In Situ STM Imaging of Bis-3-sodiumsulfopropyl-disulfide Molecules Adsorbed on Copper Film Electrodeposited on Pt(111) Single Crystal Electrode

Abstract

The adsorption of bis-3-sodiumsulfopropyldi-sulfide (SPS) on metal electrodes in chloride-containing media has been intensively studied to unveil its accelerating effect on Cu electrodeposition. Molecular resolution scanning tunneling microscopy (STM) imaging technique was used in this study to explore the adsorption and decomposition of SPS molecules concurring with the electrodeposition of copper on an ordered Pt(111) electrode in 0.1 M HClO(4) + 1 mM Cu(ClO(4))(2) + 1 mM KCl. Depending on the potential of Pt(111), SPS molecules could react, adsorb, and decompose at chloride-capped Cu films. A submonolayer of Cu adatoms classified as the underpotential deposition (UPD) layer at 0.4 V (vs Ag/AgCl) was completely displaced by SPS molecules, possibly occurring via RSSR (SPS) + Cl-Cu-Pt → RS(-)-Pt(+) + RS(-) (MPS) + Cu(2+) + Cl(-), where MPS is 3-mercaptopropanesulfonate. By contrast, at 0.2 V, where a full monolayer of Cu was presumed to be deposited, SPS molecules were adsorbed in local (4 × 4) structures at the lower ends of step ledges. Bulk Cu deposition driven by a small overpotential (η < 50 mV) proceeded slowly to yield an atomically smooth Cu deposit at the very beginning (<5 layers). On a bilayer Cu deposit, the chloride adlayer was still adsorbed to afford SPS admolecules arranged in a unique 1D striped phase. SPS molecules could decompose into MPS upon further Cu deposition, as a (2 × 2)-MPS structure was observed with prolonged in situ STM imaging. It was possible to visualize either SPS admolecules in the upper plane or chloride adlayer sitting underneath upon switching the imaging conditions. Overall, this study established a MPS molecular film adsorbed to the chloride adlayer sitting atop the Cu deposit.

Accelerator Screening by Cyclic Voltammetry for Microvia Filling by Copper Electroplating

“…However, if an organic molecule contains an SO 3 − end group but no adsorbing group, such as HS− or −S−S−, it will have no accelerating effect on copper electrodeposition. 40 Numerous studies 21,25,33,37,38,[54][55][56][57][58][59] have confirmed that, when SPS and MPS function as accelerators for copper electrodeposition in the presence of chloride ions, the chemical adsorption of the thiol group to the copper surface is the rate-determining step, as follows:…”

“…4b, because the trans conformation of the adsorbed TBPS, SPS, and MPS can transform into a gauche conformation. 45,46,49,50,[57][58][59][61][62][63] After this process, the dehydrated Cu 2+ ions easily accept electrons from the chloride ions through an inner-sphere electron-transfer mode. 64 The gauche conformation of the adsorbed TBPS, SPS, and MPS will return to the trans conformation after Cu 2+ exchange and to trap hydrated Cu 2+ ions again, as shown in Fig.…”

Improvement on Fully Filled Through Silicon Vias by Optimized Sputtering and Electroplating Conditions

“…When developing a high quality TSV electroplating process, it is crucial to solve any problems relating to the parameters of the seed layers, solution, equipment and so on. However, only a few experimental results [15,16,17,18,19,20,21] have been reported on the effect of the parameters of seed layer sputtering and electroplating profiles on the quality of the filled copper, which has led to difficulty in optimizing the filling percentage in vias. For seed layer preparation, Song et al [15] studied the novel deposition with an atomic layer deposition and electroless seed deposition, which showed significant potential for the higher aspect ratio of TSVs.…”

“…This was assisted with pulsed power as the experimental power source and additive concentrations as the electroplating solution [19]. Analyses of the process, including cyclic voltammetry (CV) and in situ molecular resolution scanning tunneling microscopy (STM) techniques, have been utilized to illustrate the electroplating procedure [20,21]. It can be summarized that the above mentioned improvements rely mainly on the advanced equipment being complicated to operate.…”

Scanning Tunneling Microscopy of Superfilling in Formula Containing Chloride, Polyethylene Glycol and Bis-3-Sodiumsulfopropyl-Disulfide

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Within the context of our present interest of copper electrodeposition, scanning tunneling microscopy (STM) has been used to examine Cu deposition on gold electrodes with and without organic additives since the early 1990's. It is shown that surface defects of steps and vacancies are the preferred sites for Cu nucleation.…”