Resistive switching memories based on metal oxides: mechanisms, reliability and scaling

Abstract

With the explosive growth of digital data in the era of the Internet of Things (IoT), fast and scalable memory technologies are being researched for data storage and data-driven computation. Among the emerging memories, resistive switching memory (RRAM) raises strong interest due to its high speed, high density as a result of its simple two-terminal structure, and low cost of fabrication. The scaling projection of RRAM, however, requires a detailed understanding of switching mechanisms and there are potential reliability concerns regarding small device sizes. This work provides an overview of the current understanding of bipolarswitching RRAM operation, reliability and scaling. After reviewing the phenomenological and microscopic descriptions of the switching processes, the stability of the low-and high-resistance states will be discussed in terms of conductance fluctuations and evolution in 1D filaments containing only a few atoms. The scaling potential of RRAM will finally be addressed by reviewing the recent breakthroughs in multilevel operation and 3D architecture, making RRAM a strong competitor among future high-density memory solutions.

The role of nitrogen doping in ALD Ta2O5 and its influence on multilevel cell switching in RRAM

“…It has been shown in the literature 3,4 and is shown in this work that atomic doping can improve both requirements. Evolution of a conductive filament and its rupture and restoration have been studied by various analytical and numerical models [10][11][12][13][14] We have previously reported the properties of Ovac in the λ phase of Ta2O5 crystal 15 and in the amorphous Ta2O5 network 16 through sX density functional simulations. It is found that the 2-fold Ovac in both networks has a small formation energy, low diffusion barrier, and deep defect states below the conduction band, believed to be strongly related to the resistive switching behavior in the RRAM devices.…”

Total-Ionizing-Dose Effects on Threshold Switching in $1{T}$ -TaS2 Charge Density Wave Devices

“…In TaO x devices, just 10 krad(SiO 2 ) irradiation flipped the OFF (high resistance) state to ON (low resistance) state with a 100-fold decrease in resistance in [21]. On the other hand, HfO 2 -based resistive memory elements have carrier densities of ∼10 20 cm −3 in their conductive state [23], and have been demonstrated to be quite tolerant to TID exposure above 1 Mrad(SiO 2 ) [24], consistent with this interpretation.…”

Emulator Circuits and Resistive Switching Parameters of Memristor

“…The filament-type mechanism is associated with the formation and rupture of conductive filaments in the active layer. Both types of mechanisms can be observed in the memristor devices as shown in Figure 9 and depend on the material and fabrication methods [18].…”

“…Unipolar operation is more striking than bipolar operation in memristor switching devices, since it needs simple circuits. But then, bipolar operation has generally high uniformity and more endurance compared to unipolar operation [18].…”

“…It is well known that reversible switching between a low-resistance state (LRS) or ON (SET) and a high-resistance state (HRS) or OFF (RESET) can be achieved by applying a certain voltage [18]. Operation voltage is also an important value for CMOS or other device integrations for memristor devices.…”