Adsorption and Desorption of Bis-(3-sulfopropyl) Disulfide during Cu Electrodeposition and Stripping at Au Electrodes

Abstract

The adsorption and desorption of bis-(3-sulfopropyl) disulfide (SPS) on Cu and Au electrodes and its electrochemical effect on Cu deposition and dissolution were examined using cyclic voltammetry stripping (CVS), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). SPS dissociates into 3-mercapto-1-propanesulfonate when it is contacted with Au and Cu electrodes, producing Cu(I)- and Au(I)-thiolate species. These thiolates couple with chloride ions and promote not only the reduction of Cu(2+) in Cu deposition but also the oxidation of Cu(0) to Cu(+) in Cu stripping. During Cu electrodeposition on the SPS-modified Au electrode, thiolates transfer from Au onto the Cu underpotential deposition (UPD) layer. The Cu UPD layer stabilizes a large part of the transferred thiolates which subsequently is buried by the Cu overpotential deposition (OPD) layer. The buried thiolates reappear on the Au electrode after the copper deposit is electrochemically stripped off. A much smaller part of thiolates transfers to the top of the Cu OPD layer. In contrast, when SPS preadsorbs on a Cu-coated Au electrode, almost all of the adsorbed SPS leaves the Cu surface during Cu electrochemical stripping and does not return to the uncovered Au surface. A reaction mechanism is proposed to explain these results.

Accelerator Screening by Cyclic Voltammetry for Microvia Filling by Copper Electroplating

“…These Cu-thiolates can desorb from the copper surface under a bias of cathodic potential, 52,53 which results in these thiolates being transferrable. 39 Therefore, the adsorbed TBPS, SPS, and MPS transfer onto the as-deposited copper layer, as illustrated in Fig. 4d.…”

“…This electrolyte composition can be used to characterize the accelerating effect of MPS and SPS on copper electrodeposition. 39,51 If the organosulfides can accelerate copper electrodeposition, and if it is transferable from the surface of the modified Au electrode onto the perimeter of the asdeposited copper during copper electrodeposition, then α peaks will be formed, as shown in Fig. 2.…”

“…25,38,39,[45][46][47][48][49][50][51] If an organic additive can interact with chloride ions to accelerate copper nucleation and deposition, then the additive can adsorb onto a Cu or Au surface and can float on the copper deposit during electroplating. 31,38,39 The floatability of the organic additive determines its accelerating ability. 31,38,39 Cyclic voltammetry (CV) can be used to characterize the accelerating ability and the floatability of the accelerator using an Au electrode.…”

“…31,38,39 The floatability of the organic additive determines its accelerating ability. 31,38,39 Cyclic voltammetry (CV) can be used to characterize the accelerating ability and the floatability of the accelerator using an Au electrode. 39,51 CV is performed in an electrolyte solution that contains copper ions, H 2 SO 4 , PEG, and chloride ions.…”

Nanofabrication techniques of highly organized monolayers sandwiched between two electrodes for molecular electronics

“…Overpotential deposition (OPD) of metals on monolayers results in metallic films that are above the organic film but are also frequently accompanied by metallic filaments that are in electrical contact with the bottom electrode rendering the device unusable [255]. Alteration of the monolayer integrity upon underpotential deposition (UPD) has also been described [253,256]. Recently, a successful electrochemical deposition of palladium onto a pyridine-terminated monolayer has been reported [257].…”