Controlling Filament Stability in Scaled Oxides (3 nm) for High Endurance (>10 6 ) Low Voltage ITO/HfO 2 RRAMs for Future 3D Integration

Non-volatile resistive-random-access-memories (RRAMs), which are highly scalable, cost-efficient and fast, are needed to meet the future computational needs beyond the traditional von-Neumann architecture. Oxygen vacancy RRAMs in particular have been demonstrated to operate at nanosecond programming ranges with low voltages as well as being integrated in dense cross-point arrays [1] . ITO/HfO 2 based RRAMs have emerged as a promising material stack due to its ultra-low switching voltages, self-compliance properties and the transparency of ITO that extends the material stack’s applications into display/wearable electronics [2] . As the different RRAM technologies are reaching maturity, scaling down the oxide thicknesses is now becoming vital for compatibility with dense 3D integration as projected by the IRDS 2020 [3] . We report that, when operated at relevant current levels (sub 100 µA), the filament integrity of ITO/HfO 2 RRAM with a thin high-k oxide (3 nm) can be controlled depending on the deposition conditions, where a thermal ALD (TALD) process results in a stable filament formation as compared to a plasma enhanced ALD (PEALD) process used for depositing HfO 2 . Our results further indicate that the RRAM RESET is more gradual for the TALD (oxygen deficient) HfO 2 as compared to the abrupt switching behavior for the PEALD (oxygen rich) HfO 2 . The observed gradual filament reduction can be beneficial for multibit operation. Moreover, by using a single vertical nanowire (VNW)-MOSFET connected externally in series for DC measurements ,as shown in Fig. 1 , we also make sure the current levels remain compatible for direct state-of-the-art selector integration [4] [5] .