Ionizing radiation effects on electrical and reliability characteristics of sputtered Ta2O5/Si interface

Abstract

This paper describes the effect of ionizing radiation on the interface properties of Al/Ta2O5/Si metal oxide semiconductor (MOS) capacitors using capacitance–voltage (C–V) and current–voltage (I–V) characteristics. The devices were irradiated with X-rays at different doses ranging from 100 rad to 1 Mrad. The leakage behavior, which is an important parameter for memory applications of Al/Ta2O5/Si MOS capacitors, along with interface properties such as effective oxide charges and interface trap density with and without irradiation has been investigated. Lower accumulation capacitance and shift in flat band voltage toward negative value were observed in annealed devices after exposure to radiation. The increase in interfacial oxide layer thickness after irradiation was confirmed by Rutherford Back Scattering measurement. The effect of post-deposition annealing on the electrical behavior of Ta2O5 MOS capacitors was also investigated. Improved electrical and interface properties were obtained for samples deposited in N2 ambient. The density of interface trap states (Dit) at Ta2O5/Si interface sputtered in pure argon ambient was higher compared to samples reactively sputtered in nitrogen-containing plasma. Our results show that reactive sputtering in nitrogen-containing plasma is a promising approach to improve the radiation hardness of Ta2O5/Si MOS devices.