Les biocapteurs ont pour objectif de détecter de faible quantité de biomolécules afin d'améliorer laqualité et la précocité des diagnostics médicaux. Parmi eux, les transistors à nanofils sont desdispositifs prometteurs, car ils permettent la détection électrique de biomolécules sans marquage avecune grande sensibilité et un temps de réponse court. Actuellement, la plupart de ces dispositifs utilisedes nanofils de silicium, qui peuvent être limités par une faible résistance chimique, ce qui entrainedes variations du signal en présence de solutions biologiques. Pour palier ces inconvénients, le carburede silicium (SiC) est un matériau prometteur déjà utilisé dans le domaine biomédical pour lafabrication ou le recouvrement de prothèses ou de vis médicales. Outre ses propriétés semiconductrices,ce matériau est biocompatible et montre une forte inertie chimique. Par conséquent, ilouvre une voie à l'intégration in-vivo des capteurs.L'objectif de cette thèse est d'élaborer des biocapteurs SiC à l'échelle nanométrique pour détecter desmolécules d'ADN. La première étape est la fabrication des transistors à base de nanofils SiC à grillearrière. Un procédé original de fonctionnalisation combiné avec la lithographie et aboutissant augreffage covalent de molécules sondes d'ADN a été mis au point. Finalement, la réponse des capteursa été mesurée entre chaque étape du protocole de fonctionnalisation. Les variations du signal lors desétapes de greffage et d'hybridation des molécules d'ADN démontrent la capacité de ces dispositifs àdétecter des molécules d'ADN. Des mesures complémentaires ont aussi montré la stabilité, lasélectivité et la réversibilité du dispositif. / Biosensors are designed to detect small quantities of biomolecules in order to improve the accuracyand earliness of medical diagnosis. Among them, nanowire transistors are promising devices, as theyallow the electrical detection of biomolecules without labeling with high sensitivity and a shortresponse time. Currently, most of these devices use silicon nanowires, which can be limited by a lowchemical resistance, which leads to signal variations in the presence of biological solutions. Toovercome these limitations, silicon carbide (SiC) is a promising material already used in thebiomedical field for the coating of prosthesis or bone screws. In addition to its semiconductingproperties, this material is biocompatible and shows a high chemical inertness. Therefore, it opens theway for in vivo integration of sensors.The goal of this thesis is to develop SiC biosensors at the nanoscale to detect DNA molecules. Thefirst step is the fabrication of SiC nanowire-based back gate transistors. A novel process combiningfunctionalization and lithography leading to the covalent grafting of DNA probe molecules has beendeveloped. Finally, the sensor response was measured between each step of the functionalizationprocess. The variations of the signal during the steps of grafting and hybridization of DNA moleculesdemonstrate the ability of these devices to detect DNA molecules. Additional steps have also shownthe stability, selectivity and reversibility of the device.

<div>Germanium-based MOS device which is considered as one of the promising alternative channel materials has been studied with well-known FinFET, nanowire structures and HKMG (High-k metal gate). Recent introduction of Ferroelectric (FE) Zr-doped HfO₂ (Hf_xZr_1-xO₂, HZO) has opened various possibilities both in memory and logic</div><div>applications.</div><div><br></div><div>First, integration of FE HZO into the conventional Ge platform was studied to demonstrate Ge FeFET. The FE oxide was deposited with optimized atomic layer deposition (ALD) recipe by intermixing HfO₂ and ZrO₂. The HZO film was characterized with FE tester, XRD and AR-XPS. Then, it was integrated into conventional gate stack of Ge devices to demonstrate Ge FeFETs. Polarization switching was measured with ultrafast measurement set-up down to 100 ps.</div><div><br></div><div>Then, HZO layer was controlled for the first demonstration of hysteresis-free Ge negative capacitance (NC) CMOS FinFETs with sub-60mV/dec SS bi-directionally at room temperature towards possible logic applications. Short channel effect in Ge NCFETs were compared with our reported work to show superior robustness. For smaller widths that cannot be directly written by the e-beam lithography tool, digital etching on Ge fins were optimized.</div><div>Lastly, Ge FeFET-based synaptic device for neuromorphic computing was demonstrated. Optimum pulsing schemes were tested for both potentiation and depression which resulted in highly linear and symmetric conductance profiles. Simulation was done to analyze Ge FeFET's role as a synaptic device for deep neural network.</div>

Rapid and reliable diagnostics of a disease represents one of the main focuses of today’s academic and industrial research in the development of new sensor prototypes and improvement of existing technologies. With respect to demographic changes and inhomogeneous distribution of the clinical facilities worldwide, especially in rural regions, a new generation of miniaturized biosensors is highly demanded offering an easy deliverability, low costs and sample preparation and simple usage. This work focuses on the integration of nanosized electronic structures for high-specific sensing applications into adequate microfluidic structures for sample delivery and liquid manipulation. Based on the conjunction of these two technologies, two novel sensor platforms were prototyped, both allowing label-free and optics-less electrochemical detection ranging from molecular species to eukaryotic micron-sized human cells.:Table of Figures List of Tables Abbreviations List of Symbols 1 Introduction 1.1 Motivation 1.2 State of the art 1.3 Scope of this thesis 2 Fundamentals 2.1 Sensors at the nanoscale 2.2 Transistors technology 2.2.1 p-n junction 2.2.3 The MOSFET 2.2.4 The ISFET and BioFET 2.3 Impedance measurements for biodetection 2.3.1 Electrical impedance spectroscopy 2.3.2 Electrical impedance cytometry 2.4 Microfluidics 2.4.1 Definition 2.4.2 Droplet-based microfluidics 2.5 Biomarkers for sensing applications 2.5.1 Peripheral blood mononuclear cells (PBMCs) 2.5.2 Physical parameters 3. Material and methods 3.1 General 3.1.1 Materials and chemicals 3.1.2 Surface cleaning 3.2 Lithography 3.2.1 Electron beam lithography 3.2.2 Laser lithography 3.2.3 UV lithography 3.2.4 Soft lithography 3.3 Thermal deposition of metals 3.4 APTES functionalization 3.4.1 Fluorescent labeling of APTES 3.5 Measurement devices 3.5.1 SiNW FET measurements 3.5.2 Electrical Impedance cytometry measurements 3.6 Bacteria and cell cultivation 3.6.1 PBMC purification and treatment 3.6.2 Bacteria cultivation 4. Compact nanosensors probe microdroplets 4.1 Overview 4.2 Fabrication 4.2.1 SiNW FET fabrication 4.2.2 SiNW FET modification for top-gate sensing 4.3 Electrical characterization 4.4 Flow-focusing droplet generation 4.4.1 Flow-focusing geometry 4.4.2 Flow-focusing droplet characterization 4.4.3 Microfluidic integration 4.5 Deionized water droplet sensing 4.6 Phosphate-buffered saline (PBS) droplet sensing 4.6.1 Influence of the droplet’s ionic concentration 4.6.2 Plateau formation in dependence of the droplet’s settling time 4.6.3 Droplet analysis by their ratio 4.6.4 Dependence on pH value 4.6.5 Long time pH sensing experiment 4.6.6 Dependence on ionic concentration 4.7 Tracking of reaction kinetics in droplets 4.7.1 Principle and setup of the glucose oxidase (GOx) enzymatic test 4.7.2 GOx enzymatic assay 4.8 Stable baseline by conductive carrier phase 5. Impedance-based flow cytometer on a chip 5.1 Overview 5.2 Overview of the fabrication of the sensor device 5.3 COMSOL simulation of sensing area 5.3.1 Prototyping of the sensing geometry 5.3.2 Optimization of the sensing geometry 5.3.3 Evaluation of the working potential 5.3.4. Scaling of the sensing area 5.4 Fabrication of the nanoelectronic sensing structure 5.4.1 Nanofabrication and analysis 5.4.2 Evaluation of the proximity effect 5.5 Microcontacting of nanostructured sensing structures 5.6 Electrical characterization of the sensing structure 5.6.1 Characterization in alternating current 5.6.2 Characterization in direct current (DC) 5.7 Scaling effect of nanostructures in static sensing conditions 5.8 Multi-analyte detection on the sensor 5.9 Microfluidic focusing system 5.9.1 1D focusing using FITC-probed deionized water 5.9.2 2D Focusing using fluorescent microparticles 5.10 Microfluidic integration of the two technologies 5.11 Dynamic SiO2 particle detection 5.11.1 Single particle detection 5.11.2 Scatter plot representation 5.11.3 Effect of the sensing area in dynamic particle detection 5.11.4 Dynamic detection of SiO2 particles with different diameters 5.12 Detection of peripheral blood mononuclear cells (PBMCs) 5.12.1 Overview 5.12.2 PBMC classification detected by impedance cytometry 5.12.3 PBMC Long-time detection 5.13 Detection of acute myeloid leukemia by impedance cytometry 5.13.1 Manual analysis of the output response 5.13.2 Learning algorithm for automatic cell classification 5.14 Exploring the detection limit of the device 6. Summary and outlook Scientific output References Acknowledgements / Rasche und zuverlässige biologische Krankheitsdiagnostik repräsentiert eines der Hauptfokusse heutiger akademischer und industrieller Forschung in der Entwicklung neuer Sensor-Prototypen und Verbesserung existierender Technologien. In bezug auf weltweite demographische Änderungen und hohe Distanzen zu Kliniken, besonders in ländlichen Gegenden, werden zusätzliche Anfordungen an neue miniaturisierte Biosensor-Generationen gestellt, wie zum Beispiel ihre Transportfähigkeit, geringe Kosten und Probenpräparation, sowie einfache Handhabung. Diese Dissertation beschäftigt sich mit der Integration nanoskalierter Strukturen zur Detektion chemischer und biologischer Spezies und mikrofluidischen Kanälen zu deren Transport und zur Manipulation der Ströme. Basierend auf der Verbindung dieser beiden Technologien wurden zwei Sensor-Plattformen entwickelt, die eine markierungsfreie und nicht-optische elektrische Detektion von Molekülen bis zu eukaryotischen menschlichen Zellen erlauben.:Table of Figures List of Tables Abbreviations List of Symbols 1 Introduction 1.1 Motivation 1.2 State of the art 1.3 Scope of this thesis 2 Fundamentals 2.1 Sensors at the nanoscale 2.2 Transistors technology 2.2.1 p-n junction 2.2.3 The MOSFET 2.2.4 The ISFET and BioFET 2.3 Impedance measurements for biodetection 2.3.1 Electrical impedance spectroscopy 2.3.2 Electrical impedance cytometry 2.4 Microfluidics 2.4.1 Definition 2.4.2 Droplet-based microfluidics 2.5 Biomarkers for sensing applications 2.5.1 Peripheral blood mononuclear cells (PBMCs) 2.5.2 Physical parameters 3. Material and methods 3.1 General 3.1.1 Materials and chemicals 3.1.2 Surface cleaning 3.2 Lithography 3.2.1 Electron beam lithography 3.2.2 Laser lithography 3.2.3 UV lithography 3.2.4 Soft lithography 3.3 Thermal deposition of metals 3.4 APTES functionalization 3.4.1 Fluorescent labeling of APTES 3.5 Measurement devices 3.5.1 SiNW FET measurements 3.5.2 Electrical Impedance cytometry measurements 3.6 Bacteria and cell cultivation 3.6.1 PBMC purification and treatment 3.6.2 Bacteria cultivation 4. Compact nanosensors probe microdroplets 4.1 Overview 4.2 Fabrication 4.2.1 SiNW FET fabrication 4.2.2 SiNW FET modification for top-gate sensing 4.3 Electrical characterization 4.4 Flow-focusing droplet generation 4.4.1 Flow-focusing geometry 4.4.2 Flow-focusing droplet characterization 4.4.3 Microfluidic integration 4.5 Deionized water droplet sensing 4.6 Phosphate-buffered saline (PBS) droplet sensing 4.6.1 Influence of the droplet’s ionic concentration 4.6.2 Plateau formation in dependence of the droplet’s settling time 4.6.3 Droplet analysis by their ratio 4.6.4 Dependence on pH value 4.6.5 Long time pH sensing experiment 4.6.6 Dependence on ionic concentration 4.7 Tracking of reaction kinetics in droplets 4.7.1 Principle and setup of the glucose oxidase (GOx) enzymatic test 4.7.2 GOx enzymatic assay 4.8 Stable baseline by conductive carrier phase 5. Impedance-based flow cytometer on a chip 5.1 Overview 5.2 Overview of the fabrication of the sensor device 5.3 COMSOL simulation of sensing area 5.3.1 Prototyping of the sensing geometry 5.3.2 Optimization of the sensing geometry 5.3.3 Evaluation of the working potential 5.3.4. Scaling of the sensing area 5.4 Fabrication of the nanoelectronic sensing structure 5.4.1 Nanofabrication and analysis 5.4.2 Evaluation of the proximity effect 5.5 Microcontacting of nanostructured sensing structures 5.6 Electrical characterization of the sensing structure 5.6.1 Characterization in alternating current 5.6.2 Characterization in direct current (DC) 5.7 Scaling effect of nanostructures in static sensing conditions 5.8 Multi-analyte detection on the sensor 5.9 Microfluidic focusing system 5.9.1 1D focusing using FITC-probed deionized water 5.9.2 2D Focusing using fluorescent microparticles 5.10 Microfluidic integration of the two technologies 5.11 Dynamic SiO2 particle detection 5.11.1 Single particle detection 5.11.2 Scatter plot representation 5.11.3 Effect of the sensing area in dynamic particle detection 5.11.4 Dynamic detection of SiO2 particles with different diameters 5.12 Detection of peripheral blood mononuclear cells (PBMCs) 5.12.1 Overview 5.12.2 PBMC classification detected by impedance cytometry 5.12.3 PBMC Long-time detection 5.13 Detection of acute myeloid leukemia by impedance cytometry 5.13.1 Manual analysis of the output response 5.13.2 Learning algorithm for automatic cell classification 5.14 Exploring the detection limit of the device 6. Summary and outlook Scientific output References Acknowledgements

There is a compelling need to explore different material options as well as device structures to facilitate smooth transistor scaling for higher speed, higher density and lower power. The enormous potential of nanoelectronics, and nanotechnology in general, offers us the possibility of designing devices with added functionality. However, at the same time, the new materials come with their own challenges that need to be overcome. In this work, we have addressed some of these challenges in the context of quasi-2D Silicon, III-V semiconductor and graphene. Bulk Si is the most widely used semiconductor with an indirect bandgap of about 1.1 eV. However, when Si is thinned down to sub-10nm regime, the quasi-2D nature of the system changes the electronic properties of the material significantly due to the strong geometrical confinement. Using a tight-binding study, we show that in addition to the increase in bandgap due to quantization, it is possible to transform the original in direct bandgap to a direct one. The effective masses at different valleys are also shown to vary uniquely in an anisotropic way. This ultra-thin Si, when used as a channel in a double gate MOSFET structure, creates so called “volume in version” which is extensively investigated in this work. It has been found that the both the quantum confinement as well as the gating effect play a significant role in determining the spatial distribution of the charge, which in turn has an important role in the characteristics of transistor. Compound III-V semiconductors, like Inx Ga1-xAs, provide low effective mass and low density of states. This, when coupled with strong confinement in a nanowire channel transistor, leads to the “Ultimate Quantum Capacitance Limit” (UQCL) regime of operation, where only the lowest subband is occupied. In this regime, the channel capacitance is much smaller than the oxide capacitance and hence dominates in the total gate capacitance. It is found that the gate capacitance change qualitatively in the UQCL regime, allowing multi-peak, non-monotonic capacitance-voltage characteristics. It is also shown that in an ideal condition, UQCL provides improved current saturation, on-off ratio and energy-delay product, but a degraded intrinsic gate delay. UQCL shows better immunity towards series resistance effect due to increased channel resistance, but is more prone to interfacial traps. A careful design can provide a better on-off ratio at a given gate delay in UQCL compared to conventional MOSFET scenario. To achieve the full advantages of both FinFET and HEMT in III-V domain, a hybrid structure, called “HFinFET” is proposed which provides excellent on performance like HEMT with good gate control like FinFET. During on state, the carriers in the channel are provided using a delta-doped layer(like HEMT) from the top of a fin-like non-planar channel, and during off state, the gates along the side of the fin(like FinFET) help to pull-off the carriers from the channel. Using an effective mass based coupled Poisson-Schrodinger simulation, the proposed structure is found to outperform the state of the art planar and non-planar MOSFETs. By careful optimization of the gate to source-drain underlap, it is shown that the design window of the device can be increased to meet ITRS projections at similar gate length. In addition, the performance degradation of HFinFET in presence of interface traps has been found to be significantly mitigated by tuning the underlap parameter. Graphene is a popular 2D hexagonal carbon crystal with extraordinary electronic, mechani-cal and chemical properties. However, the zero band gap of grapheme has limited its application in digital electronics. One could create a bandgap in grapheme by making quasi-1D strips, called nanoribbon. However, the bandgap of these nanoribbons depends on the the type of the edge, depending on which, one can obtain either semiconducting or metallic nanoribbon. It has been shown that by the application of an external transverse field along the sides of a nanoribbon, one could not only modulate the magnitude of the bandgap, but also change it from direct to indirect. This could open up interesting possibilities for novel electronic and optoelectronic applications. The asymmetric potential distribution inside the nanoribbon is found to result in such direct to indirect bandgap transition. The corresponding carrier masses are also found to be modulated by the external field, following a transition from a“slow”electron to a“fast” electron and vice-versa. Experimentally, it is difficult to control the bandgap in nanoribbons as precise edge control at nanometer scale is nontrivial. One could also open a bandgap in a bilayer graphene, by the application of vertical electric field, which has raised a lot of interest for digital applications. Using a self-consistent tight binding theory, it is found that, inspite of this bandgap opening, the intrinsic bias dependent electronic structure and the screening effect limit the subthreshold slope of a metal source drain bilayer grapheme transistor at a relatively higher value-much above the Boltzmann limit. This in turn reduces the on-off ratio of the transistor significantly. To overcome this poor on-off ratio problem, a semiconductor source-drain structure has been proposed, where the minority carrier injection from the drain is largely switched off due to the bandgap of the drain. Using a self-consistent Non-Equilibrium Green’s Function(NEGF) approach, the proposed device is found to be extremely promising providing unipolar grapheme devices with large on-off ratio, improved subthreshold slope and better current saturation. At high drain bias, the transport properties of grapheme is extremely intriguing with a number of nontrivial effects. Optical phonons in monolayer grapheme couple with carriers in a much stronger way as compared to a bilayer due to selection rules. However, it is difficult to experimentally probe this through transport measurements in substrate supported grapheme as the surface polar phonons with typical low activation energy dominates the total scattering. However, at large drain field, the carriers obtain sufficient energy to interact with the optical phonons, and create so called ‘hot phonons’ which we have experimentally found to result in a negative differential conductance(NDC). The magnitude of this NDC is found to be much stronger in monolayer than in bilayer, which agrees with theoretical calculations. This NDC has also been shown to be compensated by extra minority carrier injection from drain at large bias resulting in an excellent current saturation through a fundamentally different mechanism as compared to velocity saturation. A transport model has been proposed based on the theory, and the experimental observations are found to be in agreement with the model.