Circuit‐Level Memory Technologies and Applications based on 2D Materials

Abstract

random-access memory (DRAMs), static random-access memory (SRAMs), [1] and flash memory, [2] multiple transistors and capacitors are employed to constitute a single functional cell. These functional cells are typically integrated to form a memory array for advanced functionality, miniaturized footprints, low power consumption, and reduced latency. Traditional silicon-based complementary metal-oxidesemiconductor (CMOS) technology has been widely used to build these memory arrays. However, the performance improvement of CMOS-based memory relies on the advance of nanofabrication technology to scale down the feature size of transistors, which is approaching the physical limit. [3] To overcome this bottleneck, emerging memory technologies are brought up as promising supplements to conventional memory devices. [4] These novel types of memory include resistive random-access memory (RRAM), [5,6] ferroelectric RAM (FeRAM), [7] optoelectronic RRAM (ORRAM), [8,9] phase-change memory (PCM), [10] and spin-transfer torque magnetoresistive RAM (STT-MRAM). [11,12] Furthermore, emerging memory devices allow non-von-Neumann architectures that pave the way toward high-performance in-memory computing technology. [13,14] For example, memristive crossbar arrays composed of 1-transistor-1-resistor (1T1R) unit cells can enable in-memory computing and are the most cost-efficient thanks to their two-terminal structure. [15] Advanced 3D monolithic stacking integration also emerges as a promising approach to Memory technologies and applications implemented fully or partially using emerging 2D materials have attracted increasing interest in the research community in recent years. Their unique characteristics provide new possibilities for highly integrated circuits with superior performances and low power consumption, as well as special functionalities. Here, an overview of progress in 2D-material-based memory technologies and applications on the circuit level is presented. In the material growth and fabrication aspects, the advantages and disadvantages of various methods for producing large-scale 2D memory devices are discussed. Reports on 2D-material-based integrated memory circuits, from conventional dynamic random-access memory, static random-access memory, and flash memory arrays, to emerging memristive crossbar structures, all the way to 3D monolithic stacking architecture, are systematically reviewed. Comparisons between experimental implementations and theoretical estimations for different integration architectures are given in terms of the critical parameters in 2D memory devices. Attempts to use 2D memory arrays for in-memory computing applications, mostly on logic-in-memory and neuromorphic computing, are summarized here. Finally, challenges that impede the large-scale applications of 2D-material-based memory are reviewed, and perspectives on possible approaches toward a more reliable system-level fabrication are also given, hopefully shedding some light on future research.

Variability in Resistive Memories

“…[96][97][98] The integration of 2D materials with all electronic components could extend their functionality and help to overcome fundamental device challenges such as the gate leakage current of the transistor, temperature dissipation, and transparency. [99][100][101][102][103][104] In this application case, 2D materials help to control the RRAM C2C and D2D variability and enhance the transistor properties.…”

Two-Dimensional Layered Materials Meet Perovskite Oxides: A Combination for High-Performance Electronic Devices

“…Nonvolatile, high-speed, high-density, and low-power memory devices have long been pursued because they can substantially improve the performance of processing and storing information. , Thanks to their atomic thicknesses and diverse electronic properties, 2DLMs offer many possibilities for memory devices working on various mechanisms, including filament forming, charge trapping, and ferroelectric switching. − Dependent on the working mechanisms, a variety of corresponding device architectures have been adopted. Among them, ferroelectric field-effect transistors (FeFETs) are a promising platform to exploit the synergistic coupling between 2DLMs and ferroelectric perovskite oxides for memory devices. − , Compared with other ferroelectric materials, perovskite oxide based ferroelectric materials, such as PZT and PMN-PT, are praised for their large polarization strength, fast switching speed, and environmental stability .…”

Modulating the Performance of MoS2-Based Nanocrystal Memory via Ag Ion Implantation

“…Currently, memory manufacturers are turning to three-dimensional (3D) integration schemes to continue the historical growth rate of storage density. , 3D integration not only enhances the storage density but also overcomes some of the negative effects that are associated with physical restrictions like program noise and V T instability when the feature size goes down to 10 nm. − However, as the number of stacking layers increases, complex and tricky manufacturing processes such as etching would slow down the increasing of storage density, and stronger interlayer stress would seriously affect the reliability of storage . From a long-term perspective, it is necessary to explore simpler manufacturing methods and new reliable materials continuously for the further scaling of flash memory. , …”