Review on the Microstructure of Ferroelectric Hafnium Oxides

Lederer, Maximilian; Lehninger, David; Ali, Tarek; Kämpfe, Thomas

doi:10.1002/pssr.202200168

Cited by 19 publications

(18 citation statements)

References 167 publications

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“…Reports of interfacial/gradual RS in many other materials systems were based on complex perovskites (16), which are not industrycompatible, or they relied on the incorporation of other industryincompatible materials in otherwise compatible oxides, such as Pt nanoparticles dispersed in SiO 2 (17). Compared with other industry-compatible oxides where gradual/interfacial RS has been demonstrated, for example TiO x (18) or TaO x (19), hafnium oxide offers the additional versatility of having ferroelectric (FE) (crystalline) phases (20), which may provide an additional edge among the competition for future memory and neuromorphic devices. Furthermore, the focus of many reports is often on individual device demonstrations, but it is important to achieve and report uniform performance beyond single devices (21).…”

Section: Introductionmentioning

confidence: 99%

Thin film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity

et al. 2023

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A design concept of phase-separated amorphous nanocomposite thin films is presented that realizes interfacial resistive switching (RS) in hafnium oxide–based devices. The films are formed by incorporating an average of 7% Ba into hafnium oxide during pulsed laser deposition at temperatures ≤400°C. The added Ba prevents the films from crystallizing and leads to ∼20-nm-thin films consisting of an amorphous HfO x host matrix interspersed with ∼2-nm-wide, ∼5-to-10-nm-pitch Ba-rich amorphous nanocolumns penetrating approximately two-thirds through the films. This restricts the RS to an interfacial Schottky-like energy barrier whose magnitude is tuned by ionic migration under an applied electric field. Resulting devices achieve stable cycle-to-cycle, device-to-device, and sample-to-sample reproducibility with a measured switching endurance of ≥10 4 cycles for a memory window ≥10 at switching voltages of ±2 V. Each device can be set to multiple intermediate resistance states, which enables synaptic spike-timing–dependent plasticity. The presented concept unlocks additional design variables for RS devices.

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Section: Introductionmentioning

confidence: 99%

Thin film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity

et al. 2023

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“…In addition to the deposition process parameters, the thermal budget can also influence the crystal structure of HfO 2 -based films . The crystal phase of the HfO 2 -based system during the thermal treatment usually develops from amorphous into the crystalline t-phase and later to o-phase and m-phase. − Sufficient thermal energy could help the HZO film to overcome the energy barrier for transformation from the t-phase to the o-phase. In the meanwhile, excessive energy could enhance the transition from the t-phase to the m-phase. − After annealing at 800 °C, the samples processed at 5 × 10 –3 mbar showed higher 2 P r , which suggests a higher polar o-phase fraction.…”

Section: Resultsmentioning

confidence: 99%

Sputtered Ferroelectric Hafnium–Zirconium Oxide with High Remanent Polarization after Back-End-of-Line Compatible Annealing

Wang

Mikolajick

Grube

2022

ACS Appl. Electron. Mater.

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The back-end-of-line (BEOL) processing compatibility of sputtered ferroelectric hafnium zirconium oxide (HZO) thin films is demonstrated on sputtered TiN/HZO/TiN thin-film ferroelectric capacitors. This promises an easy integration of HfO2-based ferroelectrics for applications such as non-volatile memories. It is found that the sputtering pressure can significantly influence the film growth and morphology of HZO layers. At a sputtering pressure of 5 × 10–3 mbar, deposited HZO films show high remanent polarization (P r) after 400 °C annealing, indicating a high fraction of the polar orthorhombic crystal structure. Additionally, the ferroelectric properties of HZO films were improved by proper tuning of sputtering power. We are able to show that a BEOL-compatible thermal budget (at 400 °C for 1 h) is enough to provoke good ferroelectricity with the 2P r of up to 36 μC/cm2 and an endurance of up to 107 cycles in sputtered HZO films. With such modifications, the sputtered HZO films become comparable to atomic-layer deposited HZO films with a similar thermal budget.

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“…Domain wall motion is of particular interest in fluorite structures such as HfO 2 , since such structures do not contain Ising walls as in perovskites, but instead domains down to the size of a unit cell with highly localized domain walls . This is possible due to flat phonon bands, which suppress an interaction between the dipoles and thus make them locally switchable .…”

Section: Introductionmentioning

confidence: 99%

Domain Wall Movement in Undoped Ferroelectric HfO₂: A Rayleigh Analysis

Marquardt

Petersen

Gronenberg

et al. 2023

ACS Appl. Electron. Mater.

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The discovery of ferroelectricity in doped HfO2 in 2011 gave rise to quite a stir in the scientific world that persists up to this day. The complementary metal oxide semiconductor compatibility, as well as good scalability, enables versatile applications ranging from ferroelectric field effect transistors to ferroelectric tunnel junctions and neuromorphic devices. Stabilizing the metastable polar orthorhombic phase with space group Pca21-phase, which is responsible for the ferroelectricity in HfO2, is still challenging. We demonstrate for the first time a sputter deposition of undoped ferroelectric HfO2 on superconducting NbN electrodes, with a remanent polarization of 6.4 μC/cm2. Grazing incident X-ray diffraction on the layer structure, dynamic hysteresis measurements, and electron energy loss spectroscopy on fabricated devices indicate a HfO2 layer with low oxygen deficiency. Furthermore, no evidence of interdiffusion of oxygen or nitrogen at the interfaces is found. A sudden “wake-up” for the transition from the dielectric state to the ferroelectric state as well as no classical fatigue effect for the degradation of the ferroelectric performance are observed. These analyses are extended by an investigation of Rayleigh behavior using impedance spectroscopy. In that way, the domain wall flexibility is quantified and classified within different regimes of the various domain wall motions.

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Review on the Microstructure of Ferroelectric Hafnium Oxides

Cited by 19 publications

References 167 publications

Thin film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity

Thin film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity

Sputtered Ferroelectric Hafnium–Zirconium Oxide with High Remanent Polarization after Back-End-of-Line Compatible Annealing

Domain Wall Movement in Undoped Ferroelectric HfO₂: A Rayleigh Analysis

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Review on the Microstructure of Ferroelectric Hafnium Oxides

Cited by 19 publications

References 167 publications

Thin film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity

Thin film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity

Sputtered Ferroelectric Hafnium–Zirconium Oxide with High Remanent Polarization after Back-End-of-Line Compatible Annealing

Domain Wall Movement in Undoped Ferroelectric HfO2: A Rayleigh Analysis

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Domain Wall Movement in Undoped Ferroelectric HfO₂: A Rayleigh Analysis