Energetics and dynamics of Cu(001)-c(2×2)Cl steps

Dijk, Frank R. van; Zandvliet, Henricus J.W.; Poelsema, Bene

doi:10.1063/1.2203412

Cited by 2 publications

(4 citation statements)

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“…A solid-on-solid model indicates that step faceting may be ascribed to strong repulsive dipole interactions between next-nearest-neighbor Cl − species that stabilizes the underlying kink-saturated metal steps. 35 In support of this model, theoretical consideration, 62 along with a recent X-ray study, indicates that Cl − remains largely ionic in the absorbed state. 34 Cyclic voltammetry of Cu͑100͒ in 0.01 mol/L HClO 4 with 0.001 mol/L KCl, shown in Fig.…”

Section: Resultsmentioning

confidence: 85%

“…The energetics of Cl − -induced step faceting on Cu͑100͒ have been explained in terms of a strongly repulsive interaction between nearest-neighbor anions in the c͑2 ϫ 2͒ adlayer. 35 In Cu superfilling, PEG additions to a Cl − containing electrolyte lead to inhibition of the metal deposition rate that approaches 2 orders of magnitude relative to that in the base CuSO 4 solution. 4,20,[36][37][38][39][40] Inhibition is associated with adsorption of a thin layer ͑ϳ6 nm͒ of PEG on top of the Cl − adlayer.…”

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confidence: 99%

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Accelerator Surface Phase Associated with Superconformal Cu Electrodeposition

Moffat

Liu

2010

J. Electrochem. Soc.

132

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Superconformal film growth is a key process in state-of-the-art Cu metallization of electronic devices. Superfilling of recessed surface features results from the competition between electrolyte additives that accelerate or inhibit Cu electroplating. In situ scanning tunneling microscopy is used to image the accelerating bis-͑3-sodiumsulfopropyl disulfide͒ ͑SPS͒-Cl − surfactant phase that is responsible for disrupting and preventing the formation of the inhibiting poly͑ethylene glycol͒-Cl − layer. Various aspects of competitive and coadsorption of Cl − and SPS on Cu͑100͒ were examined for industrially relevant additive concentrations. At potentials associated with superfilling, a saturated, c͑2 ϫ 2͒ Cl − ordered adlayer forms on the surface. When as-received SPS is added, individual SPS and ͑3-mercaptopropyl͒sulfonate ͑MPS͒ molecules are imaged as a mobile two-dimensional gas diffusing on the Cl − adlattice. The SPS-Cl − surfactant accounts for many aspects of the additive function previously observed and stipulated by the curvature enhanced accelerator model of superconformal film growth. SPS-derived species of differing mobility and tunneling contrast appear with exposure time. The lattice gas species are sensitive to the imaging conditions with tip-molecule interactions particularly evident at higher tunneling currents. At negative potentials, the c͑2 ϫ 2͒ Cl − adlayer is disrupted by an order-disorder transition, followed by desorption at more negative potentials. This allows direct access of SPS to the Cu metal whereupon irreversible sulfide formation occurs.In the past decade, Cu electrodeposition has become the dominant technology for fabricating interconnects for microelectronic devices over length scales ranging from those of damascene processing of submicrometer logic and memory circuitry to through silicon vias ͑TSVs͒ for chip stacking and circuit board metallization. 1 Central to the success of this technology is its ability to generate voidand seam-free bottom-up filling of trenches and vias by additive derived superconformal growth. 2 The desired bottom-up superconformal growth mode derives from a competition between rateaccelerating and rate-inhibiting two-dimensional ͑2D͒ phases for the available surface area within filling features. Area change is a key aspect that accompanies deposition on any nonplanar interface. 3,4 Feature filling behavior is well described by a mass balance construct known as the curvature enhanced adsorbate coverage ͑CEAC͒ model. 3,4 In this model, the coverage of the more strongly bound accelerator surface phase increases during area reduction accompanying deposition within recessed features, thereby giving rise to the bottom-up superfilling dynamic. For a prototypical acid CuSO 4 electrolyte, the suppressing or inhibiting phase involves coadsorption of chloride with polyether, whereas the accelerating phase derives from the combination of chloride with either a sulfonate-terminated disulfide or thiol. The most widely discussed additive system to date is chloride ͑Cl − ͒, ...

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Section: Resultsmentioning

confidence: 85%

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confidence: 99%

Accelerator Surface Phase Associated with Superconformal Cu Electrodeposition

Moffat

Liu

2010

J. Electrochem. Soc.

132

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“…While the atomic positions of the clean surface are clearly defined, the occupancy and site geometry of halide atoms at step edges is more challenging to determine. In many models Cl – is assumed to occupy the 4-fold hollow sites with little distortion at the step. − , In two other studies, occupancy of 3-fold sites was considered for the S 2 out-of phase steps. , However, this assignment was quickly dismissed in the electrochemical study in favor of a 4-fold site based on image analysis . When compared against these step structures, our DFT calculations found the structures S 2 and S 2 ′ in Figure b to have more favorable step formation energies.…”

Section: Resultsmentioning

confidence: 96%

“…In many models Cl − is assumed to occupy the 4-fold hollow sites with little distortion at the step. [8][9][10][11][12][13][14][15]51 In two other studies, occupancy of 3-fold sites was considered for the S 2 out-of phase steps. 12,15 However, this assignment was quickly dismissed in the electrochemical study in favor of a 4-fold site based on image analysis.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Halide-Induced Step Faceting and Dissolution Energetics from Atomistic Machine Learned Potentials on Cu(100)

2020

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Adsorbates impact the surface stability and reactivity of metallic electrodes, affecting the corrosion, dissolution, and deposition behavior. Here, we use density functional theory (DFT) and DFT-based Behler−Parrinello neural networks (BPNN) to investigate the geometry, surface formation energy, and atom removal energy of stepped and kinked surfaces vicinal to Cu(100) with a c(2 × 2) Cl adlayer.DFT calculations indicate that the stable structures for the adsorbate-free vicinal surfaces favor steps with ⟨110⟩ orientation, while the addition of a c(2 × 2) Cl adlayer leads to ⟨100⟩ step faceting, in agreement with scanning tunneling microscopy (STM) observations. The BPNN calculations produce energies in good agreement with DFT results (root-mean-square error of 1.3 meV/atom for a randomly chosen set of structures excluded from the training set). We draw three conclusions from the BPNN calculations. First, Cl on the upper ⟨100⟩ step edges occupies the 3-fold hollow sites (as opposed to the 4-fold sites on the terraces), congruent with deviations of the STM height profile for the adsorbate at the upper step edge. Second, disruptions in the continuity of the halide overlayer at the steps result in significant long-range step−step interactions. Third, anisotropic metal dissolution and deposition energetics arise from phase shifts of the c(2 × 2) adlayer at orthogonal ⟨100⟩ steps. This DFT-BPNN approach offers an effective strategy for tackling large-scale surface structure challenges with atomic-level accuracy.

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Energetics and dynamics of Cu(001)-c(2×2)Cl steps

Cited by 2 publications

References 15 publications

Accelerator Surface Phase Associated with Superconformal Cu Electrodeposition

Accelerator Surface Phase Associated with Superconformal Cu Electrodeposition

Halide-Induced Step Faceting and Dissolution Energetics from Atomistic Machine Learned Potentials on Cu(100)

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