190 research outputs found
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Tohoku UniversityçŠćł¶èȘćČèȘČ
Chip- and System-Level Reliability on SiC-based Power Modules
The blocking voltage, switching frequency and temperature tolerance of power devices have been greatly improved due to the revolution of wide bandgap (WBG) materials, such as silicon carbide (SiC) and gallium nitride (GaN). Owing to the development of SiC-based power devices, the power rating, operating voltage, and power density of power modules have been significantly improved. However, the reliability of SiC-based power modules has not been fully explored yet. Thus, this dissertation focuses on the chip- and system-level reliability on SiC-based power modules. For chip-level reliability, this work focuses on on-chip SiC ESD protection devices for SiC-based integrated circuits (ICs). In order to develop SiC ESD protection devices, SiC-based Ohmic contact and ion implantation have been studied. Nickel/Titanium/Aluminum (Ni/Ti/Al) metal stacks were deposited on SiC substrates to form Ohmic contact. Circular transfer length method (CTLM) structures were fabricated to characterize contact resistivity. Ion implantation was designed and simulated by Sentraurus technology computer aided design (TCAD) software. Secondary-ion mass spectrometry (SIMS) results show a good match with the simulation results. In addition, SiC ESD protection devices, such as N-type metal-oxide-semiconductor (NMOS), laterally diffused metal-oxide-semiconductor (LDMOS), high-voltage silicon controlled rectifier (HV-SCR) and low-voltage silicon controlled rectifier (LV-SCR), have been designed. Transmission line pulse (TLP) and very fast TLP (VF-TLP) measurements were carried out to characterize their ESD performance. The proposed SiC-based HV-SCR shows the highest failure current on TLP measurement and can be used as an area-efficient ESD protection device. On the other hand, for system-level reliability, this dissertation focuses on the galvanic isolation of high-temperature SiC power modules. Low temperature co-fired ceramics (LTCC) based high-temperature optocouplers were designed and fabricated as galvanic isolators. The LTCC-based high-temperature optocouplers show promising driving capability and steady response speed from 25 ÂșC to 250 ÂșC. In order to verify the performance of the high-temperature optocouplers at the system level, LTCC-based gate drivers that utilize the high-temperature optocouplers as galvanic isolators were designed and integrated into a high-temperature SiC-based power module. Finally, the high-temperature power module with integrated LTCC-based gate drivers was characterized by DPTs from 25 ÂșC to 200 ÂșC. The power module shows reliable switching performance at elevated temperatures
Outdoor Insulation and Gas Insulated Switchgears
This book focuses on theoretical and practical developments in the performance of high-voltage transmission line against atmospheric pollution and icing. Modifications using suitable fillers are also pinpointed to improve silicone rubber insulation materials. Very fast transient overvoltage (VFTO) mitigation techniques, along with some suggestions for reliable partial discharge measurements under DC voltage stresses inside gas-insulated switchgears, are addressed. The application of an inductor-based filter for the protective performance of surge arresters against indirect lightning strikes is also discussed
Thermal Analysis and Junction Temperature Estimation under Different Ambient Temperatures Considering Convection Thermal Coupling between Power Devices
The convection thermal coupling between adjacent power devices in power converters is dependent on the ambient temperature. When the ambient temperature changes, the convection thermal coupling also changes. This results in an inaccurate thermal model that causes errors in the prediction of the thermal distribution and junction temperature based on a fixed ambient temperature for power devices in converters application. To solve this variable-ambient-temperature-related issue, a thermal coupling experiment for semiconductor power devices (the MOSFET and diode) was performed to discuss the influence of the thermal coupling effect between adjacent devices and the FEM (Finite Element Method) thermal models for the power devices considering the convection thermal coupling are established. Through these simulations, the junction temperatures of devices under different ambient temperatures were obtained, and the relationships between the junction temperature and ambient temperatures were established. Moreover, the junction temperatures of power devices under different ambient temperatures were calculated and temperature distributions are analyzed in this paper. This method shows a strong significance and has potential applications for high-efficiency and high-power density converter designs
Chip- and System-Level Reliability on SiC-based Power Modules
The blocking voltage, switching frequency and temperature tolerance of power devices have been greatly improved due to the revolution of wide bandgap (WBG) materials, such as silicon carbide (SiC) and gallium nitride (GaN). Owing to the development of SiC-based power devices, the power rating, operating voltage, and power density of power modules have been significantly improved. However, the reliability of SiC-based power modules has not been fully explored yet. Thus, this dissertation focuses on the chip- and system-level reliability on SiC-based power modules. For chip-level reliability, this work focuses on on-chip SiC ESD protection devices for SiC-based integrated circuits (ICs). In order to develop SiC ESD protection devices, SiC-based Ohmic contact and ion implantation have been studied. Nickel/Titanium/Aluminum (Ni/Ti/Al) metal stacks were deposited on SiC substrates to form Ohmic contact. Circular transfer length method (CTLM) structures were fabricated to characterize contact resistivity. Ion implantation was designed and simulated by Sentraurus technology computer aided design (TCAD) software. Secondary-ion mass spectrometry (SIMS) results show a good match with the simulation results. In addition, SiC ESD protection devices, such as N-type metal-oxide-semiconductor (NMOS), laterally diffused metal-oxide-semiconductor (LDMOS), high-voltage silicon controlled rectifier (HV-SCR) and low-voltage silicon controlled rectifier (LV-SCR), have been designed. Transmission line pulse (TLP) and very fast TLP (VF-TLP) measurements were carried out to characterize their ESD performance. The proposed SiC-based HV-SCR shows the highest failure current on TLP measurement and can be used as an area-efficient ESD protection device. On the other hand, for system-level reliability, this dissertation focuses on the galvanic isolation of high-temperature SiC power modules. Low temperature co-fired ceramics (LTCC) based high-temperature optocouplers were designed and fabricated as galvanic isolators. The LTCC-based high-temperature optocouplers show promising driving capability and steady response speed from 25 ÂșC to 250 ÂșC. In order to verify the performance of the high-temperature optocouplers at the system level, LTCC-based gate drivers that utilize the high-temperature optocouplers as galvanic isolators were designed and integrated into a high-temperature SiC-based power module. Finally, the high-temperature power module with integrated LTCC-based gate drivers was characterized by DPTs from 25 ÂșC to 200 ÂșC. The power module shows reliable switching performance at elevated temperatures
Measurements and review of failure mechanisms and reliability constraints of 4H-SiC Power MOSFETs under short circuit events
The reliability of the SiC MOSFET has always been a factor hindering the device application, especially under high voltage and high current conditions, such as in the short circuit events. This paper experimentally reviews the failure mechanisms caused by destructive short circuit impulses, and investigates the degradation patterns of key electrical parameters under repetitive short circuit events. The impact of test parameters on the short circuit reliability of SiC MOSFET has been analyzed. Approaches to characterize the electrical-thermal-mechanical stress during the short circuit period and advanced test methods are highlighted. Finally, the constraints from the standpoint of both manufacturers and users have been presented, including comparison of current SiC MOSFET devices, reliability evaluation of parallel SiC MOSFET devices, reliability improvement of the chip, performance improvement of protection circuits, and reliability assessment of SiC MOSFET devices under application-representative stress
Challenges and New Trends in Power Electronic Devices Reliability
The rapid increase in new power electronic devices and converters for electric transportation and smart grid technologies requires a deepanalysis of their component performances, considering all of the different environmental scenarios, overload conditions, and high stressoperations. Therefore, evaluation of the reliability and availability of these devices becomes fundamental both from technical and economicalpoints of view. The rapid evolution of technologies and the high reliability level offered by these components have shown that estimating reliability through the traditional approaches is difficult, as historical failure data and/or past observed scenarios demonstrate. With the aim topropose new approaches for the evaluation of reliability, in this book, eleven innovative contributions are collected, all focusedon the reliability assessment of power electronic devices and related components
OberflĂ€chenemittierende Laser mit vertikaler KavitĂ€t (VCSELs) und VCSEL-Arrays fĂŒr Kommunikation und Sensorik
Future generations of optical wireless communication and sensing systems require compact, low-cost, reliable, and highly efficient light sources capable of transmitting modulated beams across free space at gigabit per second (Gbps) data rates and pulsed beams with sub-nanosecond rise and fall times. The infrared vertical cavity surface emitting laser (VCSEL) is exactly one such light source. Fifth generation (5G) systems promise to connect billions of people and trillions of Internet of Things gadgets and sensors at 1 to beyond 20 Gbps via newly auctioned millimeter wave (30 GHz to 300 GHz) spectral bands. By circa 2030 sixth generation (6G) systems envision vast broadband capacity with zero latency â enabling real-time virtual and mixed realities, human-machine interfaces, autonomous vehicles, and much more. The 6G technology adds terahertz wave emitters including infrared VCSELs and VCSEL arrays to vastly increase data rates, boost energy and spectral efficiency, and take advantage of available and unregulated spectral bands. I design, fabricate, and test new experimental VCSEL diodes and novel two-dimensional (2D) VCSEL diode arrays. I study the physics and performance trade-offs of VCSEL light emitters aimed at 5G and 6G optical wireless communication and sensing applications. Via in-house computer modeling and simulation programs, I design VCSEL epitaxial structures â composed of nanometer-thick aluminum-gallium-arsenide, indium-gallium arsenide, and gallium-arsenide-phosphide layers â with peak target emission wavelengths of 940 and 980 nanometers. A commercial foundry grows my experimental VCSEL epitaxial wafers by metal-organic vapor phase epitaxy on 3-inch diameter gallium-arsenide substrates. In my university cleanroom, I fabricate my VCSELs as quarter wafer test pieces using a new VCSEL Array 2018 mask set which contains single VCSELs, and several variations of novel 2D electrically parallel triple (3-element), septuple (7-element), and novemdecuple (19-element) geometric device designs. My fabricated devices feature high frequency, coplanar ground-signal-ground metal contact pads, and top-epitaxial-surface emission. I perform all device tests in my university laser diode laboratory via direct, on-wafer electrical probing under computer control, starting with continuous wave light output power-current-voltage sweeps via a calibrated photodiode-integrating sphere and variable current source. For emission spectra and small-signal frequency response measurements, I collect the emitted VCSEL light with a standard OM1 multiple mode optical fiber (MMF) â connected to either an optical spectrum analyzer or a photoreceiver. For on-wafer data transmission tests across OM1 MMF patch cords, I modulate my VCSELs with nonreturn to zero, pseudorandom bit patterns in the form of 2-level pulse amplitude modulation. I achieve record combinations of optical output power, bandwidth, and efficiency for my large oxide aperture diameter (larger than 20 micrometers) VCSELs and for my VCSEL arrays. For example, I demonstrate 200 milliwatts of optical output power, a bandwidth of 18 GHz, and a wall plug efficiency of 35 percent with a 19-element VCSEL array. I set several records for error free data transmission, for example, 40 Gbps for my triple and septuple VCSEL arrays and 25 Gbps for my novemdecuple VCSEL arrays, well beyond the previous record of 10 Gbps. My work is the first to investigate trade-offs in the highly nontrivial physics of VCSEL arrays aimed at high power and high bandwidth arrays for free space data transmission â producing new guiding principles for further device optimization and product development.ZukĂŒnftige Generationen optischer drahtloser Kommunikations- und Sensorsysteme erfordern kompakte, kostengĂŒnstige, zuverlĂ€ssige und hocheffiziente Lichtquellen, die modulierte Strahlen mit Datenraten von Gigabit pro Sekunde (Gbps) und gepulste Strahlen mit Anstieg- und Abfallzeiten im Sub-Nanosekundenbereich ĂŒber den freien Raum ĂŒbertragen können. Infrarote, oberflĂ€chenemittierende Laser mit vertikaler KavitĂ€t (VCSEL) sind genau eine solche Lichtquelle. Systeme der fĂŒnften Generation (5G) versprechen, Milliarden von Menschen und Billionen von GerĂ€ten und Sensoren fĂŒr das Internet der Dinge mit 1 bis ĂŒber 20 Gbps ĂŒber neu versteigerte Millimeterwellen-SpektralbĂ€nder (30 GHz bis 300 GHz) zu verbinden. Bis etwa 2030 sehen Systeme der sechsten Generation (6G) eine enorme BreitbandkapazitĂ€t ohne Latenzzeit vor â sie ermöglichen virtuelle und gemischte RealitĂ€ten in Echtzeit, Mensch-Maschine-Schnittstellen, autonome Fahrzeuge und vieles mehr. Die 6G-Technologie fĂŒgt Terahertz-Wellensender hinzu, einschlieĂlich Infrarot-VCSELs und VCSEL-Arrays, um die Datenraten signifikant zu erhöhen, die Energie- und Spektraleffizienz zu steigern und die verfĂŒgbaren und noch unregulierten SpektralbĂ€nder zu nutzen. In der vorliegenden Arbeit werden neue experimentelle VCSEL-Dioden und neuartige zweidimensionale (2D) VCSEL-Diodenarrays entworfen, hergestellt und getestet. Die Physik der VCSEL-Lichtemittern, welche auf 5G- und 6G-optische drahtlose Kommunikations- und Sensoranwendungen ausgerichtet sind, wird untersucht und Performance-Tradeoffs fĂŒr die angedachten Anwendungen werden identifiziert und analysiert. Ăber hauseigene Computermodellierungs- und Simulationsprogramme wurden epitaktische VCSEL-Strukturen â bestehend aus nanometerdicken Aluminium-Gallium-Arsenid-, Indium-Gallium-Arsenid- und Gallium-Arsenid-Phosphid-Schichten â mit Peak-ZielemissionswellenlĂ€ngen von 940 und 980 Nanometern entworfen. Ein kommerzieller Hersteller hat die experimentellen VCSEL-Epitaxiewafer durch metallorganische Gasphasenepitaxie auf Gallium-Arsenid-Substraten mit einem Durchmesser von 3 Zoll gewachsen. In einem Reinraum an der UniversitĂ€t wurden die VCSELs als Viertelwafer-TeststĂŒcke mit einem neuen VCSEL Array 2018-Maskensatz gefertigt, der einzelne VCSELs und mehrere Variationen von neuartigen elektrisch parallelen 2D-Tripel- (3-Element), Septuple- (7-Element) und Novemdecuple- (19-Elemente) Strukturdesigns enthĂ€lt. Bei den prozessierten Strukturen handelt es sich um Top-Emitter mit hochfrequenzkompatiblen koplanare Masse-Signal-Masse-Metallkontaktpads. Alle Device-Tests wurden computergesteuert in einem universitĂ€ren Laserdiodenlabor durch direktes elektrisches On-Wafer Probing durchgefĂŒhrt, beginnend mit Dauerstrich-Lichtausgangsleistung-Strom-Spannungs-Sweeps ĂŒber eine kalibrierte Photodioden-Integrationskugel und eine variable Stromquelle. FĂŒr Emissionsspektren und Kleinsignal-Frequenzgangmessungen wurde das emittierte VCSEL-Licht mit einer standardmĂ€Ăigen OM1-Multimode-Glasfaser (MMF) eingesammelt â verbunden mit einem optischen Spektrumanalysator oder einem FotoempfĂ€nger. FĂŒr On-Wafer-DatenĂŒbertragungstests ĂŒber OM1-MMF-Patchkabel wurden die VCSELs mit pseudozufĂ€lligen Bitmustern im Non-Return-To-Zero Format mit 2-Level-Pulsamplitudenmodulation moduliert. In dieser Arbeit werden bisher unerreichte Kombinationen von optischer Ausgangsleistung, Bandbreite und Effizienz fĂŒr VCSEL und VCSEL-Arrays mit groĂer Oxid-Apertur (gröĂer als 20 Mikrometer) demonstriert. Beispielsweise werden 200 Milliwatt optische Ausgangsleistung, eine Bandbreite von 18 GHz und eine Konversionseffizienz elektrischer zu optischer Leistung von 35 Prozent mit einem 19-Element-VCSEL-Array erreicht. Zudem werden mehrere Rekorde fĂŒr fehlerfreie DatenĂŒbertragung aufgestellt, zum Beispiel 40 Gbps fĂŒr Triple- und Septuple-VCSEL-Arrays und 25 Gbps fĂŒr Novemdecuple-VCSEL-Arrays, weit ĂŒber den bisherigen Stand der Technik von 10 Gbps hinaus. Diese Arbeit ist die erste, die Trade-Offs in der hochgradig nichttrivialen Physik von VCSEL-Arrays untersucht, die auf Arrays mit hoher Leistung und hoher Bandbreite fĂŒr die DatenĂŒbertragung im freien Raum abzielen â und damit neue Leitprinzipien fĂŒr die weitere Bauelementoptimierung und Produktentwicklung schafft.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement
Integrated Circuits and Systems for Smart Sensory Applications
Connected intelligent sensing reshapes our society by empowering people with increasing new ways of mutual interactions. As integration technologies keep their scaling roadmap, the horizon of sensory applications is rapidly widening, thanks to myriad light-weight low-power or, in same cases even self-powered, smart devices with high-connectivity capabilities. CMOS integrated circuits technology is the best candidate to supply the required smartness and to pioneer these emerging sensory systems. As a result, new challenges are arising around the design of these integrated circuits and systems for sensory applications in terms of low-power edge computing, power management strategies, low-range wireless communications, integration with sensing devices. In this Special Issue recent advances in application-specific integrated circuits (ASIC) and systems for smart sensory applications in the following five emerging topics: (I) dedicated short-range communications transceivers; (II) digital smart sensors, (III) implantable neural interfaces, (IV) Power Management Strategies in wireless sensor nodes and (V) neuromorphic hardware
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