Effect of eco-friendly solvents in solution-based ZrOx dielectrics

Over the past decade, solution-based dielectric oxides have been widely studied in electronic applications, enabling the use of low-cost processing technologies and device improvement. Among many high-к dielectrics, zirconium oxide (ZrOx) has been regarded as one of the most promising inorganic dielectric materials for its excellent properties. This work aims to study the effect of environmentally friendly solvents, in order to replace the conventional ones and obtain a safer working environment and optimize solution-based ZrOx. dielectrics. For this, ZrOx thin films were produced with different solvents and different process conditions by sol-gel method. Its microstructure and electronic properties as dielectrics in thin films metal-insulator-semiconductor structured capacitors for high-frequency circuits were investigated systematically. It was found that the capacitors obtained from a zirconium nitrate-based precursor solution with a concentration of 0.2 M in 2-methoxyethanol (2-ME) annealed at 300 °C showed an average dielectric constant of 8.7 ± 0.6 and a low leakage current density of (2.2 ± 2.7) × 10-8 A/cm2 at 1 MV/cm. However, 2-ME is a toxic solvent that can cause serious harm to human health as such eco-friendly solvents were tested. Ethanol-based ZrOx capacitors were successfully produced at 300 °C showing an average dielectric constant of 10.8 ± 0.2 and a leakage current density of (8.7 ± 0.4) × 10-7 A/cm2 at 1 MV/cm. Looking towards the future of electronics, metal-insulator-metal capacitors were processed on a flexible substrate at a low temperature of 150 °C combined with deep ultra-violet (DUV) irradiation, showing an average dielectric constant 11 ± 1 and a low leakage current density of (4.7 ± 4.7) × 10-7 A/cm2 at 0.5 MV/cm. Finally, the optimized ZrOx dielectric thin films were successfully applied as gate insulator in solution-processed In2O3 TFTs

Nano-structural, Electrical and Mechanical Characterization of Zirconium Oxide Thin Films as a Function of Annealing Temperature and Time

Zr thin films were deposited by DC magnetron sputtering technique on Si substrate and then post-annealed at different temperatures (150-750 °C in steps of 150 °C) and times (60 and 180 min) with flow of oxygen. X-ray diffraction (XRD) method was used for study of crystallographic structure. These results showed an orthorhombic structure for annealed films at 150 and a mixed structure of monoclinic and tetragonal for annealed films at higher temperatures (300-750 ºC). XRD result also showed that an increase in annealing temperature and time caused increasing of crystalline size. EDAX and AFM tech-niques were employed for investigation of chemical composition and surface morphology of samples, re-spectively. The results showed a granular structure for all samples, while the O / Zr ratio, grains size and surface roughness were increased with increasing of annealing temperature and time. A two probe instru-ment was used for electrical properties investigation, while hardness of films was measured by nano-indentation test. These results showed that increasing of annealing temperature and time caused increas-ing of electrical resistance and decreasing of hardness in the films. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3513

Nanoscale Oxidation of Zirconium Surfaces: Kinetics and Mechanisms

We show that atomic force microscope-induced oxide features can be formed reproducibly on both Zr and ZrN surfaces, and that the growth rate decreases rapidly with increasing time. There is an increase in oxide-feature height with humidity for both systems, and an approximately linear dependence of the height of the structures on the applied voltage for all films for short exposure times. As the anodization time increases, only the thinnest (6 nm) films show a large enhancement in oxide-feature height, demonstrating the role of the film/substrate interface. Under the same conditions, the height of features grown on ZrN films is greater than for those grown on Zr films, indicating that nitrogen plays a role in the oxidation process. (C) 2003 American Vacuum Society

Recent Advances in Metal, Ceramic, and Metal-Ceramic Composite Films/Coatings

This reprint gathers works on various coating materials and technologies aimed at the improvement of materials’ properties, such as corrosion resistance or biocompatibility. Systematic studies demonstrate how the structure and morphology of coatings can change the mechanical, chemical and various functional properties of materials. The reprint contributes to the better understanding of various phenomena induced by metal, ceramic or composite coatings in core materials and, thus, it can help in the more rational design of the selected material’s properties in future studies by the application of coatings

Material development of doped hafnium oxide for non-volatile ferroelectric memory application

Seit der Entdeckung von Ferroelektrizität in Hafniumoxid stellt es aufgrund seiner Prozesskompatibilität im Bereich der Mikroelektronik sowie seiner besonderen Eigenschaften ein wachsendes Forschungsfeld dar. Im Speziellen wird die Anwendung in nicht-flüchtigen Speichern, in neuromorphen Bauelementen sowie in piezo-/pyroelektrischen Sensoren untersucht. Jedoch ist das Verhalten von ferroelektrischem Hafniumoxid im Vergleich zu Ferroelektrika mit Perovskit-Struktur nicht im Detail verstanden. Zudem spielen Prozesseinflüsse während und nach der Abscheidung eine entscheidende Rolle für die Materialeigenschaften aufgrund der metastabilen Natur der ferroektrischen Phase in diesem Materialsystem. In dieser Arbeit werden die grundlegenden physikalischen Eigenschaften von Hafniumoxid, Prozesseinflüsse auf die Mikrostruktur und Zuverlässigkeitsaspekte von nicht-flüchtigen sowie neuromorphen Bauelementen untersucht. Im Bezug auf die physikalischen Eigenschaften zeigen sich hier deutliche Belege für ferroelastische 90° Domänenwandbewegungen in Hafniumoxid-basierten Dünnschichten, welche in einem ähnlichen Verhalten wie ein Antiferroelektrikum resultieren. Weiterhin wird über die Entdeckung von einer mittels elektrischem Feld induzierten Kristallisation in diesem Materialsystem berichtet. Für die Charakterisierung der Mikrostruktur wird als neue Methode Transmissions-Kikuchi-Diffraktion eingeführt, welche eine detaillierte Untersuchung der lokalen kristallographischen Phase, Orientierung und Gefügestruktur ermöglicht. Hierbei zeigen sich deutliche Vorzugsorientierungen in Abhängigkeit des Substrates, der Dotierstoffkonzentration sowie der Glühtemperatur. Auf Basis dieser Ergebnisse lassen sich die beobachteten Zuverlässigkeitsverhalten in Bauelementen erklären und mittels Defektkontrolle weiter optimieren. Schließlich wird das Verhalten in neuromorphen Bauelementen untersucht und Leitlinien für Prozess- und Bauelementoptimierung gegeben.:Abstract i Abstract ii List of Figures vi List of Tables x Acronyms xi Symbols xiv 1 Introduction 1 2 Theoretical background 3 2.1 Behavior of ferroelectric materials 3 2.1.1 Phase transitions at the Curie temperature 4 2.1.2 Domains, domain walls, and microstructure 5 2.2 Ferroelectricity in HfO2 6 2.2.1 Thermodynamics and kinetics 8 2.2.2 Antiferroelectric-like behavior, wake-up effect, and fatigue 11 2.2.3 Piezo- and pyroelectric effects 13 2.3 Ferroelectric FETs 13 2.3.1 Endurance, retention and variability 14 2.3.2 Neuromorphic devices 15 3 Methodology 17 3.1 Electrical analysis 17 3.1.1 Capacitors 17 3.1.2 FeFETs 19 3.2 Structural and chemical analysis 20 3.2.1 Grazing-incident X-ray diffraction (GIXRD) 20 3.2.2 Transmission electron microscopy (TEM) 20 3.2.3 Time-of-flight secondary ion mass spectrometry (ToF-SIMS) 21 3.3 Transmission Kikuchi diffraction 21 3.4 Sample preparation 23 4 The physics of ferroelectric HfO2 25 4.1 Ferroelastic switching 25 4.2 Electric field-induced crystallization 30 5 Microstructure engineering 33 5.1 Microstructure and ferroelectric domains in HfO2 33 5.2 Doping influences 34 5.2.1 Zr doping (similar ionic radius) 35 5.2.2 Si doping (smaller ionic radius) 43 5.2.3 La doping (larger ionic radius) 50 5.2.4 Co-doping 50 5.3 Annealing influences 53 5.4 Interlayer influences 58 5.5 Interface layer influences 62 5.5.1 Structural differences in the HfO2 layer 63 5.5.2 Interactions of the interface and HfO2 layer 67 5.5.3 Substrate-driven changes in the Si-doping profile 73 5.6 Phenomenological wake-up behaviors and process guidelines 77 6 HfO2-based ferroelectric FETs 81 6.1 Endurance, retention and variability 81 6.1.1 Analytic model of HfO2-based FeFETs 84 6.1.2 Endurance improvements by interface fluorination 94 6.2 Neuromorphic devices and circuits 98 6.2.1 Current peroclation paths in FeFETs 100 6.2.2 Material and stack influences on synaptic devices 105 6.2.3 Reliability aspects of synaptic devices 106 7 Conclusion and outlook 109 Appendix 142 Density-functional-theory calculations 142 Supplementary Figures 143 Publications 145 Acknowledgment 156 Declaration 158The discovery of ferroelectricity in hafnium oxide spurred a growing research field due to hafnium oxides compatibility with processes in microelectronics as well as its unique properties. Notably, its application in non-volatile memories, neuromorphic devices as well as piezo- and pyroelectric sensors is investigated. However, the behavior of ferroelectric hafnium oxide is not understood into depth compared to common perovskite structure ferroelectrics. Due the the metastable nature of the ferroelectric phase, process conditions have a strong influence during and after its deposition. In this work, the physical properties of hafnium oxide, process influences on the microstructure as well as reliability aspects in non-volatile and neuromorphic devices are investigated. With respect to the physical properties, strong evidence is provided that the antiferroelectric-like behavior in hafnium oxide based thin films is governed by ferroelastic 90° domain wall movement. Furthermore, the discovery of an electric field-induced crystallization process in this material system is reported. For the analysis of the microstructure, the novel method of transmission Kikuchi diffraction is introduced, allowing an investigation of the local crystallographic phase, orientation and grain structure. Here, strong crystallographic textures are observed in dependence of the substrate, doping concentration and annealing temperature. Based on these results, the observed reliability behavior in the electronic devices is explainable and engineering of the present defect landscape enables further optimization. Finally, the behavior in neuromorphic devices is explored as well as process and design guidelines for the desired behavior are provided.:Abstract i Abstract ii List of Figures vi List of Tables x Acronyms xi Symbols xiv 1 Introduction 1 2 Theoretical background 3 2.1 Behavior of ferroelectric materials 3 2.1.1 Phase transitions at the Curie temperature 4 2.1.2 Domains, domain walls, and microstructure 5 2.2 Ferroelectricity in HfO2 6 2.2.1 Thermodynamics and kinetics 8 2.2.2 Antiferroelectric-like behavior, wake-up effect, and fatigue 11 2.2.3 Piezo- and pyroelectric effects 13 2.3 Ferroelectric FETs 13 2.3.1 Endurance, retention and variability 14 2.3.2 Neuromorphic devices 15 3 Methodology 17 3.1 Electrical analysis 17 3.1.1 Capacitors 17 3.1.2 FeFETs 19 3.2 Structural and chemical analysis 20 3.2.1 Grazing-incident X-ray diffraction (GIXRD) 20 3.2.2 Transmission electron microscopy (TEM) 20 3.2.3 Time-of-flight secondary ion mass spectrometry (ToF-SIMS) 21 3.3 Transmission Kikuchi diffraction 21 3.4 Sample preparation 23 4 The physics of ferroelectric HfO2 25 4.1 Ferroelastic switching 25 4.2 Electric field-induced crystallization 30 5 Microstructure engineering 33 5.1 Microstructure and ferroelectric domains in HfO2 33 5.2 Doping influences 34 5.2.1 Zr doping (similar ionic radius) 35 5.2.2 Si doping (smaller ionic radius) 43 5.2.3 La doping (larger ionic radius) 50 5.2.4 Co-doping 50 5.3 Annealing influences 53 5.4 Interlayer influences 58 5.5 Interface layer influences 62 5.5.1 Structural differences in the HfO2 layer 63 5.5.2 Interactions of the interface and HfO2 layer 67 5.5.3 Substrate-driven changes in the Si-doping profile 73 5.6 Phenomenological wake-up behaviors and process guidelines 77 6 HfO2-based ferroelectric FETs 81 6.1 Endurance, retention and variability 81 6.1.1 Analytic model of HfO2-based FeFETs 84 6.1.2 Endurance improvements by interface fluorination 94 6.2 Neuromorphic devices and circuits 98 6.2.1 Current peroclation paths in FeFETs 100 6.2.2 Material and stack influences on synaptic devices 105 6.2.3 Reliability aspects of synaptic devices 106 7 Conclusion and outlook 109 Appendix 142 Density-functional-theory calculations 142 Supplementary Figures 143 Publications 145 Acknowledgment 156 Declaration 15

Aatomkihtsadestatud tsirkooniumipõhiste nanolaminaatide ja segukilede magnetilised, elektrilised ja struktuursed omadused

Väitekirja elektrooniline versioon ei sisalda publikatsiooneDoktoritöös kasutati aatomkihtsadestamise meetodit, eesmärgiga valmistada multiferroidne nanoskaalas kile, ehk paarikümne nanomeetri paksune materjalikiht. Multiferroid on selline materjal, mis on üheaegselt nii ferromagnetiline kui ka ferroelektriline, st polariseerub nii välises magnet- kui ka elektriväljas ning on võimeline mõlemat polarisatsiooni säilitama ka välise välja eemaldamisel. Sellist materjali oleks võimalik kasutada uue põlvkonna nanoelektroonikas, näiteks mäluseadmete valmistamiseks. Aatomkihtsadestamise meetod valiti, kuna see on ennast tõestanud, kui üks sobivamaid viise üliõhukeste tahkiskihtide valmistamiseks ühtlase paksuse ja koostisega üle suure pinna. Kirjandusallikate põhjal oli teada, et materjali valmistamine, mis oleks üheaegselt nii ferromagnetiline kui ka ferroelektriline, ei ole lihtne ülesanne. Nimetatud nähtusi on tuvastatud ühe materjali samas faasis ainult ülimadalatel temperatuuridel ja/või suurtes materjalitükkides. Autorile teadaolevalt ei ole multiferroidi suudetud valmistada õhukese materjalikihina ning toimivana ka toatemperatuuril või kõrgemal. Mõlemad nimetatud tingimused on kindlasti tarvilikud, et rääkida võimalikest praktilistest rakendustest. Erinevates ZrO2 sisaldavates kiledes demonstreeriti osa kilede puhul ferromagnetilist hüstereesi ning osa käitus elektriväljas ferroelektrikule sarnaselt. Ühel juhul tuvastati ferromagnetiline ja ferroelektriline polariseeritavus samas kilenäidises. Järeldati, et kuigi traditsioonilisest ferromagnetismist rääkimiseks ei ole nanoskaalas metalloksiidkilede puhul põhjust, siis teatud juhtudel võivad siiski defektid, nagu näiteks hapnikuvakantsid, materjali ferromagnetilist käitumist põhjustada. Kuigi defektid raskendavad ferroelektrilise polarisatsiooni mõõtmist, võib leida nö. tasakaalupunkti piisava hulga defektide vahel, et saavutada ferromagnetiline polarisatsioon ja piisavalt vähese hulga defektide vahel, et ferroelektriline efekt ei jää veel täielikult piirpindadel tekkiva lekkevoolust tingitud polarisatsiooni varju. Autori arvates tuvastati selline olukord, kui defektirohke ferromagnetiline ZrO2 segati vähem defektse materjaliga HfO2, mille puhul võis kirjandusele toetudes oodata ferroelektrilisust.The main goal was to fabricate a multiferroic nanoscale film using atomic layer deposition. Multiferroic is a material that is both ferromagnetic and ferroelectric, that is, polarizes in both magnetic and electric fields, and retains that polarization after removing the external field. Such a material could be used in novel nanoelectronics applications, such as memory devices or sensors. Atomic layer deposition was chosen to fabricate the films, because this is the method actually used in modern nanoelectronics to deposit ultrathin films, and the only method which can provide conformal films over a large substrate area and at the same time provide thickness control at the nanometer level. It was known beforehand, from literature, that a material possessing ferromagnetic and ferroelectric behavior in the same sample in the same phase will be a difficult task. This phenomenon has been observed in bulk materials and/or very low temperatures, but not in thin films and at room temperature, which are both necessary, if one wishes to consider an actual nanoelectronics application. In various ZrO2-based thin films, it was shown that some films showed ferromagnetic hysteresis and some exhibited behavior resembling ferroelectric response. In one case, ferromagnetic and ferroelectric behavior were observed in the same material sample. It was concluded that although one cannot speak of ferromagnetism in the traditional sense, when thin metal oxide films are studied, but in certain cases, ferromagnetism may still arise from the defects of a material, such as oxygen vacancies. Although these defects make the detection of ferroelectricity harder, a reasonable trade-off can be found between enough defects to induce ferromagnetism and not so much to overwhelm the signs of ferroelectricity completely. The author believes such as case was found, when a defective material, which was found ferromagnetic in all cases, namely ZrO2, was mixed with a less defective material, HfO2, known already in literature to be ferroelectric in some cases.https://www.ester.ee/record=b536107

The pervasive presence of oxygen in ZrC

Based on the recent interest in oxy-carbide materials in catalysis, we employ a thin film model concept to highlight that variation of key reaction parameters in the reactive magnetron sputtering of zirconium carbide films (sputtering power, template temperature or reactive plasma environment) under realistic preparation and application conditions often results in zirconium oxy-carbide films of varying stoichiometry. The composition of the films grown on silicon wafers and in vacuo - cleaved NaCl (001) single crystal facets was confirmed by depth profiling X-ray photoelectron spectroscopy and electron microscopy analysis. A correlation between methane-to-argon ratio, excess carbon and template temperature with elemental composition emphasizes the exclusive presence of oxygen-containing zirconium carbides. To generalize the approach, we also show that embedding of highly ordered Cu particles with uniform sizes in zirconium oxy-carbide matrices yields well-defined metal / oxy-carbide interfaces. As the presence of an oxy-carbide and its reactivity has been inextricably linked to enhanced activity and selectivity in a variety of processes, including hydrogenation, oxidation or reduction reactions, our model thin film approach provides the necessary well-defined catalysts to derive mechanistic details and to study the decomposition/re-carburization cycles of oxy-carbides. We have exemplified the concept for zirconium oxy-carbide, but deliberate extension to similar systems is easily possible