Modeling of the Coadsorption of Chloride and Hydrogen Ions on Copper Electrode Surface

Abstract

For manufacturing copper interconnects by the damscence technique, electrochemical deposition of copper on patterned sustrates requires several additives to achieve compact filling of trenches and vias, where chloride ions play a crucial role. In the highly acidic electrolyte, adsorption of chloride ions on copper is expected to compete with the adsorption of hydrogen, depending on the copper electrode potential. We propose a general phenomenological model of the coadsorption of two ion species which is supported by DFT calculations and show how the adsorption of one species can be described by the common Langmuir model with rescaled parameters depending on the concentration of the second species. Regarding the Cl − -H + -system, corresponding model parameters are estimated by fitting radio tracer measurements of the chloride adsorption on copper reported in the literature. The data suggest that in a highly acidic solution (pH ≈ 0) the saturation surface density of chloride depends strongly on the electrode potential. With variation of the potential E S H E from −0.4 to +0.2 V, the saturation density changes by a factor of four. Within our model, such a potential dependence of the saturation density is explained by the presence of adsorbed hydrogen.

Properties and microstructure regulation of electrodeposited ultra-thin copper foil in a simple additive system

“…Pinhole generation is a complex phenomenon. Chloride ions in VMS tend to adsorb on the microscopically convex part of the substrate [30], while hydrogen ions tend to adsorb on the microscopically concave part of the substrate due to competitive adsorption behavior with chloride ions on the copper surface [35]. The presence of chloride ions without HEC accelerated the deposition of copper, leading to a rapid depletion of copper ions in the microregion.…”