Low-Voltage Permittivity Control of Coplanar Lines Based on Hafnium Oxide Ferroelectrics Grown on Silicon

Aldrigo, Martino; Dragoman, Mircea; Iordanescu, S.; Nastase, F.; Vulpe, Silviu; Dinescu, Adrian; Vasilache, D.

doi:10.1109/access.2019.2942430

Cited by 9 publications

(13 citation statements)

References 29 publications

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“…At the same time, losses also increase with the DC bias (due to the increase of R IDC ), which entails a higher insertion loss. However, as demonstrated in [ 10 ], the effective loss tangent of a 6-nm-thick HfZrO thin film decreases with frequency (and increases with bias). Nevertheless, it exhibits small variations with the applied DC voltage, which entails a lowering of the dielectric losses in the ferroelectric.…”

Section: Resultsmentioning

confidence: 92%

“…The extracted curve for ε ( V ) at 10 GHz using Equations (1) and (2) is shown in Figure 4 , which was obtained by means of the Bianco–Parodi method described in [ 10 ] applied to two CPW lines of different lengths, designed on a HRSi/HfZrO substrate, and fabricated in the same run together with the structures that are presented in this work. Hence, this figure represents the value of the bias-dependent permittivity of HfZrO at a specific frequency, irrespective of the microwave device making use of a ferroelectric HfZrO thin film.…”

Section: Resultsmentioning

confidence: 99%

“…‘Traditional’ methods that are used to analyse multilayer interdigital capacitors (IDCs) or coplanar waveguide (CPW) lines (like single layer reduction or microstrip dual resonator) inevitably fail, since the nanometric scale thickness of the HfZrO ferroelectric thin film makes it impossible to apply analytical methods. Hence, starting from the results that were published in [ 10 , 12 ], via a fitting procedure exploiting electromagnetic (EM) simulations and experiments we can derive the following equation, which expresses the dependence of the relative permittivity ε ( V ) of the 6-nm-thick HfZrO on the applied voltage, at an assigned frequency: ε ( V ) = [ αV + ε eff (0)/( ε eff,bulk ) 1⁄2 ] 2 + ε eff (0), where 0 < α < 1 V −1 (which depends on the given frequency) is a characteristic constant of HfZrO, whereas ε eff (0) is the effective permittivity at 0 V of the HfZrO/bulk substrate, and ε eff,bulk is the effective permittivity of the sole bulk substrate. In terms of electric fields: ε ( V ) = [ α ( E a − E c ) t + ε eff (0)/( ε eff,bulk ) 1⁄2 ] 2 + ε eff (0), where t is the thickness of the HfZrO thin film, E a is the external applied DC electric field, and E c is the coercive field (i.e., 1–2 MV/cm for HfZrO).…”

Section: Methodsmentioning

confidence: 99%

“…In terms of electric fields: ε ( V ) = [ α ( E a − E c ) t + ε eff (0)/( ε eff,bulk ) 1⁄2 ] 2 + ε eff (0), where t is the thickness of the HfZrO thin film, E a is the external applied DC electric field, and E c is the coercive field (i.e., 1–2 MV/cm for HfZrO). Equation (2) is derived in a straightforward way from Equation (1), while taking into account that the DC voltage that is applied to the HfZrO thin film is physically determined by both the external contribution of E a (which can be estimated also by static EM simulations [ 10 , 12 ]) and the intrinsic contribution of E c , in order to describe the hysteretic behaviour of the permittivity. These simple relations fit well with the experimental results, if one knows ε eff (0) and ε eff,bulk (at the desired frequency) that can be easily obtained by either theoretical/simulation results or measurements of scattering parameters.…”

Section: Methodsmentioning

confidence: 99%

“…The answer is positive, since, in any ferroelectric, there is a strong dependency of electrical permittivity on the applied voltage, this property being used extensively in the case of high-frequency devices for tuning their main characteristics [ 9 ]. We have recently shown that, in a very large band (1–8 GHz), there is an increase of 27% of the permittivity of HfZrO when a DC bias voltage is swept in the range 0–5 V [ 10 ]. Based on these results, the aim of this paper is to show that we can tune the reflection (|S 11 | or |S 22 |) and transmission (|S 21 | or |S 12 |) coefficients of a low-pass filter (LPF), a high-pass filter (HPF), and a band-pass filter (BPF) when the applied DC voltage is tuned in the range 0–4 V. These circuits are of outmost importance in many areas of wireless communications where filters are ubiquitous components [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

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Tunable Microwave Filters Using HfO2-Based Ferroelectrics

et al. 2020

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In this paper, we present microwave filters that are based on 6-nm-thick ferroelectric thin films of hafnium oxide doped with zirconium (HfZrO), which are tunable continuously in targeted bands of interest within the frequency range 0.1–16 GHz, when the applied direct current (DC) voltage is swept between 0 V and 4 V. Here, we exploit the orthorhombic polar phase in HfO2 through a careful doping using zirconium in an Atomic Layer Deposition (ALD) process, in order to guarantee phase stabilization at room temperature. Polarization versus voltage characterization has been carried out, showing a remanent polarization (Pr) of ~0.8 μC/cm2 and the coercive voltage at ~2.6 V. The average roughness has been found to be 0.2 nm for HfZrO films with a thickness of 6 nm. The uniform topography, without holes, and the low surface roughness demonstrate that the composition and the structure of the film are relatively constant in volume. Three filter configurations (low-pass, high-pass, and band-pass) have been designed, modelled, fabricated, and fully characterized in microwaves, showing a frequency shift of the minimum of the reflection coefficient between 90 MHz and 4.4 GHz, with a minimum insertion loss of approximately 6.9 dB in high-pass configuration.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tunable Microwave Filters Using HfO2-Based Ferroelectrics

et al. 2020

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Fluorite‐Structured Ferroelectric and Antiferroelectric Materials: A Gateway of Miniaturized Electronic Devices

Ali

Lehninger

et al. 2022

Adv Funct Materials

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Ferroelectric (FE) and antiferroelectric (AFE) materials are used for several memory-related and energy-related applications. Perovskite materials (e.g., bulk ceramics) remain the most common materials for many applications. However, due to large deposition thickness, these materials are not appropriate for future miniaturized devices. In 2011, FE and AFE properties were reported in Si-doped HfO 2 thin films. HfO 2 -based FE and AFE materials have several advantages over conventional materials, such as ultrathin deposition thickness (in range of nanometers), compatibility with existing Si semiconductor technology, and suitability for the integration within 3-D nanostructures. Therefore, fluorite-structured materials can be appropriate for miniaturized devices. These fluorite-structured materials are extensively studied for memory and energy-related applications. The first review on this topic was published after four years of discovering the FE and AFE properties in these materials. From the past decade, a lot of research has been reported about the detailed mechanism and application of these materials. This review insightfully discusses the progress in the research of fluorite-structured materials and critically discusses some potential applications. Here some challenges are also discussed, new knowledge is extracted, and promising future research directions of these materials are suggested.

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HfO₂‐Based Ferroelectrics Applications in Nanoelectronics

Dragoman

Aldrigo

Dragoman

et al. 2021

Physica Rapid Research Ltrs

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In memoriam of Prof. Dan Dascalu IntroductionHafnium oxide (HfO 2 ) is the dielectric commonly used in fieldeffect transistors (FETs) fabricated in complementary metal oxide semiconductor (CMOS) technologies and, as such, retrieved in any very large-scale integrated (VLSI) circuits. Examples of such circuits include microprocessors or complex analog integrated circuits found in daily applications, for instance, in computers, smartphones, laptops, or incorporated in cars, airplanes, or medical equipments. Since the discovery of HfO 2 as a dielectric for modern integrated circuits, increasing its permittivity was a leading research issue in itself because higher permittivity values allow decreasing the effective oxide thickness (EOT), and so the leakage current; this is especially important when billions of Si FETs are integrated on a single chip. The solution found to boost the permittivity of HfO 2 is represented by structural phase transformations. [1] HfO 2 has its lowest electrical permittivity (ε r % 18) in its stable phase, which is the monoclinic phase. Higher permittivity values, of ε r % 27 in the cubic phase and ε r % 70 in the tetragonal phase, are achieved, nonetheless, in phases that are stable only at very high temperatures, exceeding 1700 C. The decrease in these temperatures is possible, however, by HfO 2 doping. Thus, the cubic and the tetragonal phases were first obtained at lower temperatures via Y doping [1] and, respectively, Si doping, [2] whereas a stable HfO 2 tetragonal phase at nearly room temperature was observed by growing HfO 2 via atomic layer deposition (ALD) and doping it with ZrO 2 . [3,4] As described in the recent review, [5] the stabilization of these phases is determined by the concentration of dopants, the annealing temperature, and the growing methods.These initial investigations focused on increasing the permittivity of HfO 2 lead eventually to the discovery of the orthorhombic phase of HfO 2 , which was associated with HfO 2 ferroelectricity. [6,7] This phase is obtained under different growth conditions in the presence of dopants, including those mentioned earlier, and requires strict control of dopant concentration, temperature, and mechanical strain. The most used orthorhombic HfO 2 -based ferroelectric, named further as Hf ZrO, is doped with Zr and is usually grown at the wafer level, up to 300 mm, using ALD. It thus benefits from the state-of-the-art CMOS technology. More recently, using Zr-doping and pulsed laser deposition (PLD), another rhombohedral phase of HfO 2 was discovered to be also ferroelectric. [7] The rhombohedral or orthorhombic Hf ZrO are ferroelectrics with similar electric performances; the origin of stable ferroelectricity in both cases being due to the induced strain between the top and/or down substrates sandwiching Hf ZrO. [8] Doping or strain application modifies the atomic structure of a material and can induce a phase transition, in particular can induce ferroelectricity in HfO 2 . Similarly, HfO 2 can transform into a weak magnetic material [9...

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Low-Voltage Permittivity Control of Coplanar Lines Based on Hafnium Oxide Ferroelectrics Grown on Silicon

Cited by 9 publications

References 29 publications

Tunable Microwave Filters Using HfO2-Based Ferroelectrics

Tunable Microwave Filters Using HfO2-Based Ferroelectrics

Fluorite‐Structured Ferroelectric and Antiferroelectric Materials: A Gateway of Miniaturized Electronic Devices

HfO₂‐Based Ferroelectrics Applications in Nanoelectronics

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Low-Voltage Permittivity Control of Coplanar Lines Based on Hafnium Oxide Ferroelectrics Grown on Silicon

Cited by 9 publications

References 29 publications

Tunable Microwave Filters Using HfO2-Based Ferroelectrics

Tunable Microwave Filters Using HfO2-Based Ferroelectrics

Fluorite‐Structured Ferroelectric and Antiferroelectric Materials: A Gateway of Miniaturized Electronic Devices

HfO2‐Based Ferroelectrics Applications in Nanoelectronics

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Product

Resources

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HfO₂‐Based Ferroelectrics Applications in Nanoelectronics