Rapid thermal annealing on the atomic layer-deposited zirconia thin film to enhance resistive switching characteristics

The resistive switching random access memory (RRAM) device has received a great interest for the next-generation non-volatile memory application, and resistive switching (RS) characteristics are mainly affected by conductive oxygen vacancies ([V_o^··]) within switching material. Various effective approaches with materials, doping, and thermal treatments have been attempted to achieve the stable RS behaviors. Particularly, thermal annealing is considered as an efficient knob to control [V_o^··] compared to other approaches. However, research on thermal treatment still lacks results and further research efforts are still needed to improve the RS characteristics of the devices. In this work we investigated the RS characteristics of Ti/ZrO_x/Pt-structured RRAM device in comparison without and with postrapid thermal annealing (RTA) temperature range under oxygen ambient. The as-fabricated device with atomic layer-deposited ZrO_x switching layer exhibited conducting characteristics, which is related to a relatively high amount of [V_o^··] within switching medium. It indicates that moderate amount of [V_o^··] apparently determines the appropriate RS behaviors. With this regard, we modulated the [V_o^··] in ZrO_x thin films by employing RTA in the ranges of 500 °C to 800 °C at the oxygen ambient for 60 s. Unlike device without RTA, we observed the stable RS characteristics from device with RTA and device annealed at 700 °C exhibits the excellent bipolar RS characteristics such as higher R_on/R_off, smaller cycle-to-cycle switching variation, better endurance, and longer retention among RTA conditions, indicating moderate amount of [V_o^··] formed within ZrO_x thin film layer. Moreover, increasing ALD ZrO_x thickness shows the further improvement in the RS characteristics and RTA on the thicker ZrO_x device still improves the RS behaviors. This research indicates that modulating [V_o^··] by fast thermal annealing on the ALD zirconia material can provide the proper RS characteristics of the non-volatile memory applications.