Revival of Ferroelectric Memories Based on Emerging Fluorite‐Structured Ferroelectrics

Abstract

Over the last few decades, the research on ferroelectric memories has been limited due to their dimensional scalability and incompatibility with complementary metal‐oxide‐semiconductor (CMOS) technology. The discovery of ferroelectricity in fluorite‐structured oxides revived interest in the research on ferroelectric memories, by inducing nanoscale nonvolatility in state‐of‐the‐art gate insulators by minute doping and thermal treatment. The potential of this approach has been demonstrated by the fabrication of sub‐30 nm electronic devices. Nonetheless, to realize practical applications, various technical limitations, such as insufficient reliability including endurance, retention, and imprint, as well as large device‐to‐device‐variation, require urgent solutions. Furthermore, such limitations should be considered based on targeting devices as well as applications. Various types of ferroelectric memories including ferroelectric random‐access‐memory, ferroelectric field‐effect‐transistor, and ferroelectric tunnel junction should be considered for classical nonvolatile memories as well as emerging neuromorphic computing and processing‐in‐memory. Therefore, from the viewpoint of materials science, this review covers the recent research focusing on ferroelectric memories from the history of conventional approaches to future prospects.

Memristor-based neural networks: a bridge from device to artificial intelligence

“…The continuous intermediate state of ferroelectric polarization can be obtained by adjusting the amplitude or duration of the applied voltage pulse. 120 The reversal of the ferroelectric domain does not cause the local migration of ions or defects, thus resulting in high durability (>10 14 cycles). 121 According to the geometric structure, organic ferroelectric synapses are mainly divided into two types: two-terminal synaptic devices and three-terminal synaptic devices.…”

Emerging Fluorite-Structured Antiferroelectrics and Their Semiconductor Applications

“…Although the discovery of fluorite-structured FEs as promising materials for FE-based memory applications and energy-efficient and high-speed computing has attracted significant research interest, several issues impeding their practical implementation remain unsolved. , Because the FE phase of HfO 2 is metastable, the complex morphology of FEs in memory devices fabricated by ALD can cause device-to-device variations in different portions of the phases inside each cell. In addition, the high E c of fluorite-structured FEs results in a poor device endurance.…”

“…This trend was also observed for FeFETs with Si channels, whose poor endurance was attributed to the low-k interfacial layer of SiO x . 120,121,144 In several studies, endurance was considerably improved by substituting the low-k layer with a high-k layer. 149,150 Therefore, the AFeFET with the IGZO channel is a feasible nonvolatile structure; however, further studies on Si channels should be conducted to enhance the AFeFET performance.…”

Impact of annealing temperature on the remanent polarization and tunneling electro-resistance of ferroelectric Al-doped HfOx tunnel junction memory

“…Alongside traditional perovskite ferroelectric materials such as (Ba, Sr)TiO 3 (BST), PbZr 1-x Ti x O 3 (PZT), and SrBi 2 Ta 2 O 9 (SBT), the HfO x -based ferroelectric materials with various dopants have been extensively researched and exhibit numerous advantages such as excellent scalability, [6][7][8][9][10] ultra-low power consumption, [11][12][13][14] and good compatibility with modern very-large-scale integration (VLSI) technology. 15,16 Specific dopants include silicon (Si), aluminum (Al), gadolinium (Gd), barium (Ba), lanthanum (La), yttrium (Y), and strontium (Sr). [14][15][16][17][18][19][20][21][22][23][24] Doping hafnium oxide with various elements can strengthen its ferroelectric properties, specifically by improving the remanent polarization (P r ).…”

“…15,16 Specific dopants include silicon (Si), aluminum (Al), gadolinium (Gd), barium (Ba), lanthanum (La), yttrium (Y), and strontium (Sr). [14][15][16][17][18][19][20][21][22][23][24] Doping hafnium oxide with various elements can strengthen its ferroelectric properties, specifically by improving the remanent polarization (P r ). 19 Among these, Al has attracted significant research interest because AlO x is a commonly-used material with a high dielectric constant (k) and is widely applied in various industrial and research fields.…”