Role of oxygen vacancies in ferroelectric or resistive switching hafnium oxide

Abstract

HfO2 shows promise for emerging ferroelectric and resistive switching (RS) memory devices owing to its excellent electrical properties and compatibility with complementary metal oxide semiconductor technology based on mature fabrication processes such as atomic layer deposition. Oxygen vacancy (Vo), which is the most frequently observed intrinsic defect in HfO2-based films, determines the physical/electrical properties and device performance. Vo influences the polymorphism and the resulting ferroelectric properties of HfO2. Moreover, the switching speed and endurance of ferroelectric memories are strongly correlated to the Vo concentration and redistribution. They also strongly influence the device-to-device and cycle-to-cycle variability of integrated circuits based on ferroelectric memories. The concentration, migration, and agglomeration of Vo form the main mechanism behind the RS behavior observed in HfO2, suggesting that the device performance and reliability in terms of the operating voltage, switching speed, on/off ratio, analog conductance modulation, endurance, and retention are sensitive to Vo. Therefore, the mechanism of Vo formation and its effects on the chemical, physical, and electrical properties in ferroelectric and RS HfO2 should be understood. This study comprehensively reviews the literature on Vo in HfO2 from the formation and influencing mechanism to material properties and device performance. This review contributes to the synergetic advances of current knowledge and technology in emerging HfO2-based semiconductor devices. Graphical Abstract

Hafnia-Based Ferroelectric Memory: Device Physics Strongly Correlated with Materials Chemistry

“…Figure c compares the various crystallographic phases observed in (Hf,Zr)­O 2 thin films . It is now accepted that the crystallographic origin of the (Hf,Zr)­O 2 thin films lies in the formation of the polar Pca 2 1 orthorhombic phase, whose crystallographic structure can be shown in the left column of Figure c.…”

“…11 Figure 1c compares the various crystallographic phases observed in (Hf,Zr)O 2 thin films. 8 It is now accepted that the crystallographic origin of the (Hf,Zr)O 2 thin films lies in the formation of the polar Pca2 1 orthorhombic phase, whose crystallographic structure can be shown in the left column of Figure 1c. It is also worth noting that the R3 or R3m rhombohedral phase can be a structural origin of ferroelectricity in epitaxial (Hf,Zr)O 2 thin films.…”

“…The properties of ferroelectric (Hf,Zr)­O 2 are strongly correlated to both intrinsic and extrinsic factors. The intrinsic factors may include thermodynamics and temperature-dependent polymorphism, while the extrinsic factors, which are the main concerns of researchers, may include the effect of doping, surface energy, strain, and oxygen vacancy. ,− …”

“…(c) Comparison table of the various crystallographic phases observed in (Hf,Zr)­O 2 thin films. Reproduced under a CC BY 4.0 license from ref .…”

Unlocking the Potential of Hafnia Ferroelectrics: Achieving High Reliability via Plasma Frequency Modulation in Very High-Frequency Plasma-Enhanced Atomic Layer Deposition

“…The limited endurance failure mechanism occurs when there is a sudden rise in leakage current, leading to hard breakdown. Endurance failure is caused by the buildup of imperfections at the border between grains, resulting in the creation of a permanent conducting path. ,, Therefore, the task of dealing with failures related to defects continues to be a challenging issue for ferroelectrics used in memory device applications.…”