THERMAL DEPENDENCE OF LOW-FREQUENCY NOISE IN POLYSILICON THIN FILM TRANSISTORS

International audienceThermal dependence of low frequency noise in low temperature (600°C) polysilicon thin film transistors is studied in devices biased from weak to moderate inversion and operating in the linear mode. Drain current noise spectral density, measured in the temperature range from 260K to 310K, is thermally activated following the Meyer Neldel rule. Analysis of the thermal activation of noise, supported by the theory of trapping/detrapping processes of carriers into oxide traps located close to the interface, leads to the calculation of the deep state interface distribution in function of the Meyer Neldel characteristic energy

Discussion on the figures of merit of identified traps located in the Si film : surface versus volume trap densities

The aim of this work is a discussion on the figures of merit of identified traps located in the depletion zone (Si film) of advanced MOSFET devices. Two methodologies to estimate the volume trap densities are investigated, one using the relationship between the surface trap density and volume trap density and a second one based on the temperature evolution at fixed frequency of the generation-recombination plateau level associated to the same trap. By comparing the volume trap densities estimated using these two methods, the results are not agreeing with each other, suggesting that these methods can no longer be used with accuracy in multigate devices. Moreover, they may lead in certain cases to results physically not correct. Even about of the volume defects, the linear evolution between the plateau and the characteristic frequency of the generation-recombination contributions associated to the same trap give us the surface trap density without any additional assumption

Numerical Simulation of Low-Frequency Noise in Polysilicon Thin-Film Transistors

3 pagesInternational audienceNumerical simulations of low-frequency noise are carried out in two technologies of N-channel polysilicon thin-film transistors (TFTs) biased from weak to strong inversion and operating in the linear mode. Noise is simulated by generation/recombination processes. The contribution of grain boundaries on the noise level is higher in the strong inversion region. The microscopic noise parameter that is deduced from numerical simulations is lower than the macroscopic one defined according to the Hooge empirical relationship and deduced from noise measurements. The higher macroscopic value is attributed to the drain-current crowding induced by nonconducting spots in the devices due to structural defects. The ratio of these two noise parameters can be considered as an indicator to qualify TFT technology

Numerical simulation of conduction and low-frequency noise in polysilicon thin film transistors

4 pagesInternational audienceNumerical simulations of static conduction and low-frequency noise are carried out in N-channel polysilicon thin film transistors. The Meyer-Neldel effect associated with the drain current is related to trapping/detrapping processes of carriers from dangling bonds located at the interface. Low-frequency noise is simulated by generation-recombination processes. The sources responsible of noise in the thin film transistors are mainly located close to the interface. The microscopic parameter deduced from numerical simulation is lower than the macroscopic one deduced from noise measurements. The ratio of these two parameters is considered as a factor of merit to qualify thin film transistor technology

Poststroke Spasticity: Pathophysiology and Management An Accurate Evaluation of Spasticity

Stroke is a major contributor to long-term impairment and disability, affecting up to one-third of survivors and almost half of patients showing neurological deficit at six months. Spasticity affects approximately 25% of individuals within two weeks of a stroke and increases to 44% in patients who have had a second stroke. Severe or incapacitating spasticity affects 15% of post-stroke individuals. Poststroke spasticity is also linked to additional signs and symptoms of the upper motor neuron syndrome, such as simultaneous contraction of agonist and antagonist muscles, weakness of the muscles, and a lack of coordination. Spasticity arises due to aberrant neuroplasticity that develops after a stroke and there is currently no specific intervention method designed to address and correct this abnormal plasticity that takes place during the acute phase. Just before implementing any measures to deal with spasticity, it is crucial to evaluate the influence on the quality of life and level of severity. Several grading scales are used to measure spasticity such as the MAS and modified Tardieu scale.There are various therapeutic approaches that may be categorized into three main classes: physical, pharmaceutical, and surgical. Each class has a distinct purpose and is used at the appropriate moment to reduce the level of spasticity and improve the patient's health. Physiotherapy serves as a base of improving the patient's condition and facilitating the development of brain networks. The objective of post stroke spasticity management must include not only the reduction of muscle hypertonia, but also the evaluation of how post stroke influences functionality and overall mental health. Improper treatment or non-compliance may result in increased pain, joint contraction, and further disability. The goal is to assist the patient in achieving the best possible quality of life

LIGHTNING IMPULSE MODELING AND SIMULATION OF DRY-TYPE AND OIL-IMMERSED POWER- AND DISTRIBUTION TRANSFORMERS

This paper presents in detail numerical methods and techniques for lightning impulse (LI) modeling and simulation of power and distribution transformers. The modeling methods are based on equivalent circuits of transformer winding entities resulting from the initial winding discretization determined by the required accuracy. The parameters of the equivalent circuit such as resistances and self- and mutual capacitances and inductances are obtained from field simulations (FEM). The circuit equations of the transformer’s equivalent circuit written in the state space form yield a large system of differential equations that is solved in time-domain by using the standard Runge-Kutta numerical integration technique. The obtained solution represents the voltage distribution over the winding in each moment of the LI-time (50μs). The results verification by comparison against measurements is presented in detail

Bruit électrique basse fréquence comme outil de diagnostic non destructif pour des technologies MOS submicroniques et nanométriques

Ce mémoire représente une synthèse des travaux de recherche effectués lors des dix dernières années sur l'étude du bruit basse fréquence dans des transistors MOS fortement submicroniques et nanométriques. L'étude du bruit intrinsèque dans les transistors MOS s'avère d'une importance fondamentale car les fluctuations du courant (tension) traversant le canal sont induites par des pièges situés à l'interface canal / diélectrique de grille, dans la profondeur de l'oxyde de grille ou dans la zone de déplétion du transistor ; ces pièges peuvent apparaitre pendant les différentes étapes technologiques de fabrication des transistors ou être liées à la qualité des matériaux utilisés ; les études du bruit permettent ainsi d'évaluer la qualité et la fiabilité des composants et également de comprendre certains phénomènes physiques liés au transport des porteurs qui peuvent être observés dans le fonctionnement du transistor MOS. Les résultats présentés sont originaux car les transistors étudiés sont réalisés en utilisant des procédés intégrant les principales innovations technologiques de ces dernières années ; mais aussi car les études ont été portées sur une large gamme de températures (10 K et de 77 K à 300 K). En plus de l'identification des pièges dans la zone de déplétion des transistors par la méthode de spectroscopie du bruit, ces études du bruit en fonction de la température ont permis de valider plusieurs hypothèses et de mettre en évidence des mécanismes qui n'auraient pas pu être observés si les études avait été effectuées uniquement à température ambiante. Les études montrent que l'étude du bruit basse fréquence s'avère un outil de diagnostic non destructif de caractérisation électrique très fructueux pour avoir une meilleure compréhension des mécanismes de transport de charge régnant dans le canal d'inversion des transistors ; et fournissant un facteur de mérite permettant d'évaluer la fiabilité et d'accompagner la miniaturisation des transistors dans les technologies ultimes

The Model of the Philosopher in The Hieroglyphic History: the Cynical Wolf

Being aware of the fact that the wolf had a negative reputation, Dimitrie Cantemir chose to negotiate the symbolic tradition in order to highlight some traits that could be turned into positive features. So, he abandoned some sources and used only that ones which he could interpret as he liked to. The character is, in spite of the examples that insist upon his fierceness, the wisest among the other animals and a real scholar, being an adept of the cynical philosophical trend. Yet, he betrays sometimes the characteristics of this philosophy. In The Hieroglyphic History, the Wolf is a symbol of Reason.Bestiary, Wolf, Philosopher, cynic, disobedience of tradition

Performances et fiabilité des transistors MOS SUB-0.1[mu]m

L'objet de notre travail est relatif à une analyse prospective de l'évolution de la fiabilité et des effets de canal court compte tenu de l'avancée des technologies induite par la miniaturisation, particulièrement pour des transistors MOS de longueur de grille inférieure à 0.1æm. Nous présentons une approche simple des équations qui modélisent le fonctionnement du transistor MOS et nous introduisons les effets liés à la réduction des dimensions. Les effets de canaux court ont été étudiés en fonction de la température. Une méthode originale d'extraction des paramètres qui prend en compte le deuxième facteur d'atténuation de la mobilité et une nouvelle méthode dite "ratio" pour l'extraction de la longueur effective du canal et de la tension de seuil sont proposées. Les effets des porteurs chauds ont été également analysés en fonction de la température. Les mécanismes et les modèles d'ionisation par impact sont présentés afin de mieux comprendre les processus de génération des porteurs chauds. La dégradation induite par injection de porteurs chauds a été mise en évidence pour chaque technologie disponible. A cet égard, l'impact du type de contrainte électrique et de l'architecture technologique sur la fiabilité des composants a été étudié. Une méthode originale d'évaluation de la contribution du canal et des extensions source-drain sur la dégradation totale est présentée. La durée de vie des dispositifs a été extrapolée afin de déterminer une tension de drain maximale pour laquelle les composants peuvent fonctionner durant une période raisonnablement longue.GRENOBLE1-BU Sciences (384212103) / SudocGRENOBLE INP-Phelma (381852301) / SudocSudocFranceF