Stress Induced Degradation of High-k Gate Dielectric Ta2O5 Thin Films on Silicon

Abstract

This work describes the influence of constant current stress induced degradation in reactively sputtered Ta2O5 thin film in pure argon and argon plus nitrogen within plasma. Capacitors were fabricated and the interface was characterized using I-V and C-V methods. X-ray diffraction (XRD) technique revealed the presence of N2 content in Ta2O5 films. A comparison between Ta2O5 films doped with and without N2 with respect to flat band shift and leakage current density is also presented. Post deposition annealing at 650° CreducesO/Ta ratio because of the formation of suboxides. It results in high quality TaOx film with high capacitance and low leakage current. On being stressed, flat band voltage in annealed devices shifts towards negative direction as a result positive charge traps are observed in high-k thin films. Incorporation of nitrogen in Ta2O5 dielectric films retain the intrinsic effect that significantly diminish the electron leakage current through deactivating the Vo (oxygen vacancy) related gap states.