Mechanisms of Solid Electrolyte Deposition of Copper Using Cation Exchange Membrane

Abstract

Efficient electrodeposition can be accomplished using solid electrolyte deposition (SED) with a cation exchange membrane as an electrolyte because the electric field imposed on the electrolyte membrane can control the mass transfer of metallic ions. Salient benefits of SED include the following: (1) Pattern plating can be conducted easily. The handling of an electrochemical cell is extremely simple because of its solid electrolyte usage. (2) Post-treatment of the electrode is unnecessary because the solid electrolyte contacting the electrode surface can be removed after electrodeposition. (3) High-rated plating can be expected because the driving force of the mass transfer of the reactants is expected to be migration. To verify those benefits, electrochemical measurements were conducted. Current-potential curves show the current density in the SED to be higher than that obtained using copper electrodeposition in the same concentration of CuSO 4 solution as that for the SED. Moreover, the patterning was easy. Post-treatment was unnecessary because copper was deposited only on the substrate contacted with the solid electrolyte. We propose a mass transfer mechanism that occurs during SED processing using a solid electrolyte. The relation between overvoltage and the current density during SED is explained clearly by the mechanism.