Layered Cu-based electrode for high-dielectric constant oxide thin film-based devices

Abstract

Ti–Al/Cu/Ta multilayered electrodes were fabricated on ${\mathrm{SiO}}_2/\mathrm{Si}$ substrates by ion beam sputtering deposition, to overcome the problems of Cu diffusion and oxidation encountered during the high dielectric constant (κ) materials integration. The Cu and Ta layers remained intact through the annealing in oxygen environment up to $\text{600\hspace{0.05em}°}\mathrm{C}.$ The thin oxide layer, formed on the Ti–Al surface, effectively prevented the oxygen penetration toward underneath layers. Complex oxide $({\mathrm{Ba}}_x{\mathrm{Sr}}_{\text{1−x}}){\mathrm{TiO}}_3$ (BST) thin films were grown on the layered Ti–Al/Cu/Ta electrodes using rf magnetron sputtering. The deposited BST films exhibited relatively high permittivity (150), low dielectric loss (0.007) at zero bias, and low leakage current ${\text{<2×10}}^{\text{−8}}\hspace{0.17em}{\mathrm{A/cm}}^2$ at 100 kV/cm.