Ferroelectric Zr0.5Hf0.5O2 thin films for nonvolatile memory applications

Müller, Johannes; Böscke, T. S.; Bräuhaus, D.; Schröder, Uwe; Böttger, U.; Sundqvist, Jonas; Kücher, Peter; Mikolajick, Thomas; Frey, L.

doi:10.1063/1.3636417

Cited by 487 publications

(299 citation statements)

References 14 publications

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“…To assess the phase stability at a finite temperature T and entropy S, we calculated the Helmholtz free energy F as F = U -TS (2) from the phonon contribution by integrating over the phonon density of state. …”

Section: H Elm Holtz Free Energymentioning

confidence: 99%

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

Materlik

Kuenneth

Kersch

2015

Journal of Applied Physics

661

684

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The structural, thermal, and dielectric properties of the ferroelectric phase of HfO2, ZrO2 and Hf0.5Zr0.5O2 (HZO) are investigated with carefully validated density functional computations.We find, that the free bulk energy of the ferroelectric orthorhombic Pca21 phase is unfavorable compared to the monoclinic P21/c and the orthorhombic Pbca phase for all investigated stoichiometries in the HfχZr1-χO2 system. To explain the existence of the ferroelectric phase in nanoscale thin films we explore the Gibbs / Helmholtz free energies as a function of stress and film strain and find them unlikely to become minimal in HZO films for technological relevant conditions. To assess the contribution of surface energy to the phase stability we parameterize a model, interpolating between existing data, and find the Helmholtz free energy of ferroelectric grains minimal for a range of size and stoichiometry. From the model we predict undoped HfO2 to be ferroelectric for a grain size of about 4 nm and epitaxial HZO below 5 nm.Furthermore we calculate the strength of an applied electric field necessary to cause the

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Section: H Elm Holtz Free Energymentioning

confidence: 99%

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

Materlik

Kuenneth

Kersch

2015

Journal of Applied Physics

661

684

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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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“…Recently, it has been demonstrated that doping of HfO 2 thin films with SiO 2 5 or ZrO 2 6 does not only stabilizes the tetragonal phase, but can also produce a spontaneous polarization at intermediate doping levels, that results in usable, ferroelectric hysteresis loops in these layers.…”

Section: Introductionmentioning

confidence: 99%

Ferroelectricity in yttrium-doped hafnium oxide

Müller

Schröder

Böscke³

et al. 2011

Journal of Applied Physics

Self Cite

582

351

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Structural incommensurate modulation rule in hexagonal Ba(Ti1-xMx)O3-δ (M = Mn, Fe) multiferroics AIP Advances 2, 042129 (2012) Water assisted gate induced temporal surface charge distribution probed by electrostatic force microscopy J. Appl. Phys. 112, 084329 (2012) Influence of target composition and deposition temperature on the domain structure of BiFeO3 thin films AIP Advances 2, 042104 (2012) Nanodomain structures formation during polarization reversal in uniform electric field in strontium barium niobate single crystals J. Appl. Phys. 112, 064117 (2012) The effect of the top electrode interface on the hysteretic behavior of epitaxial ferroelectric Pb(Zr,Ti)O3 thin films with bottom SrRuO3 electrode J. Appl. Phys. 112, 064116 (2012) Additional information on J. Appl. Phys. Structural and electrical evidence for a ferroelectric phase in yttrium doped hafnium oxide thin films is presented. A doping series ranging from 2.3 to 12.3 mol% YO 1.5 in HfO 2 was deposited by a thermal atomic layer deposition process. Grazing incidence X-ray diffraction of the 10 nm thick films revealed an orthorhombic phase close to the stability region of the cubic phase. The potential ferroelectricity of this orthorhombic phase was confirmed by polarization hysteresis measurements on titanium nitride based metal-insulator-metal capacitors. For 5.2 mol% YO 1.5 admixture the remanent polarization peaked at 24 lC=cm 2 with a coercive field of about 1.2 MV=cm. Considering the availability of conformal deposition processes and CMOS-compatibility, ferroelectric Y:HfO 2 implies high scaling potential for future, ferroelectric memories.

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Ferroelectric Zr0.5Hf0.5O2 thin films for nonvolatile memory applications

Cited by 487 publications

References 14 publications

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

Ferroelectric HfO₂-based materials for next-generation ferroelectric memories

Ferroelectricity in yttrium-doped hafnium oxide

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Ferroelectric Zr0.5Hf0.5O2 thin films for nonvolatile memory applications

Cited by 487 publications

References 14 publications

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

Ferroelectric HfO2-based materials for next-generation ferroelectric memories

Ferroelectricity in yttrium-doped hafnium oxide

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Product

Resources

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Ferroelectric HfO₂-based materials for next-generation ferroelectric memories