Wake-up effects in Si-doped hafnium oxide ferroelectric thin films

Zhou, Dayu; Xu, Jie; Li, Qing; Guan, Yan; Cao, Fei; Dong, Xianlin; Müller, Johannes; Schenk, Tony; Schröder, Uwe

doi:10.1063/1.4829064

Cited by 346 publications

(278 citation statements)

References 21 publications

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“…8 We observed that a definite amount of wake-up cycles is required to enhance the hysteresis and P r as well as E C in these films. Our results were found to be in agreement with the previously published reports by Zhou et al 13 in ALD deposited Si-doped HfO 2 thin films and later on by Starschich et al 11 in chemical solution deposited Y-doped HfO 2 thin films, where the "wake-up" effect in the polarization hysteresis was observed. The "wake-up" (deaging) effect corresponds to an increase in the remnant polarization caused by the application of subsequent bipolar voltage cycles.…”

Section: Methodssupporting

confidence: 83%

“…17 These charged defects near the electrode/ferroelectric interface inhibit the growth of domains of opposite polarity. 13 High interfacial charged defects can lead to the band banding with the formation of a depletion layer where the built-in electric field (E bi ) across the depletion region can be expected to result in local alignment of ferroelectric dipoles. 2 Further, successive bipolar voltage cycles can cause removal or redistribution of these charged defects, which reduces the E bi by de-pinning more and more domains to participate in polarization switching.…”

Section: Methodsmentioning

confidence: 99%

“…On the other hand, in some of the reports, ferroelectric nature in doped-HfO 2 films was attributed to the influence of "wake-up" effect. [11][12][13] In this paper, we report on the ferroelectric properties of rare earth doped Sm:HfO 2 (SHO) and Gd:HfO 2 (GHO) thin films fabricated by the sequential pulsed laser deposition (SPLD) technique. [14][15][16] The deposition was performed by periodic depositions from HfO 2 and Sm 2 O 3 /Gd 2 O 3 ceramic targets.…”

mentioning

confidence: 99%

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Ferroelectricity in Rare-Earth Modified Hafnia Thin Films Deposited by Sequential Pulsed Laser Deposition

Sharma

Barrionuevo

Agarwal

et al. 2015

ECS Solid State Letters

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Room temperature ferroelectricity in pulsed laser deposited rare-earth doped hafnium oxide (HfO 2 ) thin films is discussed. Maximum values of remnant polarizations (P r ) ∼13.5 and 12 μC/cm 2 along with coercive fields (E C ) ∼334 and 384 kV/cm are observed in 6 mol. % of rare-earth (Sm or Gd) doped-HfO 2 thin films (Sm:HfO 2 and Gd:HfO 2 ), respectively. Piezoresponse force microscopy measurements confirmed ferroelectric nature of films by showing phase hysteresis and butterfly amplitude loops. It is noticed that wake-up cycles improved the remnant polarization and found to be necessary for the forming of well saturated hysteresis loops. Our results showed potential toward realization of future highly scaled non-volatile ferroelectric memories. Ferroelectric materials are engendering considerable interest because of a variety of emerging applications including ferroelectric memories which have promising potentials for next generation high integration density and low power nonvolatile memory technology. 1,2The most studied material for ferroelectric memories, Pb[Zr x Ti 1-x ]O 3 (PZT), 1 is facing severe scaling limitations due to its complicated crystal structure which in turn hinders its applicability toward dense integration in the complementary metal oxide semiconductor (CMOS) technology. The lead (Pb) toxicity in PZT is also a snag due to ecological concerns.Recently, experimental as well as theoretical studies showed ferroelectricity in doped hafnia (HfO 2 ) thin films which are compatible with existing CMOS technology.3-10 Ferroelectric phenomenon in these doped-HfO 2 films deposited by various deposition techniques such as atomic layer deposition, 5-10 chemical solution deposition, 11 and sputtering 12 was mainly explained by the existence of noncentrosymmetric orthorhombic phase (space group of Pca2 1 ). 5,6,12 The dopant incorporation into monoclinic HfO 2 matrix results in a transformation to tetragonal/cubic phase with the appearance of an intermediate metastable orthorhombic (Pca2 1 ) phase. On the other hand, in some of the reports, ferroelectric nature in doped-HfO 2 films was attributed to the influence of "wake-up" effect. [11][12][13] In this paper, we report on the ferroelectric properties of rare earth doped Sm:HfO 2 (SHO) and Gd:HfO 2 (GHO) thin films fabricated by the sequential pulsed laser deposition (SPLD) technique. [14][15][16] The deposition was performed by periodic depositions from HfO 2 and Sm 2 O 3 /Gd 2 O 3 ceramic targets. The dopant concentration was obtained by controlling number of Sm 2 O 3 /Gd 2 O 3 ablation pulses relative to that of HfO 2 . To study the ferroelectric properties of the deposited samples, polarization-voltage (P-V), capacitance-voltage (C-V), and piezoresponse force microscopy (PFM) measurements were performed. ExperimentalPolycrystalline thin films of SHO and GHO of ∼60 nm thickness were fabricated on Pt/TiO 2 /SiO 2 /Si substrates by SPLD technique at a fixed temperature of 650• C and in an oxygen ambient partial pressure of ∼0.5 Pa. The KrF excimer laser...

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Section: Methodssupporting

confidence: 83%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Ferroelectricity in Rare-Earth Modified Hafnia Thin Films Deposited by Sequential Pulsed Laser Deposition

Sharma

Barrionuevo

Agarwal

et al. 2015

ECS Solid State Letters

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“…In this connection, anisotropic stresses are required for the phase transition from tetragonal to orthorhombic, i.e., a compressive stress within the aob plane and a tensile stress along the c-axis exerted on the t-phase. There are many factors reported hitherto to be responsible for causing the anisotropic stresses and thus stabilizing the ferroelectric o-phase during the film growth, such as doping, 4,5,[23][24][25][26][27][28][29][30][31][32][33][34][35] surface energy effect, [36][37][38] island coalescence, 39 thermal expansion mismatch, 17 capping layer effect, 4,38 and formation of oxygen vacancies. 40 The following of this section will discuss each of these factors in order.…”

Section: Origins Of Ferroelectricity In Hfo 2 -Based Materialsmentioning

confidence: 99%

Ferroelectric HfO₂-based materials for next-generation ferroelectric memories

2016

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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.

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“…2,3 Cathodoluminescence due to oxygen vacancies was also recently found in ion beam sputtered HfO 2 and first steps toward fabrications of hafnia micro-light emitting devices were already taken. 4,5 The resistance switching behavior due to formation and rupture of conductive paths within HfO 2 deposited by atomic layer deposition was exploited for random access memory fabrication.…”

mentioning

confidence: 99%

Anodization Behavior of Glassy Metallic Hafnium Thin Films

Mardare

Siket

Gavrilović-Wohlmuther

et al. 2015

J. Electrochem. Soc.

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Glassy metallic Hf thin films were obtained using electron beam deposition at room temperature due to the low energy received by Hf atoms during the film formation process. The amorphous nature of the Hf films suggested by XRD was confirmed by low temperature electrical conductivity measurements where a negative temperature coefficient of resistivity was identified. Anodic oxidations using a scanning droplet cell microscopy were performed on a typical crystalline (hexagonal) Hf film obtained by sputtering and on the glassy Hf. A decrease of the oxide formation factor by 30% (from 2.4 to 1.7 nm V −1 ) was evidenced on the amorphous Hf. Electrochemical impedance spectroscopy on both samples revealed almost identical capacitances while the electrical permittivities were found to differ by 40%. The dielectric constant of the HfO 2 decreased from 33.5 on the crystalline parent metal sample to 19.8 on the amorphous one. The unexpected 10% deviation was attributed to a smoother defect-free oxide/metal interface in the case of Hafnium dioxide has a high dielectric constant, a relatively large bandgap, larger heat of formation as compared to SiO 2 , good chemical and thermal stability on Si and large barrier heights at interfaces with Si. Its modern applications are diverse, most recent ones focused on electronic devices. The chosen methods for obtaining hafnia thin films are also varied, most common one being reactive sputtering.1 Doping of sputtered hafnia with elements such as Ce has led to an increase in the dielectric constant and a decrease of the leakage currents, while Si doping revealed intrinsic ferroelectricity due to a non-centrosymmetric orthorhombic phase with direct applications in ferroelectric memories.2,3 Cathodoluminescence due to oxygen vacancies was also recently found in ion beam sputtered HfO 2 and first steps toward fabrications of hafnia micro-light emitting devices were already taken. 4,5 The resistance switching behavior due to formation and rupture of conductive paths within HfO 2 deposited by atomic layer deposition was exploited for random access memory fabrication. 6 Since these are only a few examples of most recent applications of HfO 2 , still the predominant effort is put into using it as high-k material for gate oxides for replacing SiO 2 gates in MOS-FET structures.7 For a typical operation voltage of 1-1.5 V, the leakage current through HfO 2 dielectric films was found to be several orders of magnitude lower than that of SiO 2 for the same equivalent oxide thickness of 0.9-2 nm.8-10 However, clearly a weak point in using thermally grown or vapour phase deposited HfO 2 as gate dielectrics arises from its poor interfacing with semiconductors which has led to a fervent investigation of hafnium-based complex oxides in recent years. 7Nowadays it is common knowledge that the anodic oxides on valve metals (e.g. Al, Hf, Ta, Nb etc.) are some of the most compact oxides available due to their growth mechanism obeying a high field regime.11 However, their use for electronic devices is weakly ex...

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Wake-up effects in Si-doped hafnium oxide ferroelectric thin films

Cited by 346 publications

References 21 publications

Ferroelectricity in Rare-Earth Modified Hafnia Thin Films Deposited by Sequential Pulsed Laser Deposition

Ferroelectricity in Rare-Earth Modified Hafnia Thin Films Deposited by Sequential Pulsed Laser Deposition

Ferroelectric HfO₂-based materials for next-generation ferroelectric memories

Anodization Behavior of Glassy Metallic Hafnium Thin Films

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Wake-up effects in Si-doped hafnium oxide ferroelectric thin films

Cited by 346 publications

References 21 publications

Ferroelectricity in Rare-Earth Modified Hafnia Thin Films Deposited by Sequential Pulsed Laser Deposition

Ferroelectricity in Rare-Earth Modified Hafnia Thin Films Deposited by Sequential Pulsed Laser Deposition

Ferroelectric HfO2-based materials for next-generation ferroelectric memories

Anodization Behavior of Glassy Metallic Hafnium Thin Films

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Product

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Ferroelectric HfO₂-based materials for next-generation ferroelectric memories