Molecule of the Month
May 2011
Competitive Anion Interactions at Copper/Electrolyte Interfaces

The time-dependent, competitive interaction between chloride anions and SPS (Bis-(3-sulfopropyl)-disulfid) for adsorption sites on copper/electrolyte interfaces is of central importance for the so-called Copper Damascene Process. Copper electrodeposition is used in today's microprocessor fabrication for the metallization of interconnects on Si-chips. The diameter of those copper interconnects currently approaches the sub-50nm regime (22nm and 16nm technology).
In the course of the copper electro-deposition SPS dissociates on the metallic copper surface at defect sites within the pre-existing chloride matrix leaving co-adsorbed MPS (3-mercapto-propyl-sulfonic acid) behind. While the chloride-terminated copper surface allows the adsorption of PEG (polyethylene glycols) suppressor polymers the co-adsorbed MPS disturbs this specific PEG/Cl interaction thereby keeping the copper electrode active for the copper deposition.

This work was carried out in the group of PD Dr. Peter Broekmann.


  • P. Broekmann, A. Fluegel, C. Emnet, M. Arnold, C. Roeger-Goepfert, A. Wagner, N.T.M. Hai, D. Mayer;
    "Classification of suppressor additives based on synergistic and antagonistic ensemble effects"
    Electrochimica Acta, 56, 4724-4734, (2011); doi:10.1016/j.electacta.2011.03.015.