SEIRAS Study of Chloride-Mediated Polyether Adsorption on Cu

Liu, Guokun; Zou, Shouzhong; Josell, Daniel; Richter, Lee J.; Moffat, Thomas P.

doi:10.1021/acs.jpcc.8b06644

Cited by 58 publications

(85 citation statements)

References 113 publications

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“…1 – 8 Halide adsorption by itself leads to acceleration of the copper deposition rate while polyether co-adsorption on the halide adlayer gives rise to significant inhibition of copper deposition by limiting access of Cu 2+ aq to the metal surface. 1 – 26 Electroanalytical, 1 – 26 gravimetric microbalance, 14 , 15 ellipsometry 18 and vibrational spectroscopy 27 , 28 studies unambiguously demonstrate that halide adsorption is required for co-adsorption of an effective polyether suppressor layer. Co-adsorption involves factors from the multiplicity of halide-polyether binding sites, 24 to halide perturbation of interface water structure that makes it more hydrophobic favoring polyether adsorption, 28 to a possible role of Cu + as an ether-halide binding agent.…”

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confidence: 92%

“…1 – 26 Electroanalytical, 1 – 26 gravimetric microbalance, 14 , 15 ellipsometry 18 and vibrational spectroscopy 27 , 28 studies unambiguously demonstrate that halide adsorption is required for co-adsorption of an effective polyether suppressor layer. Co-adsorption involves factors from the multiplicity of halide-polyether binding sites, 24 to halide perturbation of interface water structure that makes it more hydrophobic favoring polyether adsorption, 28 to a possible role of Cu + as an ether-halide binding agent. 9 , 11 , 27 Upon polarization to negative potentials the inhibition breaks down and the electrode bifurcates into active plating versus passive regions that subsequently yields significant voltammetric hysteresis.…”

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confidence: 92%

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Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias

Braun

Josell

Silva

et al. 2019

J. Electrochem. Soc.

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101

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Bottom-up Cu deposition in metallized through silicon vias (TSV) depends on a co-adsorbed polyether–Cl − suppressor layer that selectively breaks down within recessed surface features. This work explores Cu deposition when formation of the suppressor blocking layer is limited by the flux of Cl − . This constraint leads to a transition from passive surfaces to active deposition partway down the via sidewall due to coupling between suppressor formation and breakdown as well as surface topography. The impact of Cl − concentration and hydrodynamics on the formation of the suppressor surface phase and its potential-dependent breakdown is examined. The onset of suppression breakdown is related to the local Cl − coverage as determined by the adsorption isotherm or transport limited flux. A two-additive co-adsorption model is presented that correlates the voltammetric potential of suppression breakdown with the depth of the passive-active transition during TSV filling under conditions of transport limited flux and incorporation of Cl − . The utility of potential waveforms to optimize the feature filling process is demonstrated. At higher Cl − concentrations (≥80 μmol/L), sidewall breakdown during Cu deposition occurs near the bottom of the via followed by a shift to bottom-up growth like that seen at higher Cl − concentrations.

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confidence: 92%

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confidence: 92%

Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias

Braun

Josell

Silva

et al. 2019

J. Electrochem. Soc.

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101

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“…For low Cl − concentration, suppression breakdown is determined by flux limitation on the Cl − whose co-adsorption is required to form the blocking polyether-Cl − suppressor phase. 13 The transition from passivated surface to active deposition is localized at fixed depth in the TSV that reflects the balance point between the concentration- and transport-dependent rate of halide adsorption onto the surface and the potential-dependent rate of its removal by consumption. 12 This is congruent with previous S-NDR bifurcation models of feature filling that capture discontinuous deposition within features due to gradients in additive and metal ion concentration that translate to potential-dependent depth of suppression breakdown.…”

Section: Discussionmentioning

confidence: 99%

“…Among the systems examined are electrolytes containing poloxamine and chloride that co-adsorb to form the suppressor layer that underlies bottom-up Cu filling of 56 μm deep annular TSV. 4 , 13 Feature filling based on this additive system has been explored over a broad range of deposition conditions in electrolytes containing 1 mmol/L Cl − and 20 μmol/L to 80 μmol/L poloxamine 11 (variable polyether and fixed high Cl − ) as well as electrolytes containing 20 μmol/L to 80 μmol/L Cl − and 40 μmol/L poloxamine (fixed polyether and variable low Cl − ). 12 A single additive S-NDR model, based on disruption of the passivating polyether by metal deposition with the kinetic parameters obtained from electroanalytical measurements under well-defined hydrodynamics, captures the experimental TSV filling in the high-Cl − electrolytes for a range of micromolar polyether concentrations.…”

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confidence: 99%

Bottom-Up Copper Filling of Millimeter Size Through Silicon Vias

Josell

Menk

Hollowell

et al. 2019

J. Electrochem. Soc.

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This work demonstrates void-free Cu filling of millimeter size Through Silicon Vias (mm-TSV) in an acid copper sulfate electrolyte using a combination of a poloxamine suppressor and chloride, analogous to previous work filling TSV that were an order of magnitude smaller in size. For high chloride concentration (i.e., 1 mmol/L) bottom-up deposition is demonstrated with the growth front being convex in shape. Instabilities in filling profile arise as the growth front approaches the free-surface due to coupling with electrolyte non-uniform hydrodynamics. The reentrant notches at the bottom of the TSVs caused by intentional over-etching during fabrication negatively impact the filling results. In contrast, deposition from low chloride electrolytes (i.e., 80 μmol/L) proceeds with a passive-active transition on the via sidewalls. For a given applied potential the location of the transition is fixed in time and the growth front is concave in nature reflecting the gradient in chloride surface coverage. Application of a suitable potential wave form enables the location of the sidewall transition to be systematically advanced thereby giving rise to void-free filling of the TSV.

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“…Increasing ratio of gauche conformers upon adsorption was consistent with experimental and theoretical studies of PEG adsorption, which indicated a reorientation from predominantly trans conformations in solution to gauche. [25,28,29] Similar to the previous studies, we used surface-enhanced Raman spectroscopy (SERS) for conformational analysis of PEI on the chloridecovered Cu surface (Figure 6). Peaks a and b are assigned to symmetric and asymmetric CH 2 stretching modes.…”

Section: Structural Analysis On the Surfacementioning

confidence: 99%

The Adsorption Structure of Polyethylene Imine on Copper Surfaces for Electrodeposition

Schmidt

Bandas

Gewirth

et al. 2021

Physica Rapid Research Ltrs

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Electrodeposition of copper constitutes a key process for fabrication of modern microelectronic devices. [1][2][3][4] Commonly, the deposition process is required to fill recessed structures with metal. The size scales of such recessed structures range from nanometer-sized dual damascene structures for production of microprocessors, [5,6] to micrometer-sized through-silicon vias (TSVs) for 3D integration of different components within a package. [7,8] Despite the huge differences with regard to the dimensions, the various filling applications share the requirement of different local deposition rates to fill the recessed structures with copper. In order for filling to occur, the deposition needs to be accelerated at the bottom of the features, whereas it should be suppressed at the top. [9][10][11][12][13] These differential deposition rates may be obtained by the addition of suitable organic additives to the electrolyte. [1,6,[9][10][11][12][13][14][15] Electrolytes for electrolytic copper deposition typically consist of a cupric ion source, sulfuric acid, and halides such as chloride. Deposition of metallic copper from cupric ions is generally accepted to take place via cuprous ion intermediates. [6,[16][17][18] Industrially relevant plating electrolytes further contain a set of typically three organic additives, which provide the differential deposition rates to allow feature filling. [1,6,[9][10][11][12][13][14][15] Local acceleration of copper electrodeposition at the feature bottom is achieved by the accelerator and inhibition at the feature top by the suppressor. [10,11,13,14,19,20] The leveler further supports filling by local inhibition at exposed areas and may, thereby, prevent mounding over the recessed features. [14,21] Leveler additives typically consist of (poly) cationic alkylamines, e.g., PEI, which are supposed to interact with the surface by hydrophobic and interfacial anion/cation pairing effects. [15,21,22] Previous and recent spectroelectrochemistry investigations further supported interaction of this class of molecules to surface-confined halides. [23,24] An additional contribution to the adsorption by the formation of insoluble complexes with cuprous ions was proposed. [22] However, no direct evidence for interaction of the hydrophobic alkyl moieties with the bare or halide-covered copper surface, electrostatic interactions between halide anions and cationic ammonium ions, or complex formation with cuprous ions is available. Furthermore, the exact mechanism of the inhibition of the deposition is unclear and has been ascribed to the formation of a physical barrier for cupric ions by either adsorption or precipitation. [15,21,22] Recently, computational modeling and comparison of the results with electrochemical and spectroelectrochemical data was shown to be a suitable approach to reveal the detailed mechanism of the adsorption and inhibition of polyethylene glycol (PEG)-based suppressors. [25] Here, we use this approach to address PEI, which serves as reference compound for leveler additives...

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SEIRAS Study of Chloride-Mediated Polyether Adsorption on Cu

Cited by 58 publications

References 113 publications

Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias

Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias

Bottom-Up Copper Filling of Millimeter Size Through Silicon Vias

The Adsorption Structure of Polyethylene Imine on Copper Surfaces for Electrodeposition

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