Ce travail de thèse présente la conception d’un convertisseur Buck 3 états pour améliorer le comportement dynamique des tensions d’alimentations des microprocesseurs. La topologie du convertisseur est dans un premier temps, implémentée en technologie IBM CMOS 180 nm pour la validation de la structure 3 états. Le prototype réalisé utilise une tension d’entrée de 3.6V et génère une tension de sortie de 0.8V à 2V. Sa réponse aux transitoires de charge ne montre que 1 à 2% de surtension prouvant ainsi l’avantage du régulateur en dynamique. Le convertisseur 3 états est dans un deuxième temps intégré en technologie 28 nm CMOS HPM (cette technologie est essentiellement utilisée pour les microprocesseurs). Les résultats des tests effectués sur le prototype réalisé confirment les performances en économie d’énergie, de surface et de réponse dynamique. Ce prototype délivre en effet 0.5 à 1.2V en sortie pour 1.8V en entrée et présente un rendement maximal de 90%. Les mesures de régulation dynamique montrent qu’il permet d’obtenir moins de 5% de bruit sur le processeur et 10 mV/ns de commutation de tensio / This thesis work consists into the design of a 3 states buck converter targeting the improvement of dynamic regulation of microprocessors supplies. The topology of the converter is, at first, implemented in IBMCMOS 180 nm technology to validate the transient performances of the3 states regulator. The prototype in 180 nm, uses an input voltage of 3.6V and outputs a voltage in the range of 0.8V to 2V. Its response to load transients shows about 1% of undershoot and 2 % of overshoot, proving a good dynamic behavior for a simple structure compared to state of the art.The 3 states converter is then integrated in 28 nm CMOS HPM (technologymostly used for microprocessors desgn). The experimental results on the prototype confirm the performances in terms of energy and area savings, aswell as dynamic response. The chip delivers 0.5V to 1.2V from a 1.8V supply,and shows a 90% peak efficiency. The measurements of dynamic regulation show less than 5% of noise on the processor supply and 10 mV/ns outputvoltage switching for DVFS purpose.

This master´s thesis describes switch mode power supply. The aim of this master´s thesis is the design and the construction of the switch mode power supply, which will be used as a laboratory tool.

Avec l'hétérogénéité des réseaux et la demande croissante de services multimédias, la Qualité d'Expérience (QoE) devient un facteur déterminant de réussite ou d’échec de ces services. Dans cette thèse, nous avons d’abord analysé l'impact des paramètres de qualité sur l'engagement de l'utilisateur, afin de comprendre l’effet des paramètres vidéo (temps de démarrage, qualité intrinsèque, taux de blocage) et la popularité du service sur l'engagement de l'utilisateur. Nos résultats ont montré que le taux de blocage et la popularité du service sont des paramètres critiques qui impactent fortement la satisfaction et l'engagement de l’utilisateur, tandis que, le temps de démarrage a moins d’impact. Ensuite, les approches subjectives de QoE comme le Mean Opinion Score (MOS) ont été traité dans cette thèse, où les utilisateurs sont appelés à donner une note de satisfaction en fonction des informations de contextes. Une analyse statistique des résultats obtenus à partir de tests utilisateurs a montré que le type de terminal et de contenu sont des paramètres qui impactent fortement le MOS. En plus, des modèles mathématiques d’estimation de QoE en fonction des informations de contextes ont été proposés. Enfin, deux techniques d’optimisations ont été proposées : Le MDASH (MOS Dynamic Adaptive Streaming over HTTP) pour l’optimisation vidéo de flux partageant les mêmes ressources, de manière à garantir une certaine QoE pour tous les utilisateurs. Et une optimisation de livraison, basée sur des fonctions d’utilités dans laquelle, une fonction globale d'utilité est calculée en fonction de différentes contraintes (qui dépendent fortement des stratégies des acteurs de la chaîne de livraison) / With the network heterogeneity and increasing demand of multimedia services, Quality of Experience (QoE) becomes a crucial determinant of the success or failure of these services. In this thesis, we first propose to analyze the impact of quality metrics on user engagement, in order to understand the effects of video metrics (video startup time, average bitrate, buffering ratio) and content popularity on user engagement. Our results show that video buffering and content popularity are critical parameters which strongly impacts the end-user’s satisfaction and user engagement, while the video startup time appears as less significant. On other hand, we consider subjective approaches such as the Mean Opinion Score (MOS) for evaluating QoE, in which users are required to give their assessment according to contextual information. A detailed statistical analysis of our study shows the existence of non-trivial parameters impacting MOS (the type of device and the content type). We propose mathematical models to develop functional relationships between the QoE and the context information which in turn permits us to estimate the QoE. A video content optimization technique called MDASH (for MOS Dynamic Adaptive Streaming over HTTP) is proposed, which improves the perceived QoE for different video sessions sharing the same local network, while taking QoE fairness among users as a leitmotiv. We also propose a utility-based approach for video delivery optimization, in which a global utility function is computed based on different constraints (e.g. target strategies coming from the actors of the delivery chain)

[ES] Encontrar un método no invasivo de clasificación fiable para distinguir entre pacientes con cancer de próstata e hiperplasia benigna de próstata no es una tarea trivial. El antígeno prostático específico mas utilizado presenta un au- mento en otras situaciones como la retención de orina o la eyaculación. Los productos metabólicos celulares como los compuestos volatiles en forma de bio-fluidos presentan una oportunidad para estudiarlos con la tecnología de semiconductores de óxido de metal. Una nariz electrónica diseñada para estos biofiuidos podría convertirse en una prueba ambulatoria clave para disminuir el número de biopsias. El diseño 3D, la creación de circuitos electrónicos, neumáticos, la adecuación de las muestras, la creación de una base de datos estandarizada para narices electrónicas, la definición de una interfaz de usuario amigable para el profesional sanitario, un sistema securizado para la comunicación con un servidor de almacenamiento de datos y todo el software necesario para hacer viable la democratización de las narices electrónicas en atención hospitalaria configuran la estrategia del trabajo. Además, el método empleado para conseguir aumentar el número de datos ha resultado determinante para hacer mas sencillo el entrenamiento de la red neuronal con la que se ha logrado una precisión del 87% en la clasificación entre pacientes de cancer de próstata e hiperplasia benigna de próstata. Se ha escogido un formato libro donde recoger todos los aspectos significativos de la realización del estudio. El primer capítulo se centra en el proyecto de tesis a financiar, la problemática a resolver, los objetivos y el plan de trabajo. En el segundo capítulo se definen los conceptos, el sentido del olfato, la vejiga, la próstata, los sensores utilizados, indicadores de cancer y otros elementos como la nariz electrónica. Es con una nariz electrónica de donde se obtienen las señales que se tratan en el capítulo tercero. En este capítulo se muestran las características de las señales provenientes de pacientes con cancer de próstata y pacientes con hiperplasia benigna de próstata, su tratamiento, filtrado, comparación y uso para la clasificación de pacientes. Asimismo, se muestran dos métodos distintos de clasificación y estudio de los algoritmos para automatizar la misma. El capítulo cuarto se centra en la construcción de un prototipo. Se ha abordado este capítulo como un manual de construcción que permita al lector conocer el proceso realizado, la toma de decisiones y la técnica utilizada para la realización del hardware, software y el modelo 3D. Dado que la diversidad de especialidades que confluyen en el mismo proyecto puede imposibilitar el dominio de alguno de los campos tratados, incluso dentro del mismo campo de especialización, se ha preparado este capítulo con diagramas y código fu- ente que acompaña a las explicaciones de forma detallada. El propósito de este capítulo es permitir a investigadores de diversas areas de conocimiento su construcción sin necesidad de profundizar en otros campos. Además, en este capítulo se detallan los procedimientos a fin de favorecer la democratización de la nariz electrónica como instrumento científico y con la esperanza de proporcionar la base para futuras implementaciones en la comunidad científica. Para el autor, la tesis no es sólo un documento, es un período de evolución personal. Ha estado condicionada por factores diversos, una pandemia, el planteamiento inicial, la financiación, el grupo de acogida, la línea de investigación, el desarrollo socio-económico del autor y el propio autoaprendizaje en el proceso de ejecución. Es por ello que se ha plasmado en el capítulo quinto lo que ha guiado de una u otra manera, pero de forma significativa, la toma de decisiones. Este capítulo versa sobre el trabajo futuro y tres proyectos, COST y H2020, DE1-SoC ADC e-Nose y Detección de tumores, que han ejercido influencia en el desarrollo de la tesis. Las conclusiones se recogen en el capítulo sexto. No obstante, cada capítulo dispone de un apartado llamado "Reflexiones" donde se anotan aquellas ideas y conclusiones concretas sobre el mismo. De esta forma se proporciona al lector un instrumento de lectura rápida que permita su consulta como si se tratara de un manual, sin necesidad de leer la totalidad del documento. En resumen, en este estudio se detallan los métodos y procedimientos de la investigación realizada con pacientes de cáncer de próstata e hiperplasia benigna de próstata con el propósito de conseguir un prototipo de una nariz electrónica para la clasificación de pacientes haciendo uso de orina como biofluido. Se ha tratado de escribir una referencia desde la que seguir construyendo conocimiento en torno a las narices electrónicas aplicadas a la clasificación de pacientes. / [CA] Trobar una mètode no invasiu de classificació fiable per a distingir entre pacients amb càncer de pròstata i hiperplàsia benigna de pròstata no és una tasca trivial. L'antigen prostàtic específic més utilitzat presenta un augment en altres situacions com la retenció d'orina o l'ejaculació. Els productes metabòlics cel·lulars com els compostos volàtils en forma de bio-fluids presenten una oportunitat per tal d'estudiar-los amb la tecnologia de semiconductors d'òxid de metall. Un nas electrònic dissenyat per a aquestos bio-fluids podria convertir-se en una prova ambulatòria clau per tal de disminuir el nombre de biòpsies. El disseny 3D, la creació de circuits electrònics, pneumàtics, l'adequació de les mostres, la creació d'una base de dades estandarditzada per a nassos electrònics, la definició d'una interfície d'usuari amigable per al professional sanitari, un sistema securitzat per a la comunicació amb un servidor d'emmagatzemament de dades i tot el software necessari per tal de fer viable la democratització dels nassos electrònics en atenció hospitalària configuren l'estratègia del treball. A més, el mètode emprat per a aconseguir augmentar el nombre de dades ha resultat determinant per fer més senzill l'entrenament de la xarxa neuronal amb la qual s'ha aconseguit una precisió del 87% a la classificació entre pacients de càncer de pròstata i hiperplàsia benigna de pròstata. S'ha escollit un format llibre on recollir tots els indrets significatius de la realització de l'estudi. El primer capítol es centra en el projecte de tesi a finançar, la problemàtica a resoldre, els objectius i el pla de treball. Al segon capítol es defineixen els conceptes, el sentit de l'olfacte, la bufeta, la próstata, els sensors utilitzats, indicadors de càncer i altres elements com el nas electrònic. És amb un nas electrònic d'on s'obtenen les senyals que es tracten al capítol tercer. En aquest capítol es mostren les característiques dels senyals provinents de pacients amb càncer de pròstata i pacients amb hiperplàsia benigna de próstata, el seu tractament, filtrat, comparació i ús per a la classificació de pacients. Així mateix, es mostren dos mètodes diferents de classificació i estudi dels algorismes per a automatitzar la mateixa. El capítol quart es centra en la construcció d'un prototip. S'ha abordat aquest capítol com un manual de construcció que permeta al lector conéixer el procés realitzat, la presa de decisions i la tècnica emprada pera la realització tant del hardware, els software i com el model 3D. Com que la diversitat d'especialitats que conflueixen en el mateix projecte pot impossibilitar el domini d'algun dels camps tractats, inclòs dins del mateix camp d'especialització, s'ha preparat aquest capítol amb diagrames i codi font que acompanya les explicacions de forma detallada. El propòsit d'aquest capítol és permetre a investigadors de diverses àrees de coneixement la seva construcció sense necessitat d'aprofundir en altres camps. A més, en aquest capítol es detallen els procediments per tal d'afavorir la democratització del nas electrònic com a instrument científic i amb la esperança de proporcionar la base per a futures implementacions en la comunitat científica. Per a l'autor, la tesi no és sols un document, és un període d'evolució personal. Ha estat condicionada per factors diversos, una pandèmia, el plantejament inicial, el finançament, el grup d'acollida, la línia d'investigació, el desenvolupament socio-econòmic de l'autor i el propi autoaprenentatge al procés d'execució. És per això que s'ha plasmat al capítol cinqué allò que ha guiat d'una manera o d'altra, però de forma significativa, la presa de decisions. Aquest capítol versa sobre el treball futur i tres projectes, COST i H2020, DE1-SoC ADC e-Nose i Detecció de tumors, que han exercit influència al desenvolupament de la tesi. És un exercici de reflexió al voltant dels mateixos i són una mostra de la capacitat investigadora de l'autor. Les conclusions es recullen al capítol sisé. No obstant això, cada capítol disposa d'un apartat anomenat "Reflexions" on s'anoten aquelles idees i conclusions concretes sobre el mateix. D'aquesta manera es proporciona al lector un instrument de lectura ràpida que permeta la seva consulta com si es tractés d'un manual, sense necessitat de llegir la totalitat del document. En resum, en aquest estudi es detallen els mètodes i procediments de la investigació realitzada amb pacients de càncer de pròstata i hiperplàsia benigna de pròstata amb el propòsit d'aconseguir un prototip d'un nas electrònic per a la classificació de pacients fent ús d'orina com a bio-fluid. S'ha tractat d'escriure una referència des d'on seguir construint coneixement al voltant dels nassos electrònics aplicats a la classificació de pacients. / [EN] Finding a reliable non-invasive classification method to distinguish between patients with prostate cancer and benign prostatic hyperplasia is not a trivial task. The most commonly used specific prostate antigen shows an increase in other situations such as urinary retention or ejaculation. Cellular metabolic products, such as volatile compounds in the form of bio- fiuids, present an opportunity to study them by using metal oxide semiconduc- tor technology. An electronic nose designed for these bio-fiuids could become a key ambulatory test in order to decrease the number of biopsies. The strategy of the work is configured in diferent fields. Design a 3D set to enclose the electronics and penumatic circuits. The suitability of the samples it has to be studied furthermore the creation of a standardized database for electronic noses to store these samples. The definition of a friendly user interface for the health professional besides a system secured for communication with a data storage server. To sum up, all the software and hardware necessary to make viable the democratization of electronic noses in hospital care. In addition, the method be inployed to increase the number of data has been decisive to simplify the training of the neural network with which an accuracy of 87% has been achieved in the classification between prostate cancer patients and benign prostatic hyperplasia. A book format has been chosen to collect all the significant points of the study. The first chapter focuses on the thesis project to be financed, the problem to be solved, the objectives and the work plan. The second chapter defines the concepts, the sense of smell, the bladder, the prostate, the sensors used, cancer indicators and other elements such as the electronic nose. It is with an electronic nose that the signals discussed in chapter three are obtained. This chapter shows the characteristics of signals from patients with prostate cancer and patients with benign prostatic hyper- plasia, their treatment, filtering, comparison and use for patient classification. Likewise, two different methods of classification and study of the algorithms to automate the same are shown. The fourth chapter focuses on the construction of a prototype. This chapter has been approached as a construction manual that allows the reader to know the process carried out, the decision-making and the technique used to make both the hardware, the software and the 3D. Since the diversity of specialties that converge in the same project can make it impossible to master any of the fields discussed, including within the same field of specialization, this chapter has been prepared with diagrams and source code that accompanies the explanations of form detailed. The purpose of this chapter is to allow researchers from various areas of knowledge to construct it without the need to delve into other fields. In addition, this chapter details the procedures to promote the democratization of the electronic nose as a scientific instrument and with the hope of providing the basis for future implementations in the scientific community. For the author, the thesis is not just a document, it is a period of personal evolution. It has been conditioned by various factors, a pandemic, the initial approach, the funding, the host group, the line of research, the socioof the author and the self-learning in the execution process. That is why what has been shaped in the fifth has guided in one way or another, but in a significant way, the decision-making. This chapter deals with future work and three projects, COST and H2020, DE1-SoC ADC eNose and Tumor Detection, which have influenced the development of the thesis. It is an exercise in reflection about them and they are a sample of the author's research capacity. The conclusions are collected in chapter six. However, each chapter has a section called "Reflections" where those specific ideas and conclusions about the same are noted. / Talens Felis, JB. (2022). Anàlisi, disseny i implementació d'instrumentació no invasiva per a la detecció de càncer de pròstata i bufeta mitjançant tecnologia MOS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/190835

No description available.

Transmission of video content over wireless access networks (in particular, Wireless Local Area Networks (WLAN) and Third Generation Universal Mobile Telecommunication System (3G UMTS)) is growing exponentially and gaining popularity, and is predicted to expose new revenue streams for mobile network operators. However, the success of these video applications over wireless access networks very much depend on meeting the user’s Quality of Service (QoS) requirements. Thus, it is highly desirable to be able to predict and, if appropriate, to control video quality to meet user’s QoS requirements. Video quality is affected by distortions caused by the encoder and the wireless access network. The impact of these distortions is content dependent, but this feature has not been widely used in existing video quality prediction models. The main aim of the project is the development of novel and efficient models for video quality prediction in a non-intrusive way for low bitrate and resolution videos and to demonstrate their application in QoS-driven adaptation schemes for mobile video streaming applications. This led to five main contributions of the thesis as follows:(1) A thorough understanding of the relationships between video quality, wireless access network (UMTS and WLAN) parameters (e.g. packet/block loss, mean burst length and link bandwidth), encoder parameters (e.g. sender bitrate, frame rate) and content type is provided. An understanding of the relationships and interactions between them and their impact on video quality is important as it provides a basis for the development of non-intrusive video quality prediction models.(2) A new content classification method was proposed based on statistical tools as content type was found to be the most important parameter. (3) Efficient regression-based and artificial neural network-based learning models were developed for video quality prediction over WLAN and UMTS access networks. The models are light weight (can be implemented in real time monitoring), provide a measure for user perceived quality, without time consuming subjective tests. The models have potential applications in several other areas, including QoS control and optimization in network planning and content provisioning for network/service providers.(4) The applications of the proposed regression-based models were investigated in (i) optimization of content provisioning and network resource utilization and (ii) A new fuzzy sender bitrate adaptation scheme was presented at the sender side over WLAN and UMTS access networks. (5) Finally, Internet-based subjective tests that captured distortions caused by the encoder and the wireless access network for different types of contents were designed. The database of subjective results has been made available to research community as there is a lack of subjective video quality assessment databases.

Doctor of Philosophy / Department of Chemical Engineering / James H. Edgar / The integration of high-κ dielectrics with silicon and III-V semiconductors is important due to the need for high speed and high power electronic devices. The purpose of this research was to find the best conditions for fabricating high-κ dielectrics (oxides) on GaN or Si. In particular high-κ oxides can sustain the high breakdown electric field of GaN and utilize the excellent properties of GaN. This research developed an understanding of how process conditions impact the properties of high-κ dielectric on Si and GaN. Thermal and plasma-assisted atomic layer deposition (ALD) was employed to deposit TiO₂ on Si and Al₂O₃ on polar (c-plane) GaN at optimized temperatures of 200°C and 280°C respectively. The semiconductor surface treatment before ALD and the deposition temperature have a strong impact on the dielectric’s electrical properties, surface morphology, stoichiometry, and impurity concentration. Of several etches considered, cleaning the GaN with a piranha etch produced Al₂O₃/GaN MOS capacitors with the best electrical characteristics. The benefits of growing a native oxide of GaN by dry thermal oxidation before depositing the high-κ dielectric was also investigated; oxidizing at 850°C for 30 minutes resulted in the best dielectric-semiconductor interface quality. Interest in nonpolar (m-plane) GaN (due to its lack of strong polarization field) motivated an investigation into the temperature behavior of Al₂O₃/m-plane GaN MOS capacitors. Nonpolar GaN MOS capacitors exhibited a stable flatband voltage across the measured temperature range and demonstrated temperature-stable operation.

Foram estudados filmes de oxinitreto de silício obtidos por PECVD à 320°C, a partir da mistura gasosa de N2O+SiH4+He, com diferentes valores de pressão e potência de deposição com o objetivo de produzir boa qualidade de interface deste material com o Si e de obter uma baixa densidade de carga efetiva visando a aplicação desses filmes em dispositivos semicondutores MOS. Os resultados mostraram que com uma pressão de deposição de 0,160 mbar e potências menores que 125 W/cm2 é possível obter um valor de densidade de estados de interface (Dit) de 4x1010 eV-1.cm-2, campo elétrico de ruptura (Ebd) de 13 MV/cm, valores comparáveis ao SiO2 térmico e uma densidade de carga efetiva (Nss) de 4x1011 cm-2. Segundo resultados experimentais esse valor de Nss é o mínimo possível que se pode atingir com a limpeza química utilizada em nosso laboratório. Pode-se dizer que estes são resultados bastante interessantes considerando que se trata de um material obtido por PECVD à baixa temperatura, porém viável para aplicação em dispositivos MOS. Iniciando os estudos com dielétricos de maiores valores de constante dielétrica optamos por estudar filmes de TiOx (k=40-100), obtidos por sputtering reativo, a partir da mistura gasosa de Ar+O2 e utilizando alvo de Ti. Foram fabricados capacitores MOS com estes filmes e obteve-se valores de constante dielétrica que variaram de 40-160. Porém esses materiais ainda apresentavam valores apreciáveis de corrente de fuga que foram minimizadas em ordens de grandeza quando utilizados dielétricos de dupla camada com SiO2 ou SiOxNy (otimizado neste trabalho) na interface, além de se observar uma melhora significativa da qualidade de interface. Utilizando dupla camada dielétrica com filmes de SiOxNy e SiO2, ainda espessos (³ 1nm) para camada intermediária, obteve-se uma constante dielétrica efetiva em torno de 20. Vale ressaltar que os dois filmes SiOxNy e TiOx, conseqüentemente a dupla camada, foram fabricados a baixas temperaturas. / Silicon oxynitride films obtained by the PECVD technique from N2O+SiH4+He gaseous mixtures, at 320°C, with different deposition pressure and RF power were studied intending to improve the interface quality with Si, decreasing the effective charge density and the interface state density in order to utilize them in MOS semiconductor devices. The results showed that with a deposition pressure of 0.160 mbar and a RF power density lower than 125 W/cm2 it is possible to obtain interface state density (Dit) values of 4x1010 eV-1.cm-2, Electrical Breakdown (Ebd) of 13 MV/cm, comparable with the obtained for thermally grown SiO2 , and an effective charge density (Nss) of 4x1011 cm-2. According with experimental results this Nss value is the minimum attainable with our chemical cleaning process. In this way it can be said that these results are very promising, considering that these materials were obtained by PECVD at low temperatures, but still viable for MOS devices application. In order to initiate studies with high dielectrics constant material, TiOx films (k= 40-180), obtained by reactive sputtering through the Ar+O2 gaseous mixture utilizing a Ti target, were chosen. MOS capacitors with these films were fabricated and dielectric constant values varying from 40 to 160 were obtained. However, until now, these materials have presented appreciable leakage current values, which were, minimize by orders of magnitude with the addition of a thin SiO2 or SiOxNy (optimized in this work) layer at the interface were utilized. This thin layer also resulted in a significant improvement of the interface quality. Utilizing double dielectric layer with SiOxNy or SiO2, still thick (³ 1nm) as intermediate layer a dielectric constant value of 20 was obtained. Its important to mention that the SiOxNy and TiOx films, and consequently the double layer, were deposited at low temperatures.

O presente trabalho teve como objetivo a modelagem de células solares MOS operando em regime de inversão controlado por centros positivamente carregados na interface SiNxOy/Si. Este tipo de célula solar foi recentemente fabricada pela primeira vez no âmbito dos trabalhos desenvolvidos no grupo de Superfícies, Interfaces e Deposição Eletroquímica (GSIDE) do LSI/PSI/EPUSP utilizando dielétricos de porta ultra-finos (~2nm). A receita de crescimento de dielétrico ultra-fino desenvolvida foi no sentido de assegurar reprodutibilidade e uniformidade da espessura do dielétrico ao longo de áreas extensas de alguns cm2. Baseado nas curvas experimentais CxVg, GxVg e IxVg das células solares fabricadas, foi mostrado para as células fabricadas em substrato tipo P que existem os centros K predominantemente preenchidos com cargas positivas em todos os regimes de operação (acumulação, depleção e inversão). A densidade de cargas positivas (Qiq) na interface SiNxOy/Si além de ter resultado positivo, apresentou um comportamento linear com o potencial de superfície (ys) ou com a tensão de porta Vg de acordo com os resultados obtidos através de um simulador numérico desenvolvido para esta aplicação específica. Tal comportamento consistiu no acomodamento das cargas positivas na interface de forma que uma região de depleção profunda (Wd) é formada sem a presença da camada de inversão na condição sem iluminação. Para as células MOS submetidas a diferentes níveis de iluminação, tanto para os dielétricos crescidos a 850oC como também para aqueles que foram crescidos a 700oC, foi constatado que os centros K na interface funcionam como uma região de armazenamento de cargas positivas a medida em que os elétrons tunelam em direção à porta metálica da estrutura MOS. Como resultado, este tipo de comportamento significa uma nova forma de implementar o efeito fotovoltáico. / The goal of the present work was the modeling of MOS solar cells operating in an inversion regime controlled by positively charged centers at the SiNxOy interface. This type of solar cell was recently manufactured for the first time in the activities developed in the group of Surfaces, Interfaces and Electrochemical Deposition (GSIDE) from LSI/PSI/EPUSP using ultra-thin gate dielectrics (~2nm). The recipe for the growth of ultra-thin dielectrics was developed to ensure reproducibility and uniformity of the dielectrics thickness over large areas of few square centimeters. Based on the experimental curves CxVg, GxVg e IxVg of the manufactured MOS solar cells, it was shown for cells manufactured in P-type substrate that there are K centers dominantly filled with positive charges in all operating regimes (accumulation, depletion and inversion). The positive charge density (Qiq) at the SiNxOy/Si interface, in addition to having a positive charge, presented a linear behaviour with the surface potential (ys) or with the gate voltage (Vg) according to the results obtained from a numerical simulator developed for this application. Such behavior consisted of accommodating the positive charges at the SiNxOy/Si interface so that a deep depletion region (Wd) is formed without the presence of the inversion layer in the condition without illumination. For MOS cells subjected to different levels of illumination, both for dielectrics grown at 850oC as well as for those grown at 700oC, it was found that the K centers at the SiNxOy/Si interface work as a region of positive charge storage as the electrons tunnel from the interface towards the metal gate of the MOS cells. As a result, this type of behaviour means a new way of implementing the photovoltaic effect.

Foram estudados filmes de oxinitreto de silício obtidos por PECVD à 320°C, a partir da mistura gasosa de N2O+SiH4+He, com diferentes valores de pressão e potência de deposição com o objetivo de produzir boa qualidade de interface deste material com o Si e de obter uma baixa densidade de carga efetiva visando a aplicação desses filmes em dispositivos semicondutores MOS. Os resultados mostraram que com uma pressão de deposição de 0,160 mbar e potências menores que 125 W/cm2 é possível obter um valor de densidade de estados de interface (Dit) de 4x1010 eV-1.cm-2, campo elétrico de ruptura (Ebd) de 13 MV/cm, valores comparáveis ao SiO2 térmico e uma densidade de carga efetiva (Nss) de 4x1011 cm-2. Segundo resultados experimentais esse valor de Nss é o mínimo possível que se pode atingir com a limpeza química utilizada em nosso laboratório. Pode-se dizer que estes são resultados bastante interessantes considerando que se trata de um material obtido por PECVD à baixa temperatura, porém viável para aplicação em dispositivos MOS. Iniciando os estudos com dielétricos de maiores valores de constante dielétrica optamos por estudar filmes de TiOx (k=40-100), obtidos por sputtering reativo, a partir da mistura gasosa de Ar+O2 e utilizando alvo de Ti. Foram fabricados capacitores MOS com estes filmes e obteve-se valores de constante dielétrica que variaram de 40-160. Porém esses materiais ainda apresentavam valores apreciáveis de corrente de fuga que foram minimizadas em ordens de grandeza quando utilizados dielétricos de dupla camada com SiO2 ou SiOxNy (otimizado neste trabalho) na interface, além de se observar uma melhora significativa da qualidade de interface. Utilizando dupla camada dielétrica com filmes de SiOxNy e SiO2, ainda espessos (³ 1nm) para camada intermediária, obteve-se uma constante dielétrica efetiva em torno de 20. Vale ressaltar que os dois filmes SiOxNy e TiOx, conseqüentemente a dupla camada, foram fabricados a baixas temperaturas. / Silicon oxynitride films obtained by the PECVD technique from N2O+SiH4+He gaseous mixtures, at 320°C, with different deposition pressure and RF power were studied intending to improve the interface quality with Si, decreasing the effective charge density and the interface state density in order to utilize them in MOS semiconductor devices. The results showed that with a deposition pressure of 0.160 mbar and a RF power density lower than 125 W/cm2 it is possible to obtain interface state density (Dit) values of 4x1010 eV-1.cm-2, Electrical Breakdown (Ebd) of 13 MV/cm, comparable with the obtained for thermally grown SiO2 , and an effective charge density (Nss) of 4x1011 cm-2. According with experimental results this Nss value is the minimum attainable with our chemical cleaning process. In this way it can be said that these results are very promising, considering that these materials were obtained by PECVD at low temperatures, but still viable for MOS devices application. In order to initiate studies with high dielectrics constant material, TiOx films (k= 40-180), obtained by reactive sputtering through the Ar+O2 gaseous mixture utilizing a Ti target, were chosen. MOS capacitors with these films were fabricated and dielectric constant values varying from 40 to 160 were obtained. However, until now, these materials have presented appreciable leakage current values, which were, minimize by orders of magnitude with the addition of a thin SiO2 or SiOxNy (optimized in this work) layer at the interface were utilized. This thin layer also resulted in a significant improvement of the interface quality. Utilizing double dielectric layer with SiOxNy or SiO2, still thick (³ 1nm) as intermediate layer a dielectric constant value of 20 was obtained. Its important to mention that the SiOxNy and TiOx films, and consequently the double layer, were deposited at low temperatures.