Future Applications
ReRAM has the potential to become the front runner among other non-volatile memories. Compared to PRAM, ReRAM operates at a faster timescale (switching time can be less than 10 ns), while compared to MRAM, it has a simpler, smaller cell structure (less than 8F² MIM stack). There is a type of vertical 1D1R (one diode, one resistive switching device) integration used for crossbar memory structure to reduce the unit cell size to 4F² (F is the feature dimension). Compared to flash memory and racetrack memory, a lower voltage is sufficient and hence it can be used in low power applications.
ITRI has recently shown that ReRAM is scalable below 30 nm. The motion of oxygen atoms is a key phenomenon for oxide-based ReRAM; one study has indicated that oxygen motion may take place in regions as small as 2 nm. It is believed that if a filament is responsible, it would not exhibit direct scaling with cell size. Instead, the current compliance limit (set by an outside resistor, for example) could define the current-carrying capacity of the filament.
A significant hurdle to realizing the potential of ReRAM is the sneak path problem which occurs in larger passive arrays. In 2010, complementary resistive switching (CRS) was introduced as a possible solution to the interference from sneak-path currents. In the CRS approach, the information storing states are pairs of high and low resistance states (HRS/LRS and LRS/HRS) so that the overall resistance is always high, allowing for larger passive crossbar arrays.
A drawback to the initial CRS solution is the high requirement for switching endurance caused by conventional destructive readout based on current measurements. A new approach for a nondestructive readout based on capacity measurement potentially lowers the requirements for both material endurance and power consumption. Bi-layer structure is used to produce the nonlinearity in LRS to avoid the sneak path problem. Single layer device exhibiting a strong nonlinear conduction in LRS has been recently reported. Another bi-layer structure is introduced for bipolar ReRAM to improve the HRS and stability of the memory endurance performance.
Read more about this topic: Resistive Random-access Memory
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