Flash Memory Devices

Flash memory devices have represented a breakthrough in storage since their inception in the mid-1980s, and innovation is still ongoing. The peculiarity of such technology is an inherent flexibility in terms of performance and integration density according to the architecture devised for integration. The NOR Flash technology is still the workhorse of many code storage applications in the embedded world, ranging from microcontrollers for automotive environment to IoT smart devices. Their usage is also forecasted to be fundamental in emerging AI edge scenario. On the contrary, when massive data storage is required, NAND Flash memories are necessary to have in a system. You can find NAND Flash in USB sticks, cards, but most of all in Solid-State Drives (SSDs). Since SSDs are extremely demanding in terms of storage capacity, they fueled a new wave of innovation, namely the 3D architecture. Today “3D” means that multiple layers of memory cells are manufactured within the same piece of silicon, easily reaching a terabit capacity. So far, Flash architectures have always been based on "floating gate," where the information is stored by injecting electrons in a piece of polysilicon surrounded by oxide. On the contrary, emerging concepts are based on "charge trap" cells. In summary, flash memory devices represent the largest landscape of storage devices, and we expect more advancements in the coming years. This will require a lot of innovation in process technology, materials, circuit design, flash management algorithms, Error Correction Code and, finally, system co-design for new applications such as AI and security enforcement

Memristors

This Edited Volume Memristors - Circuits and Applications of Memristor Devices is a collection of reviewed and relevant research chapters, offering a comprehensive overview of recent developments in the field of Engineering. The book comprises single chapters authored by various researchers and edited by an expert active in the physical sciences, engineering, and technology research areas. All chapters are complete in itself but united under a common research study topic. This publication aims at providing a thorough overview of the latest research efforts by international authors on physical sciences, engineering, and technology,and open new possible research paths for further novel developments

Fast Transients in Non-Volatile Resistive Memories (RRAM) Using Tantalum Pentoxide as Solid Electrolyte

The semiconductor electronics industry has followed Moore\u27s law austerely since 1965 fueling the microelectronics revolution and major technological advancements. Over the recent decades, the semiconductor industry has proven to be very successful, particularly by scaling the geometry of devices ever smaller. The device scaling has been very effective in boosting productivity yielding astonishing integration levels while simultaneously dramatically dropping the price per bit. However, the future of device scaling remains unclear. It is certain that device scaling will face severe reliability, cost and energy issues in the future. Therefore, there is a need to identify alternative technology platforms. Reconfigurable devices are considered as one of the key alternatives. However, the widespread aggressive acceptance of reconfigurable devices in the semiconductor industry faces many different challenges. One of the major challenges is the size of the switching matrix. One solution to overcome this challenge is to replace the present SRAM (Static Random Access Memory) switch with a non-volatile resistive memory switch. Some of the advantages of these switches are low cost, CMOS compatibility and simple structure. Given such advantages, it is essential to elucidate the working principle as well as the reliability issues. Since these non-volatile resistive switch devices are new to the semiconductor electronics industry, it is crucially important to explore novel structures for improved device architectures and to develop adequate measurement techniques to inspect and characterize these novel resistive switch devices. In this thesis, novel structures of RRAM devices with constricted electrode area close to the size of a single conducting filament of around 10 nm have been explored to improve device performance. Also, new measurement setups have been developed and proprietary test circuits have been designed, built and tested in order to acquire accurate and reliable data to investigate device performance. Some of the notable achievements of the developed measurement setups are measurement capability of switching transient with accuracy of 4 ns, high resistance measurements up to 1.6 GΩ, accurate endurance test within 1 ms/cycle and limiting current during SET to \u3c 20 μA without noticeable overshoot within 500 ps

Etude d'architectures et d'empilements innovants de mémoires Split-Gate (grille séparée) à couche de piégeage discret

Du fait de l'augmentation de la demande de produits pour les applications grand public, industrielles et automobiles, des mémoires embarquées fiables et à faible coût de fabrication sont de plus en plus demandées. Dans ce contexte, les mémoires split-gate à piégeage discret sont proposées pour des microcontrôleurs. Elles combinent l'avantage d'une couche de stockage discrète et de la con guration split-gate. Durant ce travail de recherche, des mémoires split-gate à couche de piégeage discret ayant des longueurs de grille de 20nm sont présentées pour la première fois. Celles-ci on été réalisées avec des nanocristaux de silicium (Si-nc), du nitrure de silicium (SiN) ou un hybride Si-nc/SiN avec diélectrique de control de type SiO2 ou AlO et sont comparées en termes de performances lors des procédures d'eff acement et de rétention. Ensuite, la miniaturisation des mémoires split-gate à piégeage de charge est étudié, en particulier au travers de l'impact de la réduction de la longueur de grille sur la fenêtre de mémorisation, la rétention et la consommation. Le rôle des défauts dans le diélectrique de contrôle (alumine) utilisé dans les mémoires de type TANOS a été étudié. Des travaux ont été menés pour déterminer l'origine des pièges dans ce matériau, par le biais de la simulation atomistique ainsi que d'analyses physico-chimiques précises. Nous avons montré que la concentration de pièges dans AlO pouvait être réduite par ajustement des conditions de procédé de fabrication, débouchant ainsi sur l'amélioration de la rétention dans les mémoires à piégeage de charge. Ce résultat est convenable pour les applications de type embarquéDue to the increasing demand for consumer, industrial and automotive products, highly reliable, and low integration cost embedded memories are more and more required. In this context, split-gate charge trap memories were proposed for microcontroller products, combining the advantage of a discrete storage layer and of the split-gate con guration. In this thesis, split-gate charge trap memories with electrical gate length down to 20nm are presented for the 1st time. Silicon nanocristals (Si-nc), or silicon nitride (SiN) and hybrid Si-nc/SiN based split-gate memories, with SiO2 or AlO control dielectrics, are compared in terms of program erase and retention. Then, the scalability of split-gate charge trap memories is studied, investigating the impact of gate length reduction on the memory window, retention and consumption. We thus studied the role of defects on alumina control dielectric employed in TANOS-like memory. We used atomistic simulation, consolidated by a detailed alumina physico-chemical material analysis, to investigate the origin of traps in alumina. We showed that the trap concentration in AlO can be decreased by adjusting the process conditions leading to improved retention behaviour in charge trap memory, suitable for embedded applications.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

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

Optimization of performance and reliability of HZO-based capacitors for ferroelectric memory applications

In an era in which the amount of produced and stored data continues to exponentially grow, standard memory concepts start showing size, power consumption and costs limitation which make the search for alternative device concepts essential. Within a context where new technologies such as DRAM, magnetic RAM, resistive RAM, phase change memories and eFlash are explored and optimized, ferroelectric memory devices like FeRAM seem to showcase a whole range of properties which could satisfy market needs, offering the possibility of creating a non-volatile RAM. In fact, hafnia and zirconia-based ferroelectric materials opened up a new scenario in the memory technology scene, overcoming the dimension scaling limitations and the integration difficulties presented by their predecessors perovskite ferroelectrics. In particular, HfₓZr₁₋ₓO₂ stands out because of high processing flexibility and ease of integration in the standard semiconductor industry process flows for CMOS fabrication. Nonetheless, further understanding is necessary in order tocorrelate device performance and reliability to the establishment of ferroelectricity itself. The aim of this work is to investigate how the composition of the ferroelectric oxide, together with the one of the electrode materials influence the behavior of a ferroelectric RAM. With this goal, different process parameters and reliability properties are considered and an analysis of the polarization reversal is performed. Starting from undoped hafnia and zirconia and subsequently examining their intermixed system, it is shown how surface/volume energy contributions, mechanical stress and oxygen-related defects all concur in the formation of the ferroelectric phase. Based on the process optimization of an HfₓZr₁₋ₓO₂-based capacitor performed within these pages, a 64 kbit 1T1C FeRAM array is demonstrated by Sony Semiconductor Solutions Corporation which shows write voltage and latency as low as 2.0 V and 16 ns, respectively. Outstanding retention and endurance performances are also predicted, which make the addressed device an extremely strong competitor in the semiconductor scene

The impact of perfectionism on well-being: Shame in perfectionism’s influence on emotion regulation

The aim of the present study was to understand the role of shame as it relates to distinguishing adaptive from maladaptive perfectionism in the ability to modulate emotions effectively. A sample of 200 participants ages 18 and older completed online self-report measures related to perfectionism, emotion regulation, and self-conscious affects, along with a stressful task, the PASAT-C. Results showed that shame can explain the relationship between perfectionistic concerns (often labeled as maladaptive perfectionism) and both effective and ineffective emotion regulation strategies. They also showed that shame can explain the relationship between perfectionistic strivings (often labeled as adaptive perfectionism) and ineffective emotion regulation strategies. These findings contradict the idea that perfectionism can be neatly divided into a maladaptive and adaptive binary. The results suggest that while shame is a negative affective experience and can have negative consequences, it may have positive consequences in certain forms and intensity levels once it crosses a certain threshold of intensity. Acknowledging one’s feelings of shame may also contribute to shame’s utility in promoting effective emotion regulation strategies in perfectionists. Limitations of the study, along with future directions are discussed in order to deepen understanding related to the concepts of perfectionism, shame and emotion regulation