A full electro-thermal simulation of a three-phase space-vector-modulated (SVM) inverter is performed and validated with measurements. Electrical parameters are extracted over temperature for the insulated gate bipolar transistor (IGBT) and diode electro-thermal models. A thermal network methodology that includes thermal coupling between devices is applied to a six-pack module package containing multiple IGBT and diode chips. The electro-thermal device models and six-pack module thermal model are used to simulate SVM inverter operation at several power levels. Good agreement between model and measurement is obtained for steady state operation of the three-phase inverter. In addition, transient heating of a single IGBT in the six-pack module is modeled and validated, yielding good agreement. / Master of Science

The temperature dependent electrical characteristics of silicon carbide power transistors – 4H-SiC metal semiconductor field-effect transistors (MESFETs) and 4H-SiC bipolar junction transistors (BJTs) have been investigated through simulation and experimental approaches. Junction temperatures and temperature distributions in devices under large power densities have been estimated. The DC and RF performance of 4H-SiC RF Power MESFETs have been studied through two-dimensional electro-thermal simulations using commercial software MEDICI and ISE. The simulated characteristics of the transistors were compared with the measurement results. Performance degradation of transistors under self-heating and high operating temperatures have been analyzed in terms of gate and drain characteristics, power density, high frequency current gain and power gain. 3D thermal simulations have been performed for single and multi-finger MESFETs and the simulated junction temperatures and temperature profiles were compared with the results from electro-thermal simulations. The reduction in drain current caused by self-heating was found to be more prominent for transistors with more fingers and it imposes a limitation on both the output power and the power density (in W/mm) of multi-fingered large area devices. Thermal issues for design of high power multi-fingered SiC MESFETs were also investigated. A couple of useful ways to reduce the self-heating effects were discussed. Trap-induced performance instabilities of the devices were analyzed by carrying out DC, transient, and pulse measurements at room and elevated temperatures. Electrical characteristics of 4H-SiC BJTs have been measured. A reduction in current gain at elevated temperatures was observed. Based on the collector current-voltage diagram measured at three different ambient temperatures the junction temperature was extracted using the assumption that the current gain only depends on the temperature. Temperature measurements have been carried out for SiC BJTs. Thermal images of a device under operation were recorded using an infrared camera. 3D thermal simulations were conducted using FEMLAB. Both the simulations and the measurement showed a significant temperature increase in the vicinity of the device when operated at high power densities, thus causing the decrease of the DC current gain. The junction temperatures obtained from the thermal imaging, simulation and extraction agree well.

<p>The temperature dependent electrical characteristics of silicon carbide power transistors – 4H-SiC metal semiconductor field-effect transistors (MESFETs) and 4H-SiC bipolar junction transistors (BJTs) have been investigated through simulation and experimental approaches. Junction temperatures and temperature distributions in devices under large power densities have been estimated. </p><p>The DC and RF performance of 4H-SiC RF Power MESFETs have been studied through two-dimensional electro-thermal simulations using commercial software MEDICI and ISE. The simulated characteristics of the transistors were compared with the measurement results. Performance degradation of transistors under self-heating and high operating temperatures have been analyzed in terms of gate and drain characteristics, power density, high frequency current gain and power gain. 3D thermal simulations have been performed for single and multi-finger MESFETs and the simulated junction temperatures and temperature profiles were compared with the results from electro-thermal simulations. The reduction in drain current caused by self-heating was found to be more prominent for transistors with more fingers and it imposes a limitation on both the output power and the power density (in W/mm) of multi-fingered large area devices. Thermal issues for design of high power multi-fingered SiC MESFETs were also investigated. A couple of useful ways to reduce the self-heating effects were discussed. Trap-induced performance instabilities of the devices were analyzed by carrying out DC, transient, and pulse measurements at room and elevated temperatures. </p><p>Electrical characteristics of 4H-SiC BJTs have been measured. A reduction in current gain at elevated temperatures was observed. Based on the collector current-voltage diagram measured at three different ambient temperatures the junction temperature was extracted using the assumption that the current gain only depends on the temperature. Temperature measurements have been carried out for SiC BJTs. Thermal images of a device under operation were recorded using an infrared camera. 3D thermal simulations were conducted using FEMLAB. Both the simulations and the measurement showed a significant temperature increase in the vicinity of the device when operated at high power densities, thus causing the decrease of the DC current gain. The junction temperatures obtained from the thermal imaging, simulation and extraction agree well. </p>

Une forte exigence de robustesse s’est imposée dans tous les domaines d’application des composants de puissance. Dans ce cadre très contraint, seule une analyse fine des phénomènes liés directement ou indirectement aux défaillances peut garantir une maîtrise de la fiabilité des fonctions assurées par les nouveaux composants de puissance. Cependant, ces phénomènes impliquent des couplages entre des effets électriques, thermiques et mécaniques, rendant leur étude très complexe. Le recours à la modélisation multi-physique bien adaptée s’avère alors déterminant. Dans ce mémoire de thèse, nous proposons une méthodologie de modélisation électrique prenant en compte les effets de la température sur les phénomènes localisés qui initient une défaillance souvent fatale. En prévision de la simulation électrothermique couplée impliquant des transistors MOS de puissance, un modèle électrique thermosensible de ce composant et de sa diode structurelle a été développé. Corrélativement un ensemble de bancs expérimentaux a été mis en œuvre pour l’extraction des paramètres et pour la validation du modèle. Une attention particulière a été accordée à l’étude des phénomènes parasites qui pourraient survenir de manière très localisée suite à une répartition inhomogène de la température et à l’apparition de points chauds. Ainsi les fonctionnements limites en avalanche, avec le déclenchement du transistor bipolaire parasite et de son retournement ont été modélisés. Des bancs spécifiques pour la validation du modèle pour les régimes extrêmes ont été utilisés en prenant des précautions liées à la haute température. Enfin, Le modèle électrique thermosensible complet développé a été utilisé par la société Epsilon ingénierie pour faire des simulations électrothermiques du MOS de puissance en mode d’avalanche en adaptant le logiciel Epsilon-R3D / Strong demand for robustness has emerged in all areas of application of power components.Only a detailed analysis of phenomena related directly or indirectly to failures can ensure thereliability of the functions of the new power components. However, these phenomena involvethe coupling between electrical effects, thermal and mechanical, making their study verycomplex. The use of multi-physics modeling is well suited when determining. In this thesis,we propose a methodology for electrical modeling taking into account the effects of temperatureon the localized phenomena that initiate failure is often fatal. In preparation for thecoupled electro-thermal simulation involving MOS power transistors, an electric thermosensitivemodel of the MOS and its body diode has been developed. Correspondingly a set ofexperimental studies was implemented to extract the parameters and model validation. Particularattention was paid to the study of interference phenomena that could occur in a localizedresponse to an inhomogeneous distribution of temperature and hot spots. Thus the workingslimits avalanche, with the outbreak of parasitic bipolar transistor (snapback) and its reversalwere modeled. Benches specific validations of the model for harsh switching conditions wereused by taking precautions related to high temperature. Finally, the complete thermal electricmodel developed was used by the company “EPSILON Ingénierie” for electro-thermal simulationof power MOS mode Avalanche Software adapting Epsilon-R3D.

Une forte exigence de robustesse s'est imposée dans tous les domaines d'application des composants de puissance. Dans ce cadre très contraint, seule une analyse fine des phénomènes liés directement ou indirectement aux défaillances peut garantir une maîtrise de la fiabilité des fonctions assurées par les nouveaux composants de puissance. Cependant, ces phénomènes impliquent des couplages entre des effets électriques, thermiques et mécaniques, rendant leur étude très complexe. Le recours à la modélisation multi-physique bien adaptée s'avère alors déterminant. Dans ce mémoire de thèse, nous proposons une méthodologie de modélisation électrique prenant en compte les effets de la température sur les phénomènes localisés qui initient une défaillance souvent fatale. En prévision de la simulation électrothermique couplée impliquant des transistors MOS de puissance, un modèle électrique thermosensible de ce composant et de sa diode structurelle a été développé. Corrélativement un ensemble de bancs expérimentaux a été mis en oeuvre pour l'extraction des paramètres et pour la validation du modèle. Une attention particulière a été accordée à l'étude des phénomènes parasites qui pourraient survenir de manière très localisée suite à une répartition inhomogène de la température et à l'apparition de points chauds. Ainsi les fonctionnements limites en avalanche, avec le déclenchement du transistor bipolaire parasite et de son retournement ont été modélisés. Des bancs spécifiques pour la validation du modèle pour les régimes extrêmes ont été utilisés en prenant des précautions liées à la haute température. Enfin, Le modèle électrique thermosensible complet développé a été utilisé par la société EPSILON Ingénierie pour faire des simulations électrothermiques du MOS de puissance en mode d'avalanche en adaptant le logiciel Epsilon-R3D.

Recently, there has been an increasing interest in the electronics world for those aspects related to semiconducting gas sensor (SGS) materials. In view of the increasingly strict legal limits for pollutant gas emissions, there is a great interest in developing high performance gas sensors for applications such as controlling air pollution and exhaust gases in automotive industry. In this way, semiconductor gas sensors offer good advantages with respect to other gas sensor devices, due to their simple implementation, low cost and good stability and sensitivity. The first part of the thesis is dedicated to the synthesis, film structural and sensitivity study of the Tin Oxide film deposited by RF sputtering, doped with noble metal Palladium (Pd). Effects on the Gas Sensitivity due to the deposition parameters like thickness of the film, Substrate temperature, Ar /O2 ratio of the sputtering environment, annealing temperature and duration and doping metal weight % into the Tin Oxide films are studied and the results are shown in detail. The sensitivity and selectivity of the gas sensing film is decided by the operating temperature i.e. the temperature of the gas sensing film while it is in the target gas ambience, Microheaters happen to be the very important component in the gas sensor especially with wide band gap semiconducting metal oxides films such as tin oxide, gallium oxide or indium oxides. Other than gas sensing microheater also finds applications in many areas like thermal dip pen nanolithography, polymerase chain reaction (PCR), fluid pumping with bubbles, in vitro fertilization etc. So in this report due importance was given for the design and fabrication of the microheater. Microheaters are the most power consuming element of the integrated Gas sensors. This is also an important reason for the extensive microheater work in this research. Six different heater patterns were simulated by considering low power and temperature uniformity as an important goals. Among them the best three patterns named Double spiral, “Fan” Shape and “S” shape were chosen for fabrication and both thermal and electrical characterization results of them were presented in detail in the Microheater section of the thesis. It is believed that the intelligent design and integration of the electronic circuitry (for drive, signal conditioning/compensation, and read-out) with the gas sensing element can mitigate some of the significant issues inherent in solid-state gas sensors, such as strong temperature and humidity dependence, signal drift, aging, poisoning, and weak selectivity. The sensitivity of the gas sensors which has been indicated as the dynamic change of resistance in wide range should be read out properly. Towards this aim a low cast high efficient readout circuit is designed and implemented. Temperature monitoring and controlling is a key phenomenon in the metal Oxide based gas sensors since the selectivity mainly depends on the operating temperature of the sensing film. So focus was also shown on the design and implementation of the temperature monitoring and control unit, which been presented in the last part of this thesis.

Eine wichtige Eigenschaft von Leistungsdioden ist ihre Stoßstromrobustheit, also die Fähigkeit, einem kurzeitigen hohen Strom standzuhalten. Bei Dioden aus SiC wird dabei häufig auf die MPS-Struktur zurückgegriffen. In dieser Arbeit wird das Stoßstromverhalten von neuen 1200V-SiC-MPS-Dioden von Infineon untersucht. Dabei wird gemessen, welchem Strom die Dioden bei einem Halbsinus-Puls von 10ms standhalten. Das Ergebnis wird mit der Robustheit herkömmlicher SiC-Schottky-Dioden verglichen. Die Stoßstromrobustheit bei Parallelschaltung wird untersucht. Mittels elektro-thermischer Simulationen werden Möglichkeiten zur Verbesserung der Stoßstromrobustheit der Dioden erörtert. Hierbei wird die Schichtdicke erhöht und Kupfer statt Aluminium als Anodenmetallisierung angenommen. Des Weiteren wird das Simulationsmodell hinsichtlich der Lotschicht und eines reduzierten SiC-Substrats variiert. Die MPS-Dioden weisen bei hohem Strom einen negativen differentiellen Widerstand auf, hervorgerufen durch die Injektion von Minoritätsladungsträgern aus den p-dotierten Gebieten. Die Aktivierung der Injektion von Minoritätsladungsträgern in Abhängigkeit der Größe der p-dotierten Gebiete wird ebenfalls mittels Simulationen untersucht. Ein Vergleich verschiedener Caughey-Thomas-Parameter zur Modellierung der Ladungsträgermobilität in FEM-Bauelementsimulatoren wird durchgeführt. Das Ausschaltverhalten der MPS-Dioden wird unter verschiedenen Bedingungen gemessen. Dazu zählen das Abschalten unter Anwendungsbedingungen, das Abschalten unter Überlast von bis zum fünfzehnfachen Nennstrom, das Abschalten mit hohen Strom- und Spannungssteilheiten und das Abschalten in Parallelschaltung und mit zusätzlicher parasitärer Induktivität. Die Untersuchungen zeigen eine hohe Robustheit der neuen 1200V-SiC-MPS-Dioden. / The surge current ruggedness is an import property of power diodes. In case of SiC diodes this is realized by a Merged-pin-Schottky (MPS) structure. In this thesis the surge current ruggedness of novel 1200V SiC MPS diodes from Infineon is investigated. The maximum current during a half sine surge current pulse of 10ms is determined in measurements for various diodes and compared to the surge current ruggedness of conventional Schottky diodes. Furthermore, the surge current ruggedness in parallel arrangement is measured. By the means of electro-thermal simulations options to improve the surge current ruggedness are investigated. The simulation model is varied concerning the diodes anode metalization layer thickness and material. The layer thickness is increased and the typical aluminum is replaced by copper. Additionally, the influence of the silicon carbide substrate thickness and the solder layer thickness and material on the surge current ruggedness is simulated. The MPS diodes possess a negative differential resistance at high currents caused by the injection of minority carriers by the p-doped regions. The injection of minority carriers in dependence of the size of the p-regions is also examined in simulations. Furthermore, different parameter sets of the the Caughey-Thomas formula to describe the carrier mobility are compared. The turn-off behavior of the diodes is measured under different conditions such as the turn-off from fifteen times the rated current, the turn-off with high current and voltage slopes and the turn-off in parallel arrangement and with additional inductance. The investigation show a high robustness of the novel 1200V SiC MPS diodes.