A study on the capacitance–voltage characteristics of metal-Ta2O5-silicon capacitors for very large scale integration metal-oxide-semiconductor gate oxide applications

In this work, the capacitance–voltage characteristics of Au/Ta2O5/Si capacitors are studied. The Ta2O5 films are deposited by plasma-enhanced chemical vapor deposition system. Constant voltage stress is applied to the Ta2O5 capacitors. The flatband voltage VFB is measured before and after the constant voltage stress. The flatband voltage shift due to the stress is explained by the trapping of electrons and holes. An interface trapped charge density (Dit) about 2×1011 eV−1 cm−2 in the midgap of silicon is extracted by using the conductance method. The discharging transient current after a constant voltage stress is measured and correlated with the electron and hole trapping. The trapped electron and hole densities in Ta2O5 are calculated by using the tunneling front model. The VFB shift and the discharging transient currents are explained based on the energy band diagram of the metal/Ta2O5/silicon system.