Impact of inserted Ta ultrathin layer and postdeposition annealing on the forming voltage of Ir/Ti/Ta/HfO₂/TiN/Ti/SiO₂/Si resistive switching devices

Abstract

We fabricated resistive switching (RS) devices that possess the Ir/Ti/Ta/HfO2/TiN/Ti/SiO2/Si structure with different Ta and Ti layer thicknesses by a magnetron sputtering method. The lowering of forming voltage was observed when the combination of Ti and Ta layer thicknesses was Ti (45 nm)/Ta (5 nm) and the device was annealed after the deposition of the top electrode. In this sample, the migration of oxygen ions from the HfO2 layer to the Ti layer through the Ta layer upon thermal annealing was confirmed by secondary ion mass spectroscopy measurements. On the basis of the dependence of the forming voltage on the combination of the top electrode thicknesses and the presence or absence of postdeposition annealing, we discuss a method of reducing the oxide layer more effectively without changing the material combination of the metal electrode and the oxide layer.