Ruthenium electrodeposition from non-aqueous electrolytes containing divalent ions

The electrodeposition of ruthenium from an ethylene glycol based electrolyte containing the metal in its divalent state is investigated for the first time. Ascorbic acid is used to reduce a fraction of the Ru(III) ions added to the non-aqueous solvent to Ru(II). Its effect is studied by means of UV–visible spectroscopy and cyclic voltammetry, demonstrating the presence of divalent ions and the stability of the electrolyte over time. Ruthenium coatings are deposited on gold-sputtered silicon wafers under galvanostatic conditions at various current densities and deposition times. The characterizations carried out evidence the significant purity of the ruthenium film, while the morphological analysis reveals its compact and crack-free morphology. Indeed, thicknesses up to 2.35 µm are successfully plated with no sign of delamination or cracking. The good electrical properties observed for the deposited layers validate the possible applicability of the Ru(II) containing non-aqueous electrolyte here described to the manufacturing of integrated circuits interconnects or contacts for electrical applications.