Resistive random-access memory
ReRAM bears some similarities to conductive-bridging RAM (CBRAM) and phase-change memory (PCM) in that they change dielectric material properties.
RRAM is the registered trademark name of Sharp Corporation, a Japanese electronic components manufacturer, in some countries, including members of the European Union.
[2] An energy-efficient chip called NeuRRAM fixes an old design flaw to run large-scale AI algorithms on smaller devices, reaching the same accuracy as digital computers, at least for applications needing only a few million bits of neural state.
[7] Panasonic launched a ReRAM evaluation kit in May 2012, based on a tantalum oxide 1T1R (1 transistor – 1 resistor) memory cell architecture.
[10] Different forms of ReRAM have been disclosed, based on different dielectric materials, spanning from perovskites to transition metal oxides to chalcogenides.
[18]: 1180 In May 1997, a research team from the University of Florida and Honeywell reported a manufacturing method for "magneto-resistive random access memory" by utilizing electron cyclotron resonance plasma etching.
Filamentary and homogenous conduction path switching effects can be distinguished by measuring the area dependence of the low-resistance state.
On the other hand, a cross-point architecture is more compact and may enable vertically stacking memory layers, ideal suited for mass-storage devices.
Such isolation capabilities are inferior to the use of transistors if the on/off ratio for the selector is not sufficient, limiting the ability to operate very large arrays in this architecture.
These can be grouped into the following categories:[34] ABO3-type inorganic perovskite materials such as BaTiO3, SrRuO3, SrZrO3, and SrTiO3 have attracted extensive research interest as the storage media in memristors due to their remarkable resistance switching effects and various functionalities such as ferroelectric, dielectric, and semiconducting physical characteristics.
[44] However, the fragile nature and high cost of the fabrication process limit the wide applications of these ABO3-type inorganic perovskite materials for memristors.
Recently, ABX3-type lead trihalide perovskites have received extensive research interest for using in optoelectronic devices such as photovoltaics, photodetectors, and light-emitting diodes (LED).
[45] In these structures, A is a monovalent organic or inorganic (MA:CH3NH3+, FA: CH(NH2)2+, Cs+, Rb+), B is a divalent metal cation (Pb2+, Sn2+), and X is a halide anion (Cl, Br, I).
[16] Nevertheless, owing to the inclusion of organic cations, it was commonly found that the intrinsic thermal instability of methylammonium (MA) and formamidinium (FA) lead trihalide perovskites was really a bottleneck for the development of hybrid perovskite-based electronic devices.
Interestingly, there are some reports of Cesium/Cesium hybridization solar cells that give us many new clues for the improved stability of all-inorganic perovskite-based electronic devices.
[48] Therefore, it has been implied that all-inorganic perovskites could be excellent candidates for the fabrication of stable and highly efficient resistive switching memory devices using a low-cost process.
Considering the CsPbX3 perovskites are usually prepared by solution method, point defects such as vacancies, interstitials, and antisites are possible in the crystals.
A 32 Gb 24 nm ReRAM was published by SanDisk in 2013 without many details other than a non-transistor access device, and metal oxide RRAM composition.
[53] At IEDM 2008, the first high-performance ReRAM technology was demonstrated by ITRI using HfO2 with a Ti buffer layer, showing switching times less than 10 ns and currents less than 30μA.
[54] IMEC presented updates of their ReRAM program at the 2012 Symposia on VLSI Technology and Circuits, including a solution with a 500 nA operating current.
[60] A key requirement was the need for a high work function metal such as Pt or Ir to interface with the TaOx layer.
[66] On 30 April 2008, HP announced that they had discovered the memristor, originally envisioned as a missing 4th fundamental circuit element by Chua in 1971.
[78] In September 2021, Weebit, together with Leti, produced, tested and characterized a 1 Mb ReRAM array, using a 28 nm FDSOI process on 300mm wafers.
Memory operating mechanism is proposed based on charge trapping in quantum dots with AlOx acting as barrier.
A vertical 1D1R (one diode, one resistive switching device) integration can be used for crossbar memory structure to reduce the unit cell size to 4F² (F is the feature dimension).
[94] A significant hurdle to realizing the potential of ReRAM is the sneak path problem that occurs in larger passive arrays.
A drawback to the initial CRS solution is the 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.
[101] Modeling of 2D and 3D caches designed with ReRAM and other non-volatile random access memories such as MRAM and PCM can be done using DESTINY[102] tool.
