Electrodeposition of Copper for Three-Dimensional Metamaterial

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Electrodeposition of copper for three-dimensional metamaterial fabrication Shendu Yang, Zachary Thacker, Evan Allison, Megan Bennett, Nicholas Cole, and Patrick Pinhero ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b04721 • Publication Date (Web): 24 Oct 2017 Downloaded from http://pubs.acs.org on October 24, 2017

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ACS Applied Materials & Interfaces

Electrodeposition of copper for three-dimensional metamaterial fabrication Shendu Yang, Zachary Thacker, Evan Allison, Megan Bennett, Nicholas Cole, and Patrick J. Pinhero∗ Department of Chemical Engineering, University of Missouri, Columbia, MO 65211, USA E-mail: [email protected] Phone: +1(573)882-7319

Abstract Metamaterials typically consist of metallic and dielectric repeating structures. Electrodeposition of copper is the preferred approach to fabricating the metallic part of the metamaterials of interest in this study. The highly-variant topography requires chemical additives, like chloride ions, 3-mercapto-1-propanesulfonic acid (MPSA), polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) to enhance bottom-up superfilling while maintaining terrace flatness. This study focuses on both experimental and computational investigations of the degradation potential of the additives and their adsorption mechanism in a highly-acidic copper electrolyte in order to optimally parameterize the copper electrodeposition process. Results show Cl-MPSA-PEG-PVP additives perform well, but substitution of PVP with Janus Green B provides better terrace leveling. Additionally, NMR data show a quick and complete conversion of MPSA to bis(3sulfopropyl) disulfide (SPS) in the acidic copper bath. Finally, FEM simulations further show that the accelerator species may initially accumulate and be transported vertically until overplating, whereby they are transported laterally.

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Keywords Electrodeposition, Metamaterial, Additives, Degradation, Copper

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Introduction

Metamaterials (MMs), as a class of artificial material, possessing a physical property to manipulate electromagnetic waves by absorbing, bending, or suppressing waves due to their repeating sub-wavelength features. In the past decade, metamaterials have been demonstrated in almost every technologically relevant spectral range, from radio, 1 microwave, 2 mm-Wave, 3 THz, 4 MIR 5 and NIR 6 to the near optical. 7 In the present study, electrodeposition of Cu was utilized to create MMs and investigated for their potential in an energy harvesting device. This device, seen in Fig. 1, consists of a MM coupled to a rectification nano-antenna (rectenna). The purpose of the MM is to convert thermal energy into surface plasmons that are absorbed and rectified by a rectenna. 8 The spatial dimensions of each functional unit on the device is fabricated relative to the wavelength of EM radiation to be harvested. The target wavelength of the current device was chosen as a compromise between energy density and diode operating efficiency. The efficiency of the current diode design decreases sharply after 1 THz. 9 Besides, the rectenna efficiency is low at high frequencies while the thermal radiation intensity is low at low frequencies. 8 So in this work, the geometry of the device was optimized for operation at 1 THz.

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levelers 16–21 have been used as additives for the electrodeposition of copper. In this work, polyethylene glycol 6000 (PEG) is the carrier and wetting agent. 3-mercaptopropanesulfonic acid (MPSA) is the accelerating agent for acid copper deposition. Among the three additives used in electrodeposition, MPSA is the most unstable because thiols (S-H) oxidize and form disulfides (S-S) in the presence of Cu2+ , 22,23 as shown in chemical reaction 1:

2 MPSA + 2 Cu2+ −−→ SPS + 2 Cu+ + 2 H+

(1)

Levelers are typically molecules having quaternary ammonium cations such as Janus Green B (JGB) 24 and Diazine Black (DB), 19 or having amine functionality, such as polyvinylpyrrolidone (PVP). 25 Levelers also act as secondary suppressers that preferentially adsorb on the peaks of the substrate and inhibit electrodeposition. Some previous work has shown that the best leveling effect of PVP can be obtained when the leveler molecular weight is between 29,000 and 55,000 g/mol. The optimal concentration of PVP is 10 ppm and the leveler dose not strongly impact bottom-up fill. 26 On one hand, since a copper atom has two free electrons at the outermost shell, they can move freely along the lattices when an electric field is applied. The higher the electric field is, the more empty s bands can be formed. Therefore, amines can adsorb onto the substrate, especially on the high current density areas by donating their lone pair electrons to the unoccupied s bands. 27 On the other hand, as the only non-metallic cation with a permanent positive charge, quaternary ammonium can also preferentially adsorb onto the high current density area, the convex area, and block electrodeposition by electrostatic attraction, resulting in a leveling effect on the cathode. In our study, the surface of the samples to be electroplated have tall structures that affect the natural distribution of the electric field. Without additives, the electric field is expected to converge at the top of these structures and diverge at the bottom, as shown in Fig. 1(c). As the substrate is immersed into the electrolyte, PEG adsorbs at the surface forming a monolayer to inhibit the fast and disordered electrodeposition of metal. Because

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most of the metal surface is hydrophobic, PEG is able to wet the cathode surface thoroughly ensuring good contact with the electrolyte. 28,29 The anion of the accelerator additive, MPSA, preferentially locates at areas with the lowest natural current density. In the current study, these areas are the sections of the samples with concave shaped features. As an anion, to the accelerator forms a complex with the copper ion which effectively brings the copper to the lower sections of the features. After electron exchange, copper can be electrodeposited onto the bottom first, causing superfilling of copper to these concave areas. However, overplating above the superfilled area caused by the accumulation of accelerators is commonly observed. To mitigate this effect, a leveler additive is used. The leveler preferentially adsorb to areas with highest current density through amine or quaternary ammonium functionalities, effectively inhibiting deposition and maintaining terrace flatness. For electrodeposition, the most important driving force comes from the external potential which can provide large amounts of electrons to the working electrode and maintain the electrodeposition process. The thickness of deposits can be predicted and calculated by Faraday’s law: ε×I m = n×F MW × t

(2)

where ε is the efficiency, I is the observed current, m is the mass of deposits, n is the number of electrons, F is Faraday’s constant, MW is the molecular weight, and t is the deposition time.

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Experimental Materials and experimental setup

Cupric sulfate pentahydrate (CuSO4 · 5H2 O), sulfuric acid (H2 SO4 ), sodium 3-mercapto-1propanesulfonate (MPSA, NaSO3 (CH2 )3 SH), and hydrochloric acid (HCl) were purchased from Fisher Scientific. Polyethylene glycol (PEG, H(OCH2 CH2 )n OH, MW: 6000), polyvinyl-

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pyrrolidone (PVP, (C6 H9 NO)n , average MW: 40,000) and Janus Green B (JGB, C30 H31 CIN6 ) were purchased from Alfa Aesar. All the experiments were completed using DI water (18.2 MΩ). In our study, the basic bath for the electrolyte consists of 0.25 M CuSO4 and 1.8 M H2 SO4 ; the additives used are HCl, MPSA, PEG, PVP and JGB. Two different kinds of substrates were used as working electrodes for the electrochemical experiment: one is blanket Si/SiO2 wafers and the other is metamaterial substrates containing SU-8 pillars as shown in Fig. 1(b). The Ag/AgCl electrode was used as a reference electrode for all of the measurements. A phosphorous copper anode (purchased from Kocour) was used as counter electrode. All the electrochemical experiments were carried out in a conventional three-electrode cell. In order to make the substrate conductive, all the substrates were thermally evaporated by 20nm Cr as an adhesion layer, followed by a 200 nm copper seed layer. Then, the substrate was masked with nail polish and only 1 cm2 was exposed as the deposition area. This was done because the interface of the substrate between the electrolyte and the air is likely to become corroded, preventing the deposition from continuing. The top conductive area of the wafer was attached by copper tape in order to connect the alligator clip from pontentiostat. The electrodeposition was carried out under the mode of controlled potential coulometry or controlled current mode at room temperature. 400 mL of electrolyte was placed in a beaker with a custom-made 3D-printed cover on the top. There were three holes on the cover, with 2 cm spacing between each hole in case of a big IR drop, also allowing for consistent positioning of the three electrodes for each experiment. No agitation was performed during the experiments.

2.2

i-E characterization

Cyclic voltammetry (CV) experiments were carried out using a Gamry (PCI4/300) potentiostat to examine the relationship between current and potential during electrodeposition and reveals the potential region for reduction and oxidation of different species. 6


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2.3

Surface topography

An optical microscope (Nicolet 0049-005) was used to characterize the topography of the samples received from the electrodeposition process in order to analyze the effects and interplay of additives. An optical profilometer (Vecco NT 9109) was used to measure the surface topography, the RMS surface roughness and to acquire 3D images.

2.4 1

Chemical analysis

H-NMR (300MHz and 600 MHz, Bruker) was used to investigate the chemical structures of

the additives and the changes in their concentrations. The 1 H-NMR samples were prepared via the following steps: 30 (1) 8M KOH solution was used to neutralize the acid solution; (2) pure ethanol was added in a solution:ethanol ratio of 2:3 to precipitate the inorganic compounds; (3) the resulting solution was filtered and evaporated to remove the precipitate; (4) the residue was dissolved in deuterium oxide(D2 O) as the solvent for the NMR measurement.

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the sequence of the reduction reaction is: Cu+ + e- → Cu(s) (first), Cu2+ + 2e- → Cu (s) (second), Cu2+ + e- → Cu+ (third). Since the predominant valence state of Cu in the electrolyte is Cu2+ , the major reduction reaction is Cu2+ + 2e- → Cu(s), whose reduction peak is at -0.37 V. The standard reduction potential for Cu(II)/Cu(0) couple, E0 , is 0.12 V vs Ag/AgCl as shown in Table 1. The onset of Cu reduction on the working electrode begins at 0.06 V, approximately 0.06 V negative of E0 .

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Fig. 3(top) shows that the electrodeposition profiles under different controlled potentials are similar, with each having a gradual increase of current density for the first 0.5 ks, then reaching a steady state current density. In Fig. 3, panel (c) shows a fine, smooth and bright mirror-like copper surface when the applied potential was -0.08 V with a 14 mA/cm2 steady state current density. However, lower or higher voltages give rise to rough and dull copper films. As we know, the cyclic voltammogram (Fig. 2) can provide a general potential and current density range for the electrodeposition of desired species in the electrolyte. The current density during electrodeposition has a large effect on the surface roughness and grain structure of the film. In general, the larger the current density the finer the grain refinement. 31 However, an increase in the current density results in a higher overpotential that increases the nucleation rate, thus resulting in a higher degree of roughness. Therefore, there is an optimal current density for a typical electrodeposition of metal. From panel a to c, the more negative potential, and therefore higher current density, give rise to a finer surface. As the potential and current density is increased further clusters begin to form due to extreme nucleation rates as seen in d to f.

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As other work stated, in a Cl-MPSA-PEG-PVP additive system, MPSA is the most unstable component since in the presence of Cu2+ , thiols (S-H) can be easily oxidized resulting in the formation of disulfides and this process is reversible. 30,32 In the present studies, 1

H-NMR was used to characterize the degradation and the concentration change of the ad-

ditives. As shown in the chemical structures in Fig. 7, both MPSA and SPS have three different kinds of protons with the only difference that SPS is a dimer of MPSA. As shown in Fig. 7 (a), the spectra of MPSA aged in the NMR solvent D2 O for one hour, two days and three days are the same as that of fresh MPSA, having three peaks at 2.07 ppm (M1), 2.71 ppm (M2), and 3.07 ppm (M3), which indicates MPSA is stable at ambient condition in water. Fig. 7(b) is the 1 H-NMR spectra of the powder extracted from fresh and aged solution consisting of MPSA and acid copper bath. It is apparent that all four spectra are the same, which means the compound in the solution remains the same in both fresh and aged solution. Besides, in Fig. 7(b), the chemical shift of the peaks S1 (2.18 ppm), S2 (2.89ppm), and S3 (3.06ppm) agrees with the three characteristic peaks of pure SPS that can be found in the work of others, 30 indicating that MPSA converts to SPS in acid copper solution immediately and SPS would not convert back to MPSA during aging. In contrast with others’ work, the present data shows that this conversion process is not reversible, for which two potential causes are likely. First, it may be caused by different experimental conditions such as low PH and the concentration of copper ions. Second, it should be noted that, the extraction process of MPSA in an acid copper bath involves neutralization, extraction and evaporation; however, this potential cause was ruled out (shown in Section 2 in Supporting Information). So the acid copper bath is likely the reason to drive MPSA to SPS and this process is irreversible in the present experimental conditions.

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the three peaks are 1: 0.63: 0.67 for the fresh electrolyte, and 1: 0.35: 0.36 for the used electrolyte, indicating that the degradation of the accelerators. It is conceivable that in the presence of three more additives, more interactions take place between additives, especially since the accelerators form complexes with copper ions and other additives, which has also been shown by mass spectrometry conducted by other researchers. 23,33 Additionally, there is a single peak at 2.4 ppm which aligns with the characteristic peak of H-C-S, indicating MPSA and SPS would break down into segments during aging and electrodeposition.

3.4

Finite element modeling

Two-dimentional FEM of differing electrodeposition conditions, including variance of the following: aspect ratio of the features, the size of the electrodes, deposition time, and the distance between the cathode and anode, have been investigated. The basic settings can be seen in the previous work. 34,35

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is identical across the horizontal direction as shown in Fig. 9 (c). Besides, seen in Fig. 9 (d) the concentration of the copper ions remains the same as the initial concentration of the bulk electrolyte except that the concentration on the anode is higher than the bulk concentration because the consumable copper anode would lose electrons and generate copper ions while on the cathode the concentration is lower than the bulk due to the reduction of the copper ions to accomplish electrodeposition. The overall concentration on the cathode is uniform except at the edges, which is the reason for the non-uniform electrodeposition profile on the edges.

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source of copper ions. Besides, it is better that the cathode and anode are close to each other to avoid a large IR drop. In order to make the simulation as similar as the real experiment, the length of the cathode was changed to 1 cm, one-third of the anode, and the distance between the two electrodes was changed to 1 cm, as shown in Fig. 10. The profile of three hours electrodeposition of copper dose not show a flat surface and some sharp peaks appear close to the boundaries ( Fig. 10 (b)), but due to the presence of additives, in real electrodeposition the copper film is even across the wafer (shown in Fig. S1 in the Supporting Information). The comparison between the simulation and the experimental results prove again the importance of the additives. The electrolyte potential of electrodeposition of 10 minutes and three hours is shown in Fig. 10 and it is clear that after three hours electrodeposition the potential between the cathode and anode is smaller than that of 10 minutes electrodeposition, which means the overpotential increases with the increase of the electrodeposition time. In addition, the concentration of copper ions in the electrolyte is the same as the original solution while after three hours electrodeposition, the concentration gradient appears and the concentration is highest on the anode while lowest on the cathode.

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30 minutes and the color shows the surface concentration of accelerator. No voids are seen in the trenches indicating the success of superfilling, however, overplating appears above the superfilled area and bumps were formed, which is a common phenomenon for electrodeposition with the addition of accelerators. Besides, the lateral diameter of the bumps decreases as the aspect ratio increases and the concentration of accelerators on the overplated area is higher than that of the flat area, which is caused by the accumulation of accelerators in the trenches during the superfilling process. In addition, from the highest to lowest aspect ratio, the highest concentration area of accelerator that is represented by red color moves from the top to the shoulder of the bumps, which means after overplating takes place, the highest accelerating changes from the vertical direction to the lateral direction.

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Conclusion

A series of experiments was conducted involving the electrodeposition of copper for the fabrication of metamaterials under different conditions. In our work, Cl-MPSA-PEG-PVP additives can interplay with each other well and they are effective in both bottom-up superfill and leveling for electrodeposition of copper for metamaterials. Compared to PVP, another leveler Janus Green B exhibits a better leveling effect. NMR and FTIR data show that even without current flow the accelerator MPSA converts to SPS in acid copper bath immediately and this process is not reversible in our experimental conditions. When there are Cl-MPSA-PEG-PVP four additives in the acid copper solution, accelerators interact with other additives and form complexes resulting in the breakdown of accelerators and the decrease of the concentration; with current flow, this degradation process can be enhanced. We have also successfully conducted a series of 2D COMSOL simulations of electrodeposition and investigated the mechanism of basic electrodeposition, the superfilling of features and adsorption of accelerators. The COMSOL simulation shows that additives are very impor-

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tant to get a uniform and bright deposits and it illustrates that the accelerators accumulate and move vertically in the trench first, after overplating happens, accelerators move along the lateral direction.

Acknowledgement The authors thank RedWave Energy, Inc. and the US DOE-ARPA-E for funding this work. We also wish to thank the MU NMR facility and the MU Center of Nano/Micro Systems and Nanotechnology.

Supporting Information Available Discussion of the degradation of additives; surface topography characterization; resistivity measurement; chemical analysis (1 H-NMR and FTIR) of additives. This material is available free of charge via the Internet at http://pubs.acs.org/.

References (1) Wiltshire, M.; Pendry, J.; Young, I.; Larkman, D.; Gilderdale, D.; Hajnal, J. Microstructured Magnetic Materials for RF Flux Guides in Magnetic Resonance Imaging. Science 2001, 291, 849–851. (2) Smith, D. R.; Kroll, N. Negative Refractive Index in Left-handed Materials. Phys. Rev. Lett. 2000, 85, 2933. (3) Gokkavas, M.; Guven, K.; Bulu, I.; Aydin, K.; Penciu, R.; Kafesaki, M.; Soukoulis, C.; Ozbay, E. Experimental Demonstration of a Left-handed Metamaterial Operating at 100 GHz. Phys. Rev. B 2006, 73, 193103.

25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(4) Yen, T.-J.; Padilla, W.; Fang, N.; Vier, D.; Smith, D.; Pendry, J.; Basov, D.; Zhang, X. Terahertz Magnetic Response from Artificial Materials. Science 2004, 303, 1494–1496. (5) Linden, S.; Enkrich, C.; Wegener, M.; Zhou, J.; Koschny, T.; Soukoulis, C. M. Magnetic Response of Metamaterials at 100 Terahertz. Science 2004, 306, 1351–1353. (6) Zhang, S.; Fan, W.; Panoiu, N.; Malloy, K.; Osgood, R.; Brueck, S. Experimental Demonstration of Near-infrared Negative-index Metamaterials. Phys. Rev. Lett. 2005, 95, 137404. (7) Dolling, G.; Wegener, M.; Soukoulis, C. M.; Linden, S. Negative-index Metamaterial at 780 nm Wavelength. Opt. Lett. 2007, 32, 53–55. (8) Lu, D.; Das, A.; Park, W. Direct Modeling of Near Field Thermal Radiation in a Metamaterial. Opt. Express 2017, 25, 12999–13009. (9) Thacker, Z.; Pinhero, P. J. Terahertz Spectroscopy of Candidate Oxides in MIM Diodes for Terahertz Detection. IEEE Trans. Terahertz Sci. Technol. 2016, 6, 414–419. (10) Liu, Y.; Chen, Y.; Li, J.; Hung, T.-c.; Li, J. Study of Energy Absorption on Solar Cell Using Metamaterials. Sol. Energy 2012, 86, 1586–1599. (11) Lefebvre, M.; Allardyce, G.; Seita, M.; Tsuchida, H.; Kusaka, M.; Hayashi, S. Copper Electroplating Technology for Microvia Filling. Circuit World 2003, 29, 9–14. (12) Kim, S.-K.; Josell, D.; Moffat, T. Electrodeposition of Cu in the PEI-PEG-Cl-SPS Additive System Reduction of Overfill Bump Formation during Superfilling. J. Electrochem. Soc. 2006, 153, C616–C622. (13) Vereecken, P. M.; Binstead, R. A.; Deligianni, H.; Andricacos, P. C. The Chemistry of Additives in Damascene Copper Plating. IBM J. Res. Dev. 2005, 49, 3–18. (14) Kelly, J. J.; West, A. C. Copper Deposition in the Presence of Polyethylene Glycol I. Quartz Crystal Microbalance Study. J. Electrochem. Soc. 1998, 145, 3472–3476. 26


Page 26 of 30

Page 27 of 30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(15) Tan, M.; Guymon, C.; Wheeler, D. R.; Harb, J. N. The Role of SPS, MPSA, and Chloride in Additive Systems for Copper Electrodeposition. J. Electrochem. Soc. 2007, 154, D78–D81. (16) Andricacos, P. C.; Uzoh, C.; Dukovic, J. O.; Horkans, J.; Deligianni, H. Damascene Copper Electroplating for Chip Interconnections. IBM J. Res. Dev. 1998, 42, 567–574. (17) Chang, C.; Lu, X.; Lei, Z.; Wang, Z.; Zhao, C. 2-Mercaptopyridine as a New Leveler for Bottom-up Filling of Micro-vias in Copper Electroplating. Electrochim. Acta 2016, 208, 33–38. (18) Kim, M. J.; Seo, Y.; Kim, H. C.; Lee, Y.; Choe, S.; Kim, Y. G.; Cho, S. K.; Kim, J. J. Galvanostatic Bottom-up Filling of TSV-like Trenches: Choline-based Leveler Containing Two Quaternary Ammoniums. Electrochim. Acta 2015, 163, 174–181. (19) Dow, W.-P.; Li, C.-C.; Su, Y.-C.; Shen, S.-P.; Huang, C.-C.; Lee, C.; Hsu, B.; Hsu, S. Microvia Filling by Copper Electroplating Using Diazine Black as a Leveler. Electrochim. Acta 2009, 54, 5894–5901. (20) Kelly, J. J.; Tian, C.; West, A. C. Leveling and Microstructural Effects of Additives for Copper Electrodeposition. J. Electrochem. Soc. 1999, 146, 2540–2545. (21) Li, Y.-B.; Wang, W.; Li, Y.-L. Adsorption Behavior and Related Mechanism of Janus Green B during Copper Via-filling Process. J. Electrochem. Soc. 2009, 156, D119–D124. (22) Moffat, T.; Baker, B.; Wheeler, D.; Josell, D. Accelerator Aging Effects during Copper Electrodeposition. Electrochem. Solid-State Lett. 2003, 6, C59–C62. (23) Frank, A.; Bard, A. J. The Decomposition of the Sulfonate Additive Sulfopropyl Sulfonate in Acid Copper Electroplating Chemistries. J. Electrochem. Soc. 2003, 150, C244–C250.

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(24) Wang, A.-y.; Chen, B.; Fang, L.; Yu, J.-j.; Wang, L.-m. Influence of Branched Quaternary Ammonium Surfactant Molecules as Levelers for Copper Electroplating From Acidic Sulfate Bath. Electrochim. Acta 2013, 108, 698–706. (25) Willey, M. J.; Reid, J.; West, A. C. Adsorption Kinetics of Polyvinylpyrrolidone during Copper Electrodeposition. Electrochem. Solid-State Lett. 2007, 10, D38–D41. (26) Reid, J. D.; Zhou, J. Impact of Leveler Molecular Weight and Concentration on Damascene Copper Electroplating. ECS Trans. 2007, 2, 77–92. (27) Zhao, L.-B.; Huang, R.; Bai, M.-X.; Wu, D.-Y.; Tian, Z.-Q. Effect of Aromatic AmineMetal Interaction on Surface Vibrational Raman Spectroscopy of Adsorbed Molecules Investigated by Density Functional Theory. J. Phys. Chem. C 2011, 115, 4174–4183. (28) Chang, S.-C.; Shieh, J.-M.; Lin, K.-C.; Dai, B.-T.; Wang, T.-C.; Chen, C.-F.; Feng, M.S.; Li, Y.-H.; Lu, C.-P. Wetting Effect on Gap Filling Submicron Damascene by an Electrolyte Free of Levelers. J. Vac. Sci. Technol., B: Microelectron. Nanometer Struct.– Process., Meas., Phenom. 2002, 20, 1311–1316. (29) Dow, W.-P.; Yen, M.-Y.; Lin, W.-B.; Ho, S.-W. Influence of Molecular Weight of Polyethylene Glycol on Microvia Filling by Copper Electroplating. J. Electrochem. Soc. 2005, 152, C769–C775. (30) Choe, S.; Kim, M. J.; Kim, H. C.; Cho, S. K.; Ahn, S. H.; Kim, S.-K.; Kim, J. J. Degradation of Bis (3-sulfopropyl) Disulfide and its Influence on Copper Electrodeposition for Feature Filling. J. Electrochem. Soc. 2013, 160, D3179–D3185. (31) Rashidi, A.; Amadeh, A. The Effect of Current Density on the Grain Size of Electrodeposited Nanocrystalline Nickel Coatings. Surface and Coatings Technology 2008, 202, 3772–3776.

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(32) Moçotéguy, P.; Gabrielli, C.; Perrot, H.; Zdunek, A.; Sanz, D. N. Influence of the Anode and the Accelerator on Copper Bath Aging in the Damascene Process. J. Electrochem. Soc. 2006, 153, G1086–G1098. (33) Lee, W.-H.; Hung, C.-C.; Chang, S.-C.; Wang, Y.-L. Bis-(3-sodiumsulfopropyl disulfide) Decomposition with Cathodic Current Flowing in a Copper-electroplating Bath. J. Electrochem. Soc. 2010, 157, H131–H135. R (34) Copper Deposition in a Trench. COMSOL Multiphysics v. 5.0. COMSOL AB, Stock-

holm, Sweden. 2015. R v. 5.0. COMSOL AB, Stock(35) Superfilling Electrodeposition. COMSOL Multiphysics

holm, Sweden. 2015.

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Electrodeposition of Copper for Three-Dimensional Metamaterial

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