Conformal Atomic Layer Deposition (ALD) of alumina on high surface-area porous copper electrodes to achieve ultra-high capacitance density on silicon interposers

This paper describes an innovative approach to achieve higher capacitance density on silicon interposers than what has been reported with trench capacitors. The approach consists of a novel silicon-compatible low-temperature sinterable metal particulate electrode and a conformal moderate K dielectric to attain the high volumetric efficiencies. The nanoparticle electrodes lead to much higher area enhancement compared to planar or trench structures resulting in ultrahigh capacitance densities. Copper nanoparticles were directly sintered on silicon substrates to form high surface area electrodes with engineered porosity. These high surface area copper electrodes were conformally-coated with moderate-permittivity dielectrics using Atomic Layer Deposition (ALD). Combination of compositional and morphological techniques, EDS and SEM respectively, were used to show alumina conformality on complex 3-D structures of copper particulate electrodes. I-V and C-V characterization was performed to confirm the feasibility of the novel high density 3-D capacitor structure. Capacitance densities of 30 μF/cm² at high voltages have been demonstrated with this approach.