Ferroelectric HfO₂-based synaptic devices: recent trends and prospects

Abstract

Neuro-inspired deep learning algorithms have shown promising futures in artificial intelligence. Despite the remarkable progress in software-based neural networks, the traditional von-Neumann hardware architecture has suffered from limited energy efficiency while facing unprecedented large amounts of data. To meet the performance requirements of neuro-inspired computing, large-scale vector-matrix multiplication is preferred to be performed in situ, namely compute-in-memory. Non-volatile memory devices with different materials have been proposed for weight storage as synaptic devices. Among them, HfO 2 -based ferroelectric devices have attracted great attention because of their low energy consumption, good complementarymetal-oxide-semiconductor (CMOS) compatibility and multi-bit per cell potential. In this review, recent trends and prospects of the ferroelectric synaptic devices are surveyed. First, we present the three-terminal synaptic devices based on the ferroelectric field effect transistor (FeFET), and discuss the switching physics of the intermediate states, the back-end-of-line integration and the 3D NAND architecture design. Then, we introduce a hybrid precision synapse concept that leverages the volatile charges on the gate capacitor of the FeFET and the non-volatile polarization on the gate dielectric of the FeFET. Lastly, we review two-terminal synaptic devices using the ferroelectric tunnel junction (FTJ) and ferroelectric capacitor (FeCAP). The design margins of the crossbar array with FTJ and FeCAP analyzed.

Ferroelectric Hf0.5Zr0.5O2 films on SrTiO3(111)

“…The discovery 1 of ferroelectricity in a metastable orthorhombic phase (Pca2 1 space group) of Si-doped HfO 2 has generated huge interest. [2][3][4][5][6][7] The ferroelectric phase has also been stabilized in HfO 2 doped with other atoms. 7,8 The ferroelectric properties of HfO 2 have been investigated mainly in polycrystalline films, although there is increasing interest in epitaxial films after the demonstration of epitaxial stabilization on yttria-stabilized zirconia 9 and perovskite [10][11][12] single crystalline substrates.…”

STeP-CiM: Strain-Enabled Ternary Precision Computation-In-Memory Based on Non-Volatile 2D Piezoelectric Transistors

“…However, it suffers from issues such as destructive read and low distinguishability between the memory states. Ferroelectric FETs (FEFETs), in which the ferroelectric material is integrated within the gate stack of a transistor (Yu et al, 2021), offer appealing attributes that mitigate the concerns of FERAMs. For instance, FEFETs feature separation of read-write paths, non-destructive read, and high distinguishability while retaining the benefits of electric field-driven write (Yu et al, 2021) and offering other advantages such as multilevel storage (Ni et al, 2018;Dutta et al, 2020;Kazemi et al, 2020;Liao et al, 2021).…”

“…Ferroelectric FETs (FEFETs), in which the ferroelectric material is integrated within the gate stack of a transistor (Yu et al, 2021), offer appealing attributes that mitigate the concerns of FERAMs. For instance, FEFETs feature separation of read-write paths, non-destructive read, and high distinguishability while retaining the benefits of electric field-driven write (Yu et al, 2021) and offering other advantages such as multilevel storage (Ni et al, 2018;Dutta et al, 2020;Kazemi et al, 2020;Liao et al, 2021). However, they are known to suffer from variability, endurance, and retention concerns due to traps at the ferroelectric-dielectric interface and depolarization fields in the ferroelectric.…”

HfO2-based resistive switching memory devices for neuromorphic computing

“…HfO 2 based stacks have been proposed and optimized toward nonvolatile RRAM since more than 15 years [4,6,13,19]. In addition, HfO 2 possesses a set of key properties, including (i) high dielectric constant for scalable CMOS technology, both for logic and charge trap memory devices [20,21], (ii) controllable ferroelectricity/antiferroelectricity behavior for high density memory and for synaptic devices [22,23], and (iii) high compatibility with the CMOS process. HfO 2 thus appears as a dielectric material of choice for microelectronic systems encompassing logic, memory and neuromorphic functions on the same chip.…”