Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

X-Ray Diffraction

The move to implement metal oxide based gate dielectrics in a metal-oxide-semiconductor field effect transistor is considered one of the most dramatic advances in materials science since the invention of silicon based transistors. Metal oxides are superior to SiO 2 in terms of their higher dielectric constants that enable the required continuous down-scaling of the electrical thickness of the dielectric layer while providing a physically thicker layer to suppress the quantum mechanical tunneling through the dielectric layer. Over the last decade, hafnium based materials have emerged as the designated dielectrics for future generation of nano-electronics with a gate length less than 45 nm, though there exists no consensus on the exact composition of these materials, as evolving device architectures dictate different considerations when optimizing a gate dielectric material. In addition, the implementation of a non-silicon based gate dielectric means a paradigm shift from diffusion based thermal processes to atomic layer deposition processes. In this report, we review how HfO 2 emerges from all likely candidates to become the new gold standard in the microelectronics industry, its different phases, reported electrical properties, and materials processing techniques. Then we use specific examples to discuss the evolution in designing hafnium based materials, from binary to complex oxides and to non-oxide forms as gate dielectric, metal gates and diffusion barriers. To address the impact of these hafnium based materials, their interfaces with silicon as well as a variety of semiconductors are discussed. Finally, the integration issues are highlighted, including carrier scattering, interface state passivation, phonon engineering, and nano-scale patterning, which are essential to realize future generations of devices using hafnium-based high- k materials.

Development of hafnium based high-k materials—A review

The unexpected ferroelectric properties of nanoscale hafnia-zirconia are considered to be promising for a wealth of applications including ferroelectric memory, field effect transistors, and energy-related applications. However, the reason why the unexpected ferroelectric Pca21 phase can be stabilized has not been clearly understood although numerous extensive theoretical and experimental results have been reported recently. The ferroelectric orthorhombic phase is not a stable phase under processing conditions from the viewpoint of bulk free energy. Although the possibility of stabilization of the ferroelectric phase due to the surface energy effect has been theoretically suggested, such a theoretical model has not been systematically compared with actual experimental results. In this study, the experimental observations on polymorphism in nanoscale HfO2–ZrO2 solid solution thin films of a wide range of film compositions and thicknesses are comprehensively related to the theoretical predictions based on a thermodynamic surface energy model. The theoretical model can semi-quantitatively explain the experimental results on the phase-evolution, but there were non-negligible discrepancies between the two results. To understand these discrepancies, various factors such as the film stress, the role of a TiN capping layer, and the kinetics of crystallization are systematically studied. This work also reports on the evolution of electrical properties of the film, i.e. dielectric, ferroelectric, anti-ferroelectric, and morphotropic phase changes, as a function of the film composition and thickness. The in-depth analyses of the phase change are expected to provide an important guideline for subsequent studies.

Surface and grain boundary energy as the key enabler of ferroelectricity in nanoscale hafnia-zirconia: a comparison of model and experiment

https://ir.nctu.edu.tw/bitstream/11536/21381/1/000316677900001.pdf

Growth, dielectric properties, and memory device applications of ZrO2 thin films

We review and critique the recent developments on multifunctional oxide materials, which are gaining a good deal of interest. Recongnizing that this is a vast area, the focus of this treatment is mainly on high-κ dielectric, ferroelectric, magnetic, and multiferroic materials. Also, we consider ferrimagnetic oxides in the context of the new, rapidly developing field of negative-index metamaterials. This review is motivated by the recent resurgence of interest in complex oxides owing to their coupling of electrical, magnetic, thermal, mechanical, and optical properties, which make them suitable for a wide variety of applications, including heat, motion, electric, and magnetic sensors; tunable and compact microwave passive components; surface acoustic wave devices; nonlinear optics; and nonvolatile memory, and pave the way for designing multifunctional devices and unique applications in spintronics and negative refraction-index media. For most of the materials treated here, structural and physical propertie...

Oxides, Oxides, and More Oxides: High-κ Oxides, Ferroelectrics, Ferromagnetics, and Multiferroics

https://web.yonsei.ac.kr/semicim/Publications/Paper/Int/18.Char.process.zro2.mombe.pdf

Characteristics and processing effects of ZrO2 thin films grown by metal-organic molecular beam epitaxy

HfO2 dielectric layers were grown on the p-type Si(1 0 0) substrate by metal-organic molecular beam epitaxy (MOMBE). Hafnium-tetrabutoxide [Hf(O·t-C4H9)4] was used as a Hf precursor and argon gas was used as a carrier gas. The microstructure and thickness of HfO2 films were measured by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The electrical characteristics of the HfO2 layers were evaluated by high frequency (HF) capacitance–voltage (C–V) and current–voltage (I–V) measurements. The surface morphology, crystal structure, and chemical binding states of HfO2 films were also examined by atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) measurements. HF C–V and I–V measurements have shown that HfO2 layer grown by MOMBE has higher dielectric constant (k) of 20–22 and lower leakage current density of ∼10 −8 A/cm 2 compared with the conventional SiO2. In addition, it has been shown that the HfO2 layer has fixed oxide charge of about 8 × 10 11 cm −2 and interfacial state density of about 1 × 10 12 eV −1 cm −2 . The electrical characteristics and surface morphology of HfO2 films are affected by O 2/Ar gas flow ratio. Finally, post-metallization annealing (PMA) was carried out to reduce the interface state density. © 2005 Elsevier B.V. All rights reserved.

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Characterization and process effects of HfO2 thin films grown by metal-organic molecular beam epitaxy

Growth and characterization of MOMBE grown HfO2

https://web.yonsei.ac.kr/semicim/Publications/Paper/Int/29.Modeling_growth_rate.pdf

Myoung Seok Kim

Papers

Characteristics and processing effects of ZrO2 thin films grown by metal-organic molecular beam epitaxy

Characterization and process effects of HfO2 thin films grown by metal-organic molecular beam epitaxy

Growth and characterization of MOMBE grown HfO2

Modeling growth rate of HfO2 thin films grown by metal–organic molecular beam epitaxy