Effect of residual impurities on polarization switching kinetics in atomic-layer-deposited ferroelectric Hf0.5Zr0.5O2 thin films

Lee, Dong Hoon; Yu, Geun Taek; Park, Ju Yong; Kim, Se Hyun; Yang, Kyounghoon; Park, Geun Hyeong; Ryu, Jin Ju; Lee, Je In; Kim, Gon−Ho; Park, Min Hyuk

doi:10.1016/j.actamat.2021.117405

Cited by 20 publications

(14 citation statements)

References 63 publications

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“…Similar observations were made by Chernikova et al 64 on La-doped HZO grown on Ru, where a faster wake-up was observed when the grains favored an o(002) orientation. 65 To summarize, the prolonged wake-up observed in thinner (∼9.5 nm) films up to ∼1 × 10 6 -1 × 10 7 cycles could be caused by a corroboration of several factors: a stronger pinning effect due to the larger amount of grain boundaries at a smaller grain size, 42,66 more grains containing unfavorable orientation of ferroelectric domains with a gradual substitution of La by Y, and a higher density of oxygen vacancies that requires more switching cycles for their redistribution. A completion of the wake-up stage is indicated by a plateau in 2Pr values between ∼1 × 10 7 and ∼1 × 10 9 cycles in the case of (Y, La) co-doped HZO and Y-doped HZO.…”

Section: ■ Results and Discussionmentioning

confidence: 95%

High-Endurance Ferroelectric (La, Y) and (La, Gd) Co-Doped Hafnium Zirconate Grown by Atomic Layer Deposition

Popovici

Walke

Bizindavyi

et al. 2022

ACS Appl. Electron. Mater.

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Thin films based on stoichiometric hafnium zirconate doped and co-doped with La, Gd, and/or Y have been grown by atomic layer deposition on TiN electrodes. The resulting TiN−ferroelectric−TiN capacitors have shown high endurance up to 1 × 10 11 switching cycles. The simultaneous use of two dopants (Y, La) or (Gd, La) in hafnium zirconate increases the amount of orthorhombic and tetragonal phases. Fatigue-free capacitors with remnant polarization ≥15 μC/cm 2 at 1 × 10 11 endurance cycles have been obtained for dopants having an atomic fraction of about 1.2−1.8% and showing great promise as active materials for emerging memory applications.

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Section: ■ Results and Discussionmentioning

confidence: 95%

High-Endurance Ferroelectric (La, Y) and (La, Gd) Co-Doped Hafnium Zirconate Grown by Atomic Layer Deposition

Popovici

Walke

Bizindavyi

et al. 2022

ACS Appl. Electron. Mater.

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“…The effects of ALD temperature on ferroelectric HfO 2 /HZO films have been discussed by Kim et al and Lee et al, 32,33 in which a significant carbon incorporation was reported in ALD-HfO 2 or HZO films deposited at low temperature. These authors proposed that the carbon contamination caused a much smaller grain size in the final films, thus promoting the formation of o-HfO 2 .…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Nanocrystallite Seeding of Metastable Ferroelectric Phase Formation in Atomic Layer-Deposited Hafnia–Zirconia Alloys

Saini

Liu

et al. 2022

ACS Appl. Mater. Interfaces

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Hafnia-based ferroelectric thin films are promising for semiconductor memory and neuromorphic computing applications. Amorphous, as-deposited, thin-film binary alloys of HfO 2 and ZrO 2 transform to the metastable, orthorhombic ferroelectric phase during post-deposition annealing and cooling. This transformation is generally thought to involve formation of a tetragonal precursor phase that distorts into the orthorhombic phase during cooling. In this work, we systematically study the effects of atomic layer deposition (ALD) temperature on the ferroelectricity of post-deposition-annealed Hf 0.5 Zr 0.5 O 2 (HZO) thin films. Seed crystallites having interplanar spacings consistent with the polar orthorhombic phase are observed by a plan-view transmission electron microscope in HZO thin films deposited at an elevated ALD temperature. After ALD under conditions that promote formation of these nanocrystallites, high-polarization (P r > 18 μC/cm 2 ) ferroelectric switching is observed after rapid thermal annealing (RTA) at low temperature (350 °C). These results indicate the presence of minimal non-ferroelectric phases retained in the films after RTA when the ALD process forms nanocrystalline particles that seed subsequent formation of the polar orthorhombic phase.

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“…Some research groups reported that polymorphism in HfO 2 and HZO is strongly influenced by the defect concentration 21,66,67 . Lee et al recently demonstrated that increased defect concentration increased the distribution of the nucleation time in nucleation‐limited switching (NLS) in HZO thin films 68 . However, the inhomogeneous distribution of chemical impurities can be improved by process optimization, and oxygen vacancies have a special role here.…”

Section: Advantages and Challenges Of Fluorite‐structured Ferroelectr...mentioning

confidence: 99%

“…The KAI and NLS models are representative models for describing polarization switching kinetics 77–81 . The growth of the domain in fluorite‐structured ferroelectrics deposited using ALD is limited to a narrow region because of its polycrystalline nature with diverse defects, such as grain boundaries and impurities 19,68,87,135 . Therefore, the growth time can be neglected, and the nucleation waiting time limits the total polarization reversal time.…”

Section: Neuromorphic Computing Systems Based On Fluorite‐structured ...mentioning

confidence: 99%

“…21,66,67 Lee et al recently demonstrated that increased defect concentration increased the distribution of the nucleation time in nucleation-limited switching (NLS) in HZO thin films. 68 However, the inhomogeneous distribution of chemical impurities can be improved by process optimization, and oxygen vacancies have a special role here. These oxygen vacancies help to stabilize the ferroelectric phase, while concurrently causing reliability issues such as cycling instabilities and imprint.…”

Section: Advantages and Challenges Of Nonvolatile Memorymentioning

confidence: 99%

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Neuromorphic devices based on fluorite‐structured ferroelectrics

Lee

Park

Kim

et al. 2022

InfoMat

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A continuous exponential rise has been observed in the storage and processing of the data that may not curtail in the foreseeable future. The required data processing speed and power consumption are restricted by the buses between the logic and memory devices that are characteristic of the von Neumann computing architecture. Bio-mimicking neuromorphic computing has garnered considerable academic and industrial interest to resolve these challenges.Additionally, devices based on emerging nonvolatile memories capable of mimicking the behaviors of synapses and neurons, which are the main elements in biological computing systems (brains), are attracting significant interest from the device community. With the discovery of ferroelectricity in fluorite-structured oxides, such as HfO 2 and ZrO 2 , which are compatible with the state-of-the-art complementary-metal-oxide-semiconductor processes, ferroelectric devices have rapidly evolved as the main direction of these research and development activities. Fundamental science related to fluorite-structured ferroelectrics has been intensively studied over the last decade. At present, the focus is gradually moving to practical applications, including neuromorphic computing and advanced classical processing or memory units in the conventional von Neumann architecture. However, despite its rapid development, the wealth of recent progress in neuromorphic computing devices based on fluorite-structured ferroelectrics has not been reviewed and systemized. This progress report comprehensively reviews and systemizes the recent progress in artificial synaptic and spiking neuron devices for neuromorphic computing based on fluorite-structured ferroelectrics.

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Effect of residual impurities on polarization switching kinetics in atomic-layer-deposited ferroelectric Hf0.5Zr0.5O2 thin films

Cited by 20 publications

References 63 publications

High-Endurance Ferroelectric (La, Y) and (La, Gd) Co-Doped Hafnium Zirconate Grown by Atomic Layer Deposition

High-Endurance Ferroelectric (La, Y) and (La, Gd) Co-Doped Hafnium Zirconate Grown by Atomic Layer Deposition

Nanocrystallite Seeding of Metastable Ferroelectric Phase Formation in Atomic Layer-Deposited Hafnia–Zirconia Alloys

Neuromorphic devices based on fluorite‐structured ferroelectrics

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