Interfacial Leveler-Accelerator Interactions in Cu Electrodeposition

Bandas, Christopher D.; Rooney, Ryan T.; Kirbs, A.; Jäger, Cornelia; Schmidt, Ralf; Gewirth, Andrew A.

doi:10.1149/1945-7111/abee5d

Cited by 34 publications

(27 citation statements)

References 50 publications

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“…The interaction of PEI with surface-confined chloride is also supported by recent spectroelectrochemistry investigations. [24] As Figure 4 shows, the same trend is evident in the presence of cuprous ions. A striking difference between the protonation states is visible in the proportions of PEI found in the electrolyte region.…”

Section: Structural Analysis On the Surfacesupporting

confidence: 56%

“…[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.…”

mentioning

confidence: 99%

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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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Section: Structural Analysis On the Surfacesupporting

confidence: 56%

mentioning

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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“…In principle, in situ vibrational spectroscopies including Raman, − infrared (IR), , and sum-frequency generation (SFG) spectroscopies are able to provide the structural information on adsorbates on Cu electrodes. Among these in situ techniques, SFG merits a unique interfacial specificity, but it depends upon high-performance laser and well-trained professionals with the detectable frequencies limited usually to more than 1000 cm –1 .…”

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confidence: 99%

“…In addition, electrochemical SFG results are often too complicated to be explained. Electrochemical surface-enhanced Raman spectroscopy (SERS) merits the low-frequency detection with high surface sensitivity, and it has been used most widely for characterizing the adsorption configurations of additives on a Cu surface. − Nevertheless, the oxidation–reduction cycling (ORC) pretreatment of Cu in a chloride-containing solution for the SERS effect may complicate the surface structure and composition . In addition, the local high power density of laser irradiation may cause an unwanted photochemical reaction.…”

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confidence: 99%

“…In situ SERS measurement requires the ORC pretreatment of a Cu electrode in KCl solution. Based on previous SERS spectral results, mixed trans and gauche modes of MPS-thiolate were assumed on Cu electrode. , In the gauche mode, the sulfonate group was assumed closer to the Cu surface, in favor of accelerating the deposition of copper. Nevertheless, the above ORC pretreatment involves the dissolution and redeposition of Cu atoms in KCl solution, and the resulting SERS-active Cu electrode contains lots of complex surface defects and clusters, which are likely responsible for partial conversion of MPS-thiolate from trans mode to gauche mode; thus, the structural information about MPS-thiolate on Cu electrode may be distorted with an in situ SERS measurement.…”

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In Situ Wide-Frequency Surface-Enhanced Infrared Absorption Spectroscopy Enables One to Decipher the Interfacial Structure of a Cu Plating Additive

Mao

et al. 2022

J. Phys. Chem. Lett.

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In situ spectroscopic characterization of the interfacial structure of an organic additive at a Cu electrode is essential for a mechanistic understanding of Cu superfilling at the molecular level. In this work, we demonstrate wide-frequency attenuated total reflection surface-enhanced infrared absorption spectroscopy (wf-ATR-SEIRAS) to elucidate the dissociative adsorption of bis(sodium sulfopropyl)-disulfide (a typical accelerator) on a Cu electrode in conjunction with the electrochemical quartz crystal microbalance measurement and modeling calculations. The wf-ATR-SEIRAS clearly identifies the peaks featuring the sulfonate and methylene groups as well as the C–Ssulfonate and C–Sthiol vibrations of the adsorbate. Analysis of relative peak intensities from 1100 to 650 cm–1 reveals a more tilted alkyl chain axis for the thiolate on Cu than that on Au, which is supported by comparative density functional theory calculations. This work opens a new avenue for the wf-ATR-SEIRAS to study interfacial structures of electroplating additives related to advanced microelectronics manufacture.

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