Performance Improvement of an Al/TiO2/Al Electronic Bipolar Resistive Switching Memory Cell via Inserting an Ultrathin ZrO2 Layer

The Al/TiO2/Al resistance random access memory (ReRAM) showed an area-type electronic bipolar resistive switching (e-BRS) mechanism, which was mediated by the trapping and detrapping of the carriers at the trap centers. The area-type e-BRS device had area-scalable characteristics and excellent uniformity, which are beneficial for large-scale integrated applications. However, the unsatisfactory endurance and retention performance needed to be improved. In this work, a 1–2 nm thick ZrO2 thin layer was deposited by the thermal atomic layer deposition on the 25 nm thick sputter-deposited TiO2 layer to form an Al/ZrO2/TiO2/Al memory cell. The thin ZrO2 layer effectively prevented the active Al top electrode from absorbing oxygen from the TiO2 resistive switching (RS) layer without significantly affecting the asymmetric energy barrier structure of the device. The suppression of oxygen loss from the TiO2 RS layer retained the desired trap density of the RS layer even after the extended switching cycle operation. This suppression effect significantly improved the RS performances, such as endurance, uniformity, and retention. The switching endurance was enhanced by over 2 orders of magnitudes (from <103 to >105). The ZrO2 layer also increased the overall resistance values of the memory cell, making it more suitable than the Al/TiO2/Al structure for high-density applications.