Properties of Al doped Ta2O5 based MIS capacitors for DRAM applications

摘要

Al doped Ta2O5 (4; 11; 15 nm) stacks on nitrided Si obtained by rf sputtering were studied with respect to their structural, dielectric and electrical properties. Results show that the initial double-layer structure (doped Ta2O5 and interfacial SiON layer) transforms during the formation of the top Al electrode into a three-layer structure, which contains an additional layer between the Al electrode and the doped Ta2O5. It affects the dielectric properties of the stacks, deteriorating the equivalent oxide thickness (EOT). A satisfactory low level of leakage current (< 10⁻⁷ A/cm² at 1 MV/cm) is obtained in all samples. The current is mainly governed by Poole-Frenkel effect with high level of compensation, reflecting the influence of Al incorporation into the Ta2O5 films on their leakage properties.