Adsorption Behavior of TBPS in the Process of Cu Electrodeposition on an Au Film

Abstract

The adsorption behavior of an Cu electroplating additive, 3,3 thiobis-(1-propanesulfonic acid sodium salt) (TBPS) in a process of Cu deposition onto a single crystalline Au(111) surface is studied by an in-situ Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS). The SEIRAS spectra of the TBPS adlayer on a Cu film is investigated first and compared to that on an Au film. These results are utilized to evaluate the characteristics of TBPS adlayer on the electrode surface during the Cu deposition and stripping processes. The results show that the SEIRAS spectra of TBPS adsorbed on the Cu film resembles closely to that on the Au film, and the most pronounced peaks are symmetric S-O (ss-SO) and asymmetric S-O (as-SO) stretching modes. However, the as-SO band is sharper with a higher intensity on the Cu film. Since the ss-SO and as-SO peaks correspond to the molecular with upright and lie-down orientations, respectively, it implies that the TBPS molecules have higher ratio of lie-down orientation on the Cu film. In the Cu electrodeposition process, the cyclic voltammetry (CV) result shows that the presence of the TBPS in the HClO solution can decrease the inhibition effect of HClO to the Cu deposition. For the spectra measured at various potential during cathodic and anodic sweeping, an obvious change of the spectra occurs at ca. 0.6 V, the initiation of Cu underpotential deposition (Cu-UPD). For potentials higher and lower than 0.6 V, the spectra are similar, respectively, to those measured for the Au and Cu films. This result indicates that the TBPS molecules originally adsorbing on the Au film transfer to the surface of deposited Cu layer. This inference is also confirmed by the variation in wavenumber and peak intensity of ss-SO and as-SO peaks during the potential sweeping.

Novel Additives in Copper Electrorefining—Small Laboratory Scale

“…Researchers around the world are continuously seeking innovative organic substances that can act as inhibitors in the electrorefining process. A wide range of studies are being conducted on these substances, including groups of compounds such as ionic liquids [ 20 , 21 , 22 , 23 ] and deep eutectic solvents [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ], as well as individual compounds, including polyethylene glycol (PEG) [ 31 , 32 , 33 ], lignin-based biopolymer (DP 2782) [ 34 ], bis(3-sulfopropyl) disulfide Na 2 [SO 3 (CH 2 ) 3 S] 2 (SPS) [ 35 ], 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulphonic acid (DPS) [ 32 ], (NaO 3 S-(CH 2 ) 3 -S-(CH 2 ) 3 -SO 3 Na) 3,3-thiobis-1-propanesulfonic acid (TBPS) [ 36 ], and the mixture of triethyl-benzyl-ammonium chloride (TEBA) with hydroxyethylated-2-butyne-l,4-diol “Ferasine” (IT-85) [ 37 ]. However, the authors’ current research stands out as it involves the use of a novel ionic liquid based on polyhexamethylenebiguanidine [ 38 ].…”