-Ag-Cu and Sn-Ag-Cu/Ni/Cu/Ni/Sn-Ag-Cu sandwich-type samples were examined at 150, 180 and 200oC. The main focus of this study is to understand the possible effects of Cu diffusion upon the Ni/Sn-Ag and Ni/Sn-Ag-Cu interfacial reactions. Two types of substrates were used, and they were 500mm-thick Ni foil and 500 mm-thick Cu foil plated with 50 mm-thick Ni. Two kinds of electricity-bias were conducted. One kind was with DC current and the other kind was with DC current but reversing the direction in the middle of the reaction time. Cu6Sn5 and Ni3Sn4 are observed in the couples with Sn-Ag-Cu solder. Electromigration effects are significant, but no Cu diffusion effects upon the solder/Ni reactions are observed.   

[1]   H. B. Huntington in “Diffusion in solids: recent developments”, edited by A. S.Nowich and J. J. Burton, Academic Press, New York, pp. 303-352, (1975).

[2]   C.-M. Chen and S.-W. Chen, 1999, “Electric Current Effects Upon the Sn/Ag Interfacial Reactions”, Journal of Electronic Materials, Vol. 28(7), pp. 902-906.

[3]   S.-W. Chen, C.-M. Chen, and W.-C. Liu, 1998, "The Electric Current Effects Upon the Sn\Cu and Sn\Ni Interfacial Reactions", Journal of Electronic Materials, Vol. 27(11), pp. 1193-1198.
Investigation of Mechanical Stress Distribution in Flexible Microelectronic System Under Bending Force By Finite Element Analysis
Authors: Seo Seung-ho , Lee Jea-Hak , Song Jun-Yeob , Lee Won-Jun
Published: February 2020

The emerging demand on flexible microelectronic systems, such as wearable devices, flexible displays, biomedical and heathcare devices, leads to a continuous reduction of the chip thickness. The ultra-thin chips embedded in a flexible substrate would be deformed or fractured by repeated bending, stretching, or twisting under externally applied mechanical stress. Also, the carrier mobilities in the silicon die depend on mechanical stress during operation, resulting in malfunction of the circuitry. To solve these issues of mechanical and electrical reliability, the device layer of flexible system must be located at the “neutral line”, where the mechanical stress is zero. The mechanical stress of package system in rigid substrates was studied extensively, however, the mechanical stress distribution and the position of neutral line of package system in flexible substrates were rarely reported.

In the present work, we investigated the mechanical stress distribution in flexible microelectronic system under bending force by finite element analysis (FEA). Both the face-down packaging system using flip-chip bonding process and the face-up packaging system using wire bonding process were considered. Three-dimensional finite element models were constructed using different design parameters, and the static analysis was performed assuming elastic deformations of materials. The stress distribution of each component in the packaging systems, the position of the maximum stress and the neutral line were investigated. The effects of design parameters on the position of the neutral line position and the maximum value of von Mises stress were also discussed.

ACKNOWLEDGMENT: This research was supported by “Development of Interconnection System and Process for Flexible Three Dimensional Heterogeneous Devices” funded by MOTIE (Ministry of Trade, Industry and Energy) in Korea

Figure 1. The effect of the silicon die thickness on the mechanical stress distribution of the multilayered structure of silicon die/adhesive/polyimide substrate.

Figure 1
Surface Modification of Lithium Rich NMC for High Rate Lithium Ion Batteries
Authors: Ahn Juhyeon , OH Sihyoung , Kim Jong Hak , Cho Byung Won , Chung Kyung Yun
Published: February 2020

Recently, lithium manganese-rich layered oxides like Li1+xM1-xO2 (M = Ni, Mn, Co) have been extensively scrutinized as one of the most promising cathode materials for the next-generation lithium rechargeable batteries primarily due to their high reversible capacity over 250 mAh/g. These materials are targeted to be potentially utilized in such mid- and/or large- scale applications as electric vehicles (EV) and commercial electricity storage systems (ESS). However, recent studies show that they exhibit a poor electrochemical performance at high power rate and suffer from structural instability in long-term cycling. During the repeated charge and discharge, severe cation mixing and segregations are reported to occur, which causes a series of phase transitions from layered to a defect spinel, and eventually to a rock-salt structure. This phenomenon deteriorates the high-rate performance significantly because it tends to block the diffusion channels for Li+ ions. Herein, we developed a novel surface-modified lithium manganese-rich layered oxide, which shows a substantial improvement in the high-rate performance and long-term cycle life stability. A thin nano-scaled zirconium-doped surface layer was formed on Li1.2Ni0.13Co0.13Mn0.54O2 particle by using potassium nitrate as an additive to guide the crystal habit during the synthetic process. The addition of potassium nitrate is critical in promoting the preferential development of crystal facets open for the diffusion channel. By the low surface barrier driven by the facets growth, zirconium ions could easily enter the lithium octahedral sites within the structure. The Zr-doped surface layer is formed possibly having a cation-disordered rock-salt structure of a few nano-meter scales. This thin surface layer is believed to prevent the adverse phase transitions and cation segregations as well as to shorten the diffusion path for Li+ion within the particle. As a result, the high rate performances are significantly enhanced; a specific capacity at 30 C-rate is observed to be as high as 110 mAh/g and stable performance was obtained for 300 cycles.

Figure. Zr-doped Li1.2Ni0.13Co0.13Mn0.54O2 nanoparticles (a) SEM image, (b) EDS mapping image of Zr-doped surface, (c) Z-contrast STEM-HADDF image taken along the [100] zone axis.

This work is supported by the National Research Foundation of Korea (NRF-2011-0030539).

Figure 1
Three-Dimensional Porous LiFePO4 Cathode Composite Decorated By Nitrogen-Doped Graphene Aerogel for Ultrafast Lithium Storage
Authors: Wang Bo , Liu Tiefeng , Liu Guijing , Wang Lei , Wang Dianlong , Zhao Xiusong
Published: February 2020

Being a candidate of Lithium-ion batteries (LIBs) cathode material, olivine structured LiFePO4 (LFP) has various advantages, however, the major problems associated with LFP still lie in the fact of its poor electric conductivity and low Li+ diffusivity along the [010] direction only[1-2]. Based on this viewpoint, we wrapped (010) facet orientated LFP nanoplatelets (LFP NPs) with N-doped graphene aerogel (N-GA) to prepare a porous N-GA modified LFP composite (LFP@N-GA) through a facile electrostatic attraction treatment combined with a self-assembly process. In such a composite as shown in Figure. 1a-1i, LFP NPs are well surrounded by a N-GA constructed bicontinuous conductive network, which effectively facilitate both Li+and electron transport, and thus, effectively reducing the polarization[3-4].

Electrochemical test results demonstrated that the LFP@N-GA composite electrode indeed exhibited a ultrahigh rate capability (78 mAh·g−1at 100 C) and a stable cyclability (90% capacity retention over 1000 cycles at 10 C), as shown in Figure. 1j and 1k[5-6]. Such a LFP@N-GA cathode material may advance the development of high-power LIB for EVs and HEVs, and the preparation method is independent from the morphology and the synthesis process of the electrochemically active material, and therefore, compatible with many other energy-storage materials for different applications.

Figure 1.Characterization and electrochemical performance of LFP@N-GA composite: (a, b) SEM images at different magnification. (c-h) TEM and HRTEM images. Inset of d: FFT pattern of the HRTEM image, where B denotes the beam direction, indicating the (010) facet orientation. (i) HAADF-STEM image and elemental mapping results of LFP@N-GA. (j) and (k) Rate and cycling performance.

Reference
：

[1]Padhi A. K., Nanjundaswamy K. S., et al., J. Electrochem. Soc., 1997, 144, 1188-1194.

[2]Wang B., Xu B., et al., Nanoscale, 2014, 6 (2): 986-995.

[3]Wang B., Wang Q., et al., RSC Adv., 2013, 3 (43): 20024-20033.

[4]Wang B., Wang S., et al., Mater. Lett., 2014, 118: 137-141.

[5]Wang B., Al A. W., et al., Energy Environ. Sci., 2015, 8 (3): 869-875.

[6]Wang, B.; Wang D., et al., J. Mater. Chem. A, 2013, 1 (1): 135-144.

Figure 1
Structure Deformation and Electronic Spin States Modification in the Surfaces of Charged and Discharged Lithium-Ion Battery Cathodes
Authors: Nakano Hiroshi , Shirasawa Raku , Hattori Shinnosuke , Kunikiyo Toshiyuki , Tokita Yuichi
Published: February 2020

Structures and electronic spin states on active-surfaces for Li-ion (de) intercalation of Lithium Cobalt Oxides (LCO) are investigated by first principle calculation and molecular orbital analysis focusing on differences between charged and discharged states. Instability of the cathodes prevents realizing higher voltage charge of Li-ion Batteries (LIB). Especially, the degradation of the edge surfaces where Li-ions propagate in the charging and discharging processes decreases the capacity of the batteries severely. Despite of the long history of research and development of LIB, the degradation of surfaces of the cathodes has not been known well from electronic states point of view. In this study, by using electronic state calculations and orbitals analyses, we approach the mechanism of the surface deformation, focusing especially on the most probable edge surface of LCO. First, we established the edge surface model in the discharged states and performed the structure optimization with evaluation of the surface formation energy. Second, we deleted three quarters of Li-ions from the surface model and optimized the structure again. Comparison of the both structures shows that Li-ion de-insertion gives the flexibility of the coordination structures of the surface cobalt and promotes the surface structure distortion. Third, the electronic states of the both charged and discharged states were examined. We developed an analysis method of Kohn-sham orbitals which enable us to know the symmetry of the orbitals for valence band minimum and other bands, indicating that we can figure out the surface conditions from the ligand field theory for the surface cobalt and oxygen atoms. Our analyses show that the d-electrons of the surface cobalt atoms in the charged state occupy more unstable orbitals than those in the discharged states. Finally, we concluded that lithium de-intercalation causes surface deformation with unstable cobalt spin states and considered that the deformation brings about further structure degradations. We believe that the results can be applied to the other cathode materials containing transition-metal atoms.
Very-Low Solid-Electrolyte/Electrode Interface Resistance in Li(Ni0.5Mn1.5)O4-Based Thin-Film Lithium Battery
Authors: Shiraki Susumu , Kawasoko Hideyuki , Suzuki Tohru , Shimizu Ryota , Hitosugi Taro
Published: February 2020

All-solid-state lithium batteries with improved safety and larger capacity have been anticipated as a next-generation rechargeable battery. In particular, 5 V-class cathode material, LiNi0.5Mn1.5O4 (LNMO), has received considerable attention for the expected high power density. In all-solid-state LBs using LNMO, however, high interface resistance between an electrode and electrolyte hinders high power density. Thus, the reduction of the interface resistance and the investigation of the origins are of important issues. Recent progress in thin-film deposition techniques of electrodes and electrolytes has made it possible to fabricate all-solid-state thin film batteries with atomically controlled interfaces, and quantitative studies of the interface resistance values have been reported. In this study, we fabricated all-solid-state thin-film lithium batteries using LNMO epitaxial thin films and Li3PO4 solid electrolyte, and demonstrated a very low Li3PO4/LNMO interface resistance.

Figure 1 shows a structure of all-solid-state thin films battery (inset), and its charge and discharge curves. The fabricated thin film batteries consisted of an epitaxial cathode LNMO(100) film, an amorphous solid-electrolyte Li3PO4 film, a metallic anode Li film, a current collector LaNiO3(100) film, and Nb-doped SrTiO3(100) substrate. To ensure a clean Li3PO4/LNMO interface in the thin films batteries, the ultrahigh vacuum chambers used for the film depositions and characterizations were all directly connected each other. The LNMO thin-film battery exhibits good battery performance. The charge and discharge curves show redox reactions of LNMO (Ni2+/Ni4+ and Mn3+/Mn4+), and the capacity did not degrade even up to the 100th cycle.

We also evaluated the interface resistance using impedance spectroscopy, and found a very low interface resistance of ~5 Ωcm2. A Nyquist plot (Fig. 2) displays one semicircle at a higher frequency region (104~106 Hz), originating from the resistance of Li3PO4 (5×10-7 S/cm). In addition, a smaller semicircle at a lower frequency region (102~104 Hz) is attributed to the interface resistance at the Li3PO4/LNMO interface. The very low interface resistance of ~5 Ωcm2 is one order of magnitude smaller than those reported before, and implies that space charge layer formed at the Li3PO4/LNMO interface hardly results in high interface resistance.

This study was supported by NEDO, JST-ALCA, JST-CREST, and Kakenhi. The authors also acknowledge the support of Toyota Motor Corporation.

[1] S. Shiraki, H. Oki, Y. Takagi, T. Suzuki, A. Kumatani, R. Shimizu, M. Haruta, T. Ohsawa, Y. Sato, Y. Ikuhara, T. Hitosugi, J. Power Sources 267 (2014) 881-887.

[2] M. Haruta, S. Shiraki, T. Suzuki, A. Kumatani, T. Ohsawa, Y. Takagi, R. Shimizu, and T. Hitosugi, Nano Lett. 15 (2015) 1498-1502.

Figure 1
What Makes Si Anode Stabilized: Correlation of Electrochemical Performances with Si Local Structural Tranformations
Authors: Ogata Ken , Han Sungsoo , Jeon Seongho
Published: February 2020

Silicon is an alternative anode material for future energy storage devices because it delivers 10 times greater theoretical (>3579 mAh/g) specific capacity than that of a traditional graphite anode (>370 mAh/g). However, Si-based anode materials face significant challenges due to its large volume expansion (~270-300%) upon lithium insertion. This large volume change causes cracking and pulverization of silicon, which leads to loss in electrical contact and drastic capacity fading. In addition, a continuous growth of solid electrolyte interphase (SEI) due to Si cracking causes low Coulombic efficiency, higher resistance to electronic/ionic transport. This will eventually deplete Li resevoir and limit the anode capacity.

To address this challenge, various strategies have been explored through nanostructured material design such as nano/micro-sized Si powders, nano-Si composites, Si nanowires/nanotubes, core-shell type nano/micron Si anodes.1 Despite the significant advances in Si anodes, there still remains critical challenges to overcome, one of the most basic which is poor Coulombic efficiencies (CEs) that unfortunately often remain to be examined. 

Here we studied multiple factors that can lead higher CEs in both half and full cells. We link such electrochemical performance to Si structural transformations in long-term cycles, being probed via a variety of atomistic-level short/long range techniques, such as ex situ nuclear magnetic resonance (NMR),2
ex situ x-ray diffraction (XRD), 3 
ex situ X-ray absorption fine structure (XAFS), and ex situ transmission electron microscopy (TEM). The detail will be presented at the conference.

References

1. Obrovac, M. N. & Krause, L. J. Journal of the Electrochemical Society
154, A103-A108, (2007)

2. Ogata, K. et al.
Nat Commun
5, 3217 (2014).

3. Li, J. & Dahn, J. R. Journal of the Electrochemical Society
154, A156-A161, doi:Doi 10.1149/1.2409862 (2007).