Ultrahigh Capacitance Density for Multiple ALD-Grown MIM Capacitor Stacks in 3-D Silicon

ldquoTrenchrdquo capacitors containing multiple metal-insulator-metal (MIM) layer stacks are realized by atomic-layer deposition (ALD), yielding an ultrahigh capacitance density of 440 at a breakdown voltage V_DB > 6 V. This capacitance density on silicon is at least 10times higher than the values reported by other research groups. On a silicon substrate containing high-aspect-ratio macropore arrays, alternating MIM layer stacks comprising high-k Al₂O₃dielectrics and TiN electrodes are deposited using optimized ALD processing such that the conductivity of the TiN layers is not attacked. Ozone annealing subsequent to each Al₂O₃ deposition step yields significant improvement of the dielectric isolation and breakdown properties.