Constructing a correlation between ferroelectricity and grain sizes in Hf0.5Zr0.5O2 ferroelectric thin films

Chen, Haiyan; Luo, Hang; Yuan, Xiaoyan; Zhang, Ye

doi:10.1039/d1ce01626a

Cited by 25 publications

(18 citation statements)

References 46 publications

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“…It has been reported that the ferroelectricity of HZO films is enhanced with smaller grain size. 15,52 Significantly, for conventional perovskite ferroelectric materials, massive grain size exhibits robust polarization. 56,57 This indicates that the mechanism of grain size effect in regulating the ferroelectricity of HZO films is completely different from that of conventional ferroelectric materials.…”

Section: Resultsmentioning

confidence: 99%

“…39 Apart from the use of different electrodes, the grain size can also be modulated by other methods. For example, Chen et al 15 experimentally studied the effects of the annealing process (annealing temperature and annealing time) on the grain size, furthering accurate modulation of HZO thin films ferroelectric properties from 5 to 25 μC/cm 2 . Moreover, Chen et al compared the effect of high-temperature ALD (300 °C) and low-temperature ALD (200 °C) on grain size, demonstrating that the low-temperature deposition process brings profitable gains in polarization value, breakdown voltage, and frequency response.…”

Section: Resultsmentioning

confidence: 99%

“…It is generally believed that the thickness of the HZO film is proportional to the grain size. 15,46 With the scaling down of semiconductor technology nodes, such as nanoscale size and ultrathin HZO films, the effective number, inhomogeneity, and switching randomness of ferroelectric domains become worse, causing thorny control problems and collapse of memory window (MW) for nanoscale level devices. 63 At this point, it is increasingly challenging to regulate ferroelectric properties from the strain perspective.…”

Section: Resultsmentioning

confidence: 99%

“…), 14 and also the annealing process. 15 Among all the above-mentioned manipulation strategies, the top capping electrodes play a critical role in the ferroelectricity of hafnium-based devices. For example, Franklin et al 16 elemental metal electrodes on the ferroelectric properties of HZO thin films and found that different electrode materials combined with annealing temperature or film thickness could flexibly regulate the ferroelectric properties.…”

Section: Introductionmentioning

confidence: 99%

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Understanding the Effect of Top Electrode on Ferroelectricity in Atomic Layer Deposited Hf_0.5Zr_0.5O₂ Thin Films

Wang

Wen

et al. 2023

ACS Appl. Mater. Interfaces

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It is commonly believed that the impact of the top electrodes on the ferroelectricity of hafnium-based thin films is due to strain engineering. However, several anomalies have occurred that put existing theories in doubt. This work carries out a detailed study of this issue using both theoretical and experimental approaches. The 10 nm Hf0.5Zr0.5O2 (HZO) films are prepared by atomic layer deposition, and three different top capping electrodes (W/MO/ITO) are deposited by physical vapor deposition. The electrical testing finds that the strain does not completely control the ferroelectricity of the devices. The results of further piezoelectric force microscopy characterization exclude the potential interference of the top capping electrodes and interface for electrical testing. In addition, through atomic force microscopy characterization and statistical analysis, a strong correlation between the grain size of the top electrode and the grain size of the HZO film has been found, suggesting that the grain size of the top electrode can induce the formation of the grain size in HZO thin films. Finally, the first-principles calculation is carried out to understand the impact of the strain and grain size on the ferroelectric properties of HZO films. The results show that the strain is the dominant factor for ferroelectricity when the grain size is large (>10 nm). However, when the grain size becomes thinner (<10 nm), the regulation effect of grain sizes increases significantly, which could bring a series of benefits for device scaling, such as device-to-device variations, film uniformity, and domain switch consistency. This work not only completes the understanding of ferroelectricity through top electrode modulation but also provides strong support for the precise regulation of ferroelectricity of nanoscale devices and ultrathin HZO ferroelectric films.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Understanding the Effect of Top Electrode on Ferroelectricity in Atomic Layer Deposited Hf_0.5Zr_0.5O₂ Thin Films

Wang

Wen

et al. 2023

ACS Appl. Mater. Interfaces

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“…Ferroelectrics based on hafnia, such as doped HfO 2 − and Hf 0.5 Zr 0.5 O 2 , − are quite unusual compared with conventional perovskite ferroelectrics. − First of all, though these oxides consist of mixed ionic-covalent bonding, it is unclear whether the covalence should play any role in the ferroelectricity. On the other hand, in perovskite oxide ferroelectrics, the existence of orbital hybridization and covalent bonding is important for the ferroelectric distortion .…”

Section: Introductionmentioning

confidence: 99%

Ferroelectricity in HfO₂ from a Coordination Number Perspective

et al. 2022

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Ferroelectricity observed in thin-film HfO 2 , either doped with Si, Al, and so forth or in the Hf 0.5 Zr 0.5 O 2 form, has gained great technical significance. While a trilinear coupling between phonon modes could explain its ferroelectric distortion, from a practical perspective, one may be concerned with a theory that is more straightforward to predict similar ferroelectric candidates through some apparent features of HfO 2 and ZrO 2 . In this work, we propose that the 7 cation coordination number of HfO 2 /ZrO 2 lies at the heart of this ferroelectricity, which stems from the proper ionic radii of Hf/Zr compared with O. Among the numerous compounds with a non-centrosymmetric nature, for example, the mm2 point group, HfO 2 and ZrO 2 are special in that they are close to the border of 7 and 8 cation coordination, such that the 8-coordination tetragonal intermediate phase could greatly reduce the switching barrier. Other 7-coordination candidates, including SrI 2 , TaON, YSBr, and YOF, are also studied in comparison to HfO 2 /ZrO 2 , and six switching paths are analyzed in detail for the Pca2 1 phase. A rule of the preferred switching path in terms of the ionic radii ratio and coordination number has been established. We also show the possible route from the ferroelectric Pca2 1 phase to the monoclinic P2 1 /c phase in HfO 2 , which is relevant to the fatigue phenomenon.

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Ferroelectric Transistors for Memory and Neuromorphic Device Applications

Kim

Lee

2023

Advanced Materials

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Because a non-centrosymmetric crystal structure is mandatory for ferroelectric properties, very few materials are classified as ferroelectric. Historically, materials with complex crystal structures, such as BaTiO 3 (BTO), Pb[Zr x Ti 1−x ]O 3 (PZT), and Sr 2 Bi 2 TaO 9 (SBT), have been found to exhibit ferroelectricity. [5][6][7][8][9] Due to their spontaneous polarization, ferroelectric materials are diversely applied in memory devices, actuators, sensors, and energy storage. [1,2,[10][11][12][13] As the polarization state of ferroelectric materials can be regulated by an external electric field and the polarization is retained after the removal of the external electric field, such materials have the potential for applications involving high-performance non volatile memories. [9,14] However, some issues of conventional ferroelectric materials, such as high annealing temperatures, the requirement of noble electrode materials, and the diffusion of elements such as Pb complicate the integration of the previously reported ferroelectric materials into complementary metal-oxide semiconductors (CMOSs). [15][16][17][18] Furthermore, the large dielectric constants of perovskite-based ferroelectrics lead to high depolarization fields; [9,16] thus, the materials have short retention time and exhibit unstable polarization. [9] Additionally, the limited thickness scalability, complex etching process, and fatigue behaviors of perovskite-based ferroelectrics hinder the development of highly scaled ferroelectric devices. [9,18] Thus, semiconductor devices based on ferroelectric materials have limited commercial applications. Since the development of hafnia-based ferroelectrics, ferroelectric hafnia has attracted immense attention toward the development of semiconductor devices. [19][20][21] Compared to perovskite-based ferroelectric materials, hafnia-based ferroelectrics exhibit high scalability, and have high coercive electric fields (E c ) and low dielectric permittivity values, making them suitable for the fabrication of high-performance memory devices. [2,16,20,22] Additionally, hafnia is compatible with Si-based CMOS processes. Due to these advantages, hafnia-based ferroelectrics have been used in next-generation memory devices (such as ferroelectric capacitors, transistors, and tunnel junctions [FTJs]). [22][23][24][25][26] This paper reviews the recent findings and applications of hafnia-based ferroelectrics, highlighting the recent advances in ferroelectric transistors for next-generation memory and neuromorphic Ferroelectric materials have been intensively investigated for highperformance nonvolatile memory devices in the past decades, owing to their nonvolatile polarization characteristics. Ferroelectric memory devices are expected to exhibit lower power consumption and higher speed than conventional memory devices. However, non-complementary metal-oxidesemiconductor (CMOS) compatibility and degradation due to fatigue of traditional perovskite-based ferroelectric materials have hindered the development of high-density...

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Constructing a correlation between ferroelectricity and grain sizes in Hf_0.5Zr_0.5O₂ ferroelectric thin films

Abstract: The correlation between ferroelectricity and grain sizes in atomic layer deposition (ALD) derived Hf0.5Zr0.5O2 (HZO) thin films has been demonstrated through controlling process conditions. The influence of annealing temperature, annealing...

Cited by 25 publications

References 46 publications

Understanding the Effect of Top Electrode on Ferroelectricity in Atomic Layer Deposited Hf_0.5Zr_0.5O₂ Thin Films

Understanding the Effect of Top Electrode on Ferroelectricity in Atomic Layer Deposited Hf_0.5Zr_0.5O₂ Thin Films

Ferroelectricity in HfO₂ from a Coordination Number Perspective

Ferroelectric Transistors for Memory and Neuromorphic Device Applications

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Constructing a correlation between ferroelectricity and grain sizes in Hf0.5Zr0.5O2 ferroelectric thin films

Abstract: The correlation between ferroelectricity and grain sizes in atomic layer deposition (ALD) derived Hf0.5Zr0.5O2 (HZO) thin films has been demonstrated through controlling process conditions. The influence of annealing temperature, annealing...

Cited by 25 publications

References 46 publications

Understanding the Effect of Top Electrode on Ferroelectricity in Atomic Layer Deposited Hf0.5Zr0.5O2 Thin Films

Understanding the Effect of Top Electrode on Ferroelectricity in Atomic Layer Deposited Hf0.5Zr0.5O2 Thin Films

Ferroelectricity in HfO2 from a Coordination Number Perspective

Ferroelectric Transistors for Memory and Neuromorphic Device Applications

Contact Info

Product

Resources

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Constructing a correlation between ferroelectricity and grain sizes in Hf_0.5Zr_0.5O₂ ferroelectric thin films

Understanding the Effect of Top Electrode on Ferroelectricity in Atomic Layer Deposited Hf_0.5Zr_0.5O₂ Thin Films

Understanding the Effect of Top Electrode on Ferroelectricity in Atomic Layer Deposited Hf_0.5Zr_0.5O₂ Thin Films

Ferroelectricity in HfO₂ from a Coordination Number Perspective