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29 pages, 4052 KB

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Structural and Insulating Behaviour of High-Permittivity Binary Oxide Thin Films for Silicon Carbide and Gallium Nitride Electronic Devices

by Raffaella Lo Nigro, Patrick Fiorenza, Giuseppe Greco, Emanuela Schilirò and Fabrizio Roccaforte

Materials 2022, 15(3), 830; https://doi.org/10.3390/ma15030830 - 22 Jan 2022

Cited by 30 | Viewed by 8431

Abstract

High-κ dielectrics are insulating materials with higher permittivity than silicon dioxide. These materials have already found application in microelectronics, mainly as gate insulators or passivating layers for silicon (Si) technology. However, since the last decade, the post-Si era began with the pervasive introduction of wide band gap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), which opened new perspectives for high-κ materials in these emerging technologies. In this context, aluminium and hafnium oxides (i.e., Al₂O₃, HfO₂) and some rare earth oxides (e.g., CeO₂, Gd₂O₃, Sc₂O₃) are promising high-κ binary oxides that can find application as gate dielectric layers in the next generation of high-power and high-frequency transistors based on SiC and GaN. This review paper gives a general overview of high-permittivity binary oxides thin films for post-Si electronic devices. In particular, focus is placed on high-κ binary oxides grown by atomic layer deposition on WBG semiconductors (silicon carbide and gallium nitride), as either amorphous or crystalline films. The impacts of deposition modes and pre- or postdeposition treatments are both discussed. Moreover, the dielectric behaviour of these films is also presented, and some examples of high-κ binary oxides applied to SiC and GaN transistors are reported. The potential advantages and the current limitations of these technologies are highlighted. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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15 pages, 3686 KB

Open AccessArticle

Phase Properties of Different HfO₂ Polymorphs: A DFT-Based Study

by Emiliano Laudadio, Pierluigi Stipa, Luca Pierantoni and Davide Mencarelli

Crystals 2022, 12(1), 90; https://doi.org/10.3390/cryst12010090 - 10 Jan 2022

Cited by 33 | Viewed by 12298

Abstract

Background: Hafnium Dioxide (HfO₂) represents a hopeful material for gate dielectric thin films in the field of semiconductor integrated circuits. For HfO_2, several crystal structures are possible, with different properties which can be difficult to describe in detail from an experimental point of view. In this study, a detailed computational approach has been shown to present a complete analysis of four HfO₂ polymorphs, outlining the intrinsic properties of each phase on the basis of atomistic displacements. Methods: Density functional theory (DFT) based methods have been used to accurately describe the chemical physical properties of the polymorphs. Corrective Hubbard (U) semi-empirical terms have been added to exchange correlation energy in order to better reproduce the excited-state properties of HfO₂ polymorphs. Results: the monoclinic phase resulted in the lowest cohesive energy, while the orthorhombic showed peculiar properties due to its intrinsic ferroelectric behavior. DFT + U methods showed the different responses of the four polymorphs to an applied field, and the orthorhombic phase was the least likely to undergo point defects as oxygen vacancies. Conclusions: The obtained results give a deeper insight into the differences in excited states phenomena in relation to each specific HfO₂ polymorph. Full article

(This article belongs to the Special Issue Advanced Semiconductor Materials and Devices)

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12 pages, 14762 KB

Open AccessArticle

Comparison of Hafnium Dioxide and Zirconium Dioxide Grown by Plasma-Enhanced Atomic Layer Deposition for the Application of Electronic Materials

by Zhigang Xiao, Kim Kisslinger, Sam Chance and Samuel Banks

Crystals 2020, 10(2), 136; https://doi.org/10.3390/cryst10020136 - 23 Feb 2020

Cited by 30 | Viewed by 9875

Abstract

We report the growth of nanoscale hafnium dioxide (HfO₂) and zirconium dioxide (ZrO₂) thin films using remote plasma-enhanced atomic layer deposition (PE-ALD), and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using the HfO₂ and ZrO₂ thin films as the gate oxide. Tetrakis (dimethylamino) hafnium (Hf[N(CH₃)₂]₄) and tetrakis (dimethylamino) zirconium (IV) (Zr[N(CH₃)₂]₄) were used as the precursors, while O₂ gas was used as the reactive gas. The PE-ALD-grown HfO₂ and ZrO₂ thin films were analyzed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The XPS measurements show that the ZrO₂ film has the atomic concentrations of 34% Zr, 2% C, and 64% O while the HfO₂ film has the atomic concentrations of 29% Hf, 11% C, and 60% O. The HRTEM and XRD measurements show both HfO₂ and ZrO₂ films have polycrystalline structures. n-channel and p-channel metal-oxide semiconductor field-effect transistors (nFETs and pFETs), CMOS inverters, and CMOS ring oscillators were fabricated to test the quality of the HfO₂ and ZrO₂ thin films as the gate oxide. Current-voltage (IV) curves, transfer characteristics, and oscillation waveforms were measured from the fabricated transistors, inverters, and oscillators, respectively. The experimental results measured from the HfO₂ and ZrO₂ thin films were compared. Full article

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19 pages, 6779 KB

Open AccessArticle

Characterization of HfO₂ Optical Coatings Deposited by MF Magnetron Sputtering

by Artur Wiatrowski, Agata Obstarczyk, Michał Mazur, Danuta Kaczmarek and Damian Wojcieszak

Coatings 2019, 9(2), 106; https://doi.org/10.3390/coatings9020106 - 8 Feb 2019

Cited by 59 | Viewed by 8479

Abstract

The aim of this work is to determine the influence of medium frequency magnetron sputtering powers on the various properties of hafnium dioxide (HfO₂) thin films. Microstructure observations show that an increase in the sputtering power has a significant influence on HfO₂ films’ microstructure. As-deposited hafnia thin films exhibit nanocrystalline structure with a monoclinic phase, however the rise of the sputtering power results in an increase of crystallite sizes. Atomic force microscopy investigations show that the surface of the deposited films is smooth, crack-free, and composed of visible grains. The surface roughness and the value of the water contact angle increase with the increase of the sputtering power. Measurements of the optical properties show that HfO₂ coatings are transparent in the visible wavelength range. A higher sputtering power causes a decrease of an average transmittance level and a simultaneous increase of the real part of the refractive index. Nanoindentation measurements reveal that the thin film hardness and Young’s elastic modulus increase with an increase in the sputtering power. Moreover, the results of plasticity index H/E and plastic resistance parameter H³/E² are discussed. Based on the obtained results, a correlation between the sputtering power and the structural, surface, and optical properties, as well as the hardness and Young’s elastic modulus, were determined. Full article

(This article belongs to the Special Issue Thin Film Deposition and Characterization Techniques)

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