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

Abstract

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.

Nano-Plasticity of an Electrified Ionic Liquid/Electrode Interface: Uncovering Hard–Soft Structuring via Controlled Metal Fill Factor

“…The IREs used in this work were micromachined Si substrates fabricated from ∼0.5 mm thick, standard Si wafers, diced into approximately 1 cm × 1 cm chips. The low path length through these Si IREs is advantageous when working below ∼1400 cm –1 and gives rise to so-called wide-frequency ATR–SEIRAS , and have convenient dimensions for physical deposition of conductive films. The majority of IREs in this work were first coated with a 15 nm thick film of ITO using a home-built RF magnetron sputtering unit at a base vacuum of 2 × 1 × 10 –5 Torr.…”

Revisiting the Polyethylene Glycol-Chloride Adsorption Structure on Cu Electrode in Sulfuric Acid Solution by Wide-Frequency ATR-SEIRAS

“…55°) served as the working electrode for in situ ATR-SEIRAS (for metal film preparation details, see the Supporting Information). − A Pt mesh and a Hg/Hg 2 SO 4 /K 2 SO 4(sat’d) (MSE) served the counter electrode and the reference electrode, respectively, and a thin slice of glass sand core was placed between the chambers of the working electrode and the counter electrode. Aliquots of a concentrated PEG or HCl solution were injected into the catholyte chamber under strong N 2 bubbling to attain the desired concentration.…”

“…In this work, the microscopic structure of the PEG-Cl – inhibition layer is further clarified by wide-frequency ATR-SEIRAS in conjunction with electrochemical quartz crystal microbalance (EQCM) measurement. In situ wide-frequency ATR-SEIRAS is able to detect the frequency range above 650 cm –1 while conventional ATR-SEIRAS can only detect above 1000 cm –1 , − providing richer spectral information to update the PEG-Cl – inhibition layer structure, and EQCM provides additional evidence in support of PEG on the underlying Cl – adstructure. Detailed analysis of time-evolved spectral features for C–O, C–H, and O–H vibration modes allows direct dynamic observation of PEG conformation change upon its adsorption on the underlying Cl – adlayer on the Cu electrode in response to the hydrophobic interaction between subunits of PEG and the Cl – adlayer.…”

Uncovering the Dissociative Adsorption of the Leveler Janus Green B on Cu Electrodes at the Molecular Level

“…Owing to insufficient surface sensitivity and narrow frequency-detection range as well as the complication from additional Cu 2+ , the interfacial adsorption configuration of JGB at Cu electrodes was not well established then without in situ spectral evidence of two fragments. Recently, wide frequency attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), meriting a high surface sensitivity and an extended wavenumber detection range to the fingerprint region, − has been applied in studying adsorption structures of the accelerator SPS and the suppressor PEG at Cu electrodes. , This upgraded technique is expected to provide direct molecular insight into the adsorption structure of the leveler JGB at Cu electrodes.…”