High capacitance density of 185 nF/mm2 achieved in three-dimensional MIM structures using TiO2 as a dielectric

In this paper, three-dimensional (3D) metal-insulator-metal (MIM) structures were obtained by atomic layer deposition of an aluminum doped TiO2 layer on a dense array of truncated conical holes etched in a silicon substrate. Different features of conical holes were fabricated in order to increase the developed area of the MIM structure. A capacitance density of nearly 185 nF/mm2 was obtained on an array of 19.2 μm deep holes with 5 and 10 μm bottom and top conical hole diameters, respectively. Interestingly, the increase in capacitance density scales with the developed area and no degradation of the electrical properties of the MIM structure has been observed. Indeed, the leakage current across the 3D MIM structures remains as small as in planar (2D) MIM structures.