Study of anodic layers and their effects on electropolishing of bulk and electroplated films of copper

Huo, J.; Solanki, R.; McAndrew, James

doi:10.1023/b:jach.0000015621.31360.14

Cited by 38 publications

(33 citation statements)

References 16 publications

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“…The space between features (i.e., the pattern pitch) was found to be less important, but for a given feature width, the degree of planarization was found to decrease with increasing spacing. Huo et al [16] have recently published an interesting study of electrochemical planarization using four phosphoric-acid-based electrolytes and a 70-wt.% hydroxyethylidenediphosphoric acid (HEDP) electrolyte. They studied electropolishing mechanisms using electrochemical impedance spectroscopy and concluded that in the phosphoric acid electrolyte an acceptor mechanism, discussed in the next section, is probably the best explanation for the limiting-current plateau, in contradiction of the assertions of Chang et al They concluded that a salt-film mechanism prevails for the HEDP electrolyte.…”

Section: Recent Workmentioning

confidence: 99%

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Electrochemical planarization of interconnect metallization

2005

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Section: Recent Workmentioning

confidence: 99%

“…Alternative metal-removal methods should enable high dissolution rates without subjecting the substrate to excessively large pressures. Electrochemical dissolution methods, either as a CMP replacement or a complement to CMP, have received a fair amount of recent attention [8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical planarization of interconnect metallization

2005

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“…There are two EP mechanisms of Cu and Cu alloys. One is the salt-film mechanism [4,6,14] and the other is the acceptor mechanism [15][16][17]. According to the former mechanism, a salt film with saturated metal ions is developed on the anode surface during the EP process.…”

Section: Introductionmentioning

confidence: 99%

Electropolishing Behaviour of 73 Brass in a 70 vol % H3PO4 Solution by Using a Rotating Cylinder Electrode (RCE)

Huang

Chen

Sun

2017

Metals

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Abstract:The electropolishing behaviour of 73 brass was studied by means of a rotating cylinder electrode (RCE) in a 70 vol % H 3 PO 4 solution at 27 • C. Owing to the formation of a blue Cu 2+ -rich layer on the brass-RCE, an obvious transition peak was detected from kinetic-to diffusion-controlled dissolution in the anodic polarisation curve. Electropolishing was conducted at the potentials located at the transition peak, the start, the middle, and the end positions in the limiting-current plateau corresponding to the anodic polarisation curve of the brass-RCE. A well-polished surface can be obtained after potentiostatic electropolishing at the middle position in the limiting-current plateau. During potentiostatic etching in the limiting-current plateau, a blue Cu 2+ -rich layer was formed on the brass-RCE, reducing its anodic dissolution rate and obtaining a levelled and brightened brass-RCE. Moreover, a rod climbing phenomenon of the blue Cu 2+ -rich layer was observed on the rotating brass-RCE. This enhances the coverage of the Cu 2+ -rich layer on the brass-RCE and improves its electropolishing effect obviously.

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“…In certain systems, the chemical complexation of metal ions with the electrolyte and water molecules will support phase separation and the formation of a viscous liquid phase (viscous layer) adjacent to the anode. [2][3][4][5][6][7][8] The layer of viscous liquid serves as a barrier to the diffusion of ions from the surface of the anode and vice-versa, thereby reducing the efficiency of the electropolishing process. The density of the viscous liquid is assumed to be similar to the density of the electrolyte solution.…”

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Editors' Choice—The Enhancement of Ion Transport in an Electrochemical Cell Using High Frequency Vibration for the Electropolishing of Copper

Dubrovski

Tietze

Zigelman

et al. 2018

J. Electrochem. Soc.

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A previous experiment showed that the rate of the electropolishing of a copper anode may be increased by twofold when generating a 60 KHz to 1.7 MHz frequency vibration in the anode. In this work we use theory to elucidate the mechanisms by which the vibration may enhance the transport of ions in the electrolyte solution and support the formation of dents in the anode, which was observed in experiment. We find that in the limit of weak ion convection the transport of ions mainly supports the formation of dents in the anode. However, in the limit of prominent ion convection we find an appreciable contribution of the vibration to the efficiency of the electropolishing process, in accordance with the previous experimental findings. The contribution of the vibration to ion transport is given by 2 √ PeDkC s /π √ π, in which the Peclét number, Pe, quantifies the ratio between the convective and diffusive fluxes of ions, and D, k, and C s are the diffusion coefficient of the ions, the wavenumber of the vibration, and the solubility limit of the ions in the electrolyte. Electropolishing is a well-known technique used to polish metal surfaces by employing electrochemistry.1 The most basic electropolishing system is a classic electrochemical cell, comprising an anode and a cathode in an electrolyte solution, as depicted in Fig. 1. The application of an electrical potential difference between the electrodes will decompose the surface of the anode -the metallic object to be polished -to metal ions that dissolve in the electrolyte solution. Sharp corners on the metal anode dissolve to ions faster than flat areas. Hence, the electropolishing process renders the surface of the anode smooth. In certain systems, the chemical complexation of metal ions with the electrolyte and water molecules will support phase separation and the formation of a viscous liquid phase (viscous layer) adjacent to the anode.2-8 The layer of viscous liquid serves as a barrier to the diffusion of ions from the surface of the anode and vice-versa, thereby reducing the efficiency of the electropolishing process. The density of the viscous liquid is assumed to be similar to the density of the electrolyte solution.It was previously found that exciting a high frequency (60-1700 KHz) mechanical vibration in the anode may enhance the efficiency of the electropolishing process by two-fold. 9,10 However, it appears that the vibration further supports the formation of dents on the surface of the anode. The experimental system investigated previously is depicted in Fig. 1. It is an electrochemical cell, which is comprised of copper electrodes, a power supply, and an electrolyte solution containing water, concentrated phosphoric acid, and isopropyl alcohol. A piezoelectric transducer generates vibration in the anode. Upon the application of an electrical potential difference between the electrodes, which initiates the electropolishing process, a viscous layer of a thickness of about 1-2 mm forms adjacent to the electrode, as depicted in Fig. 2. The viscous layer is...

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Study of anodic layers and their effects on electropolishing of bulk and electroplated films of copper

Cited by 38 publications

References 16 publications

Electrochemical planarization of interconnect metallization

Electrochemical planarization of interconnect metallization

Electropolishing Behaviour of 73 Brass in a 70 vol % H3PO4 Solution by Using a Rotating Cylinder Electrode (RCE)

Editors' Choice—The Enhancement of Ion Transport in an Electrochemical Cell Using High Frequency Vibration for the Electropolishing of Copper

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