High-density capacitors with conformal high-k dielectrics on etched-metal foils

This paper describes the fabrication and characterization of high-density capacitors using etched-metal foils as high-surface area electrodes. High permittivity films were conformally-formed over the metal foils using an anodization reaction. The approach was demonstrated with two material systems, viz., etched aluminum foils and porous titanium foils. Both the metal anodizations were carried out with aqueous solution of citric acid as electrolytes. The electrical properties of the etched-foil capacitor were measured using a sulfuric acid solution as the top contact. The high surface area electrodes yielded very high capacitance densities of 35-40 μF/cm².