Ferroelectric HfO₂-based materials for next-generation ferroelectric memories

Abstract

Ferroelectric random access memory (FeRAM) based on conventional ferroelectric perovskites, such as Pb(Zr,Ti)O 3 and SrBi 2 Ta 2 O 9 , has encountered bottlenecks on memory density and cost, because those conventional perovskites suffer from various issues mainly including poor complementary metal-oxide-semiconductor (CMOS)-compatibility and limited scalability. Nextgeneration cost-efficient, high-density FeRAM shall therefore rely on a material revolution. Since the discovery of ferroelectricity in Si:HfO 2 thin films in 2011, HfO 2 -based materials have aroused widespread interest in the field of FeRAM, because they are CMOScompatible and can exhibit robust ferroelectricity even when the film thickness is scaled down to below 10 nm. A review on this new class of ferroelectric materials is therefore of great interest. In this paper, the most appealing topics about ferroelectric HfO 2 -based materials including origins of ferroelectricity, advantageous material properties, and current and potential applications in FeRAM, are briefly reviewed.

Van der Waals engineering of ferroelectric heterostructures for long-retention memory

“…However, the severe depolarization effects and carrier charge trapping drastically limit the memory retention time, and prevent the commercialization of nonvolatile memory potential of FeFET using the commercially available ferroelectrics 9 – 11 . Furthermore, attempts to synthesize ferroelectrics on semiconductors are impeded by ferroelectric-semiconductor interdiffusion and lattice mismatch 12 , 13 .…”

Epitaxial Integration on Si(001) of Ferroelectric Hf0.5Zr0.5O2 Capacitors with High Retention and Endurance

“…1 The ferroelectric phase is usually stabilized in polycrystalline films where nanometric orthorhombic grains coexist with other dielectric phases. [2][3][4] The inherent inhomogeneity of polycrystalline films challenges the understanding of the intrinsic mechanisms of ferroelectricity in HfO2 and its optimization. Moreover, oxygen vacancies form close to the interfaces with the commonly used TiN electrodes.…”

Electric-field-controlled interface dipole modulation for Si-based memory devices

“…Therefore, the effect of ferroelectric HfO 2 can also be eliminated, even for a multi-stack HfO 2 /SiO 2 IDM structure. In general, the formation of a ferroelectric HfO 2 film requires annealing at a temperature above 450 °C and the thinnest HfO 2 film employed in their experiments is 5 nm 7 – 12 , 17 , 36 , 37 . The annealing temperature of the six-stacked IDM structure shown in Fig.…”