Effect of thermal annealing on resistance switching characteristics of Pt/ZrO2/TiN stacks

In this study, the effect of thermal annealing on both the physical properties and the resistive switching properties of ZrO2 films deposited by atomic layer deposition (ALD) method were investigated for its potential application to non-volatile memory devices. The ZrO2 films in the Pt/ZrO2/TiN structure exhibited unipolar and bipolar resistance switching behaviors depending on the nature of the bias applied to Pt top electrodes for the electro-forming process. For unipolar switching, the resistance of the high resistance state (HRS) was reduced with increasing annealing temperature, accompanied with the increase of metallic Zr in the annealed ZrO2 films. In contrast, the HRS resistance in the bipolar switching was increased while the low resistance state (LRS) resistance was decreased with increasing annealing temperature, producing a greater change in resistance. SIMS and EDX showed that the thickness of interfacial TiOxNy layer between the ZrO2 and the TiN bottom electrode was enlarged with annealing. The enlarged TiOxNy layer was expected to produce the reduction of LRS resistance with the increase of HRS resistance in the bipolar resistance switching.