High-Performance Packaging Technology for Wide Bandgap Semiconductor Modules

The properties of wide band gap (WBG) semiconductors are beneficial to power electronics applications ranging from consumer electronics and renewable energy to electric vehicles and high-power traction applications like high-speed trains. WBG devices, properly integrated, will allow power electronics systems to be smaller, lighter, operate at higher temperatures, and at higher frequencies than previous generations of Si-based systems. These will contribute to higher efficiency, and therefore, lower lifecycle costs and lower CO2 emissions. Over 20 years have been spent developing WBG materials, low-defect-density wafers, epitaxy, and device fabrication and processing technology. In power electronics applications, devices are normally packaged into large integrated modules with electrical, mechanical and thermal connection to the system and control circuit. The first generations of WBG device have used conventional or existing module designs to allow drop-in replacement of Si devices; this approach limits the potential benefit. To realize the full potential of WBG devices, especially the higher operating temperatures and faster switching frequency, a new generation of packaging design and technology concepts must be widely implemented

Methods and Results of Power Cycling Tests for Semiconductor Power Devices

This work intends to enhance the state of the research in power cycling tests with statements on achievable measurement accuracy, proposed test bench topologies and recommendations on improved test strategies for various types of semiconductor power devices. Chapters 1 and 2 describe the current state of the power cycling tests in the context of design for reliability comprising applicable standards and lifetime models. Measurement methods in power cycling tests for the essential physical parameters are explained in chapter 3. The dynamic and static measurement accuracy of voltage, current and temperature are discussed. The feasibly achievable measurement delay tmd of the maximal junction temperature Tjmax, its consequences on accuracy and methods to extrapolate to the time point of the turn-off event are explained. A method to characterize the thermal path of devices to the heatsink via measurements of the thermal impedance Zth is explained. Test bench topologies starting from standard setups, single to multi leg DC benches are discussed in chapter 4. Three application-closer setups implemented by the author are explained. For tests on thyristors a test concept with truncated sinusoidal current waveforms and online temperature measurement is introduced. An inverter-like topology with actively switching IGBTs is presented. In contrast to standard setups, there the devices under test prove switching capability until reaching the end-of-life criteria. Finally, a high frequency switching topology with low DC-link voltage and switching losses contributing significantly to the overall power losses is presented providing new degrees of freedom for setting test conditions. The particularities of semiconductor power devices in power cycling tests are thematized in chapter 5. The first part describes standard packages and addressed failure mechanisms in power cycling. For all relevant power electronic devices in silicon and silicon carbide, the devices’ characteristics, methods for power cycling and their consequences for test results are explained. The work is concluded and suggestions for future work are given in chapter 6.:Abstract 1 Kurzfassung 3 Acknowledgements 5 Nomenclature 10 Abbreviations 10 Symbols 12 1 Introduction 19 2 Applicable Standards and Lifetime Models 25 3 Measurement parameters in power cycling tests 53 4 Test Bench Topologies 121 5 Semiconductor Power Devices in Power Cycling 158 6 Conclusion and Outlook 229 References 235 List of Publications 253 Theses 257Diese Arbeit bereichert den Stand der Wissenschaft auf dem Gebiet von Lastwechseltests mit Beiträgen zu verbesserter Messgenauigkeit, vorgeschlagenen Teststandstopologien und verbesserten Teststrategien für verschiedene Arten von leistungselektronischen Bauelementen. Kurzgefasst der Methodik von Lastwechseltests. Das erste Themengebiet in Kapitel 1 und Kapitel 2 beschreibt den aktuellen Stand zu Lastwechseltests im Kontext von Design für Zuverlässigkeit, welcher in anzuwendenden Standards und publizierten Lebensdauermodellen dokumentiert ist. Messmethoden für relevante physikalische Parameter in Lastwechseltests sind in Kapitel 3. erläutert. Zunächst werden dynamische und statische Messgenauigkeit für Spannung, Strom und Temperaturen diskutiert. Die tatsächlich erreichbare Messverzögerung tMD der maximalen Sperrschichttemperatur Tjmax und deren Auswirkung auf die Messgenauigkeit der Lastwechselfestigkeit wird dargelegt. Danach werden Methoden zur Rückextrapolation zum Zeitpunkt des Abschaltvorgangs des Laststroms diskutiert. Schließlich wird die Charakterisierung des Wärmepfads vom Bauelement zur Wärmesenke mittels Messung der thermischen Impedanz Zth behandelt. In Kapitel 4 werden Teststandstopologien beginnend mit standardmäßig genutzten ein- und mehrsträngigen DC-Testständen vorgestellt. Drei vom Autor umgesetzte anwendungsnahe Topologien werden erklärt. Für Tests mit Thyristoren wird ein Testkonzept mit angeschnittenem sinusförmigem Strom und in situ Messung der Sperrschichttemperatur eingeführt. Eine umrichterähnliche Topologie mit aktiv schaltenden IGBTs wird vorgestellt. Zuletzt wird eine Topologie mit hoch frequent schaltenden Prüflingen an niedriger Gleichspannung bei der Schaltverluste signifikant zur Erwärmung der Prüflinge beitragen vorgestellt. Dies ermöglicht neue Freiheitsgrade um Testbedingungen zu wählen. Die Besonderheiten von leistungselektronischen Bauelementen werden in Kapitel 5 thematisiert. Der erste Teil beschreibt Gehäusetypen und adressierte Fehlermechanismen in Lastwechseltests. Für alle untersuchten Bauelementtypen in Silizium und Siliziumkarbid werden Charakteristiken, empfohlene Methoden für Lastwechseltests und Einflüsse auf Testergebnisse erklärt. Die Arbeit wird in Kapitel 6 zusammengefasst und Vorschläge zu künftigen Arbeiten werden unterbreitet.:Abstract 1 Kurzfassung 3 Acknowledgements 5 Nomenclature 10 Abbreviations 10 Symbols 12 1 Introduction 19 2 Applicable Standards and Lifetime Models 25 3 Measurement parameters in power cycling tests 53 4 Test Bench Topologies 121 5 Semiconductor Power Devices in Power Cycling 158 6 Conclusion and Outlook 229 References 235 List of Publications 253 Theses 25

Infrastructure for washable computing

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 1999.Includes bibliographical references (leaves 73-74).Wash-and-wear multilayer electronic circuitry can be constructed on fabric substrates, using conductive textiles and suitably packaged components. Fabrics are perhaps the first composite materials engineered by humanity; their evolution led to the development of the Jacquard loom, which itself led to the development of the modern computer. The development of fabric circuitry is a compelling closure of the cycle that points to a new class of textiles which interact with their users and their environments, while retaining the properties that made them the first ubiquitous "smart material". Fabrics are in several respects superior to existing flexible substrates in terms of their durability, conformability, and breathability. The present work adopts a modular approach to circuit fabrication, from which follow circuit design techniques and component packages optimized for use in fabric-based circuitry, flexible all-fabric interconnects, and multilayer circuits. While maintaining close compatibility with existing components, tools, and techniques, the present work demonstrates all steps of a process to create multilayer printed circuits on fabric substrates using conductive textiles.by E. Rehmi Post.S.M

NASA Tech Briefs Index 1980

Tech Briefs are short announcements of new technology derived from the research and development activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This Index to NASA Tech Briefs contains abstracts and four indexes -- subject,. personal author, originating Center, and Tech Brief number -- for 1980 Tech Briefs

Fabrication and High Speed Optoelectronic Characterization of Semiconductor Devices

This work is an investigation on the use of high speed optoelectronic techniques for the characterization of semiconductor devices. A low-frequency electrooptic probe station was demonstrated as well as the optoelectronic sampling scheme. The optoelectronic sampling technique relies on fast photoconductive switches for its operation. The autocorrelation signal detected in optoelectronic sampling was compared with signal detection by conventional techniques employing a sampling oscilloscope and a network analyser. The optoelectronic techniques described in this work depend critically on short-pulse lasers for the measurement of high speed devices. A fibre-grating pulse compressor was set-up to shorten the 120 ps pulses produced by a mode-locked Nd:YAG laser. Compression by a factor of 40 was demonstrated and nearly transform limited pulses of 3 ps duration were obtained. However, the output of the pulse compressor is very noisy and the output power is not high enough to enable electrooptic sampling experiments, in a jitter-free scheme. The same Nd:YAG laser was frequency doubled and used to synchronously pump a rhodamine 6G dye laser. Autocorrelation measurements obtained with the dye laser are again, very noisy and with poor reproducibility. The noise problems with the pulse compressor and with the dye laser were traced back to the Nd:YAG pump laser. It is concluded that this laser should be avoided as the source of short pulses for the electrooptic and optoelectronic measurement techniques. The use of a feedback loop is likely to reduce the noise in this laser, but drift in the intensity in a long time scale would still be present. A mode-locked Ti:Sapphire laser was also used for measurements in this project. Autocorrelation measurements taken with this laser are totally reproducible and contain little or no noise. The devices measured in this project were made by a combination of electron-beam lithography and photolithography. The use of these two lithography techniques together was made possible by the design of a mask set with alignment marks which can be used for registration in a mask aligner and in the electron beam lithography machine. Discrete devices were made and characterized by electrical techniques. Fabrication procedures were developed for resistors, Metal-Insulator-Metal (MIM) capacitors and for the Optoelecttonic Sampling Device (OSD). Discrete Mesfets were fabricated on MBE grown epilayers and their I-V characteristics were measured. A simplified optoelectronic sampling device was designed and made in a single lithographic step. It provides a quick way of producing devices in which autocorrelation measurements can be performed to determine the carrier lifetime in the substrate material. The optoelectronic sampling devices were made on four different substrate materials. The first one is a high purity, MBE grown GaAs epilayer, with very long lifetime (2ns). The control samples were made on "standard" semi-insulating GaAs, whose carrier lifetime is ~200 ps. Proton implantation in some of these devices made on SI GaAs substrate was used as a means of shortening the carrier lifetime, to produce fast turn-off times in the photoconductive switches. The lifetime after implantation of 4 x 10e14 protons/cm2 was estimated from an optoelectronic sampling measurement, to be around 40 ps. This is still a very long lifetime for the photoconductive switches. It is thought that self-annealing of the deep electron traps, caused by the lack of temperature control in the implanter, prevented the achievement of short lifetime in the switches. GaAs epilayers were grown by MBE at a temperature around 25

Gate oxide failure in MOS devices

The thesis presents an experimental and theoretical investigation of gate oxide breakdown in MOS networks, with a particular emphasis on constant voltage overstress failure. It begins with a literature search on gate oxide failure mechanisms, particularly time-dependent dielectric breakdown, in MOS devices. The experimental procedure is then reported for the study of gate oxide breakdown under constant voltage stress. The experiments were carried out on MOSFETs and MOS capacitor structures, recording the characteristics of the devices before and after the stress. The effects of gate oxide breakdown in one of the transistors in an nMOS inverter were investigated and several parameters were found to have changed. A mathematical model for oxide breakdown, based on physical mechanisms, is proposed. Both electron and hole trapping occurred during the constant voltage stress. Breakdown appears to take place when the trapped hole density reach a critical value. PSPICE simulations were performed for the MOSFETs, nMOS inverter and CMOS logic circuits. Two models of MOSFET with gate oxide short were validated. A good agreement between experiments and simulations was achieved

Flip chip attachment methods : a methodology for evaluating the effects of supplier process variation and supplier relationships on product reliability

Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management; and, Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.Includes bibliographical references (p. 109-110).by Sherry L. Clough.M.S

The role of power device technology in the electric vehicle powertrain

In the automotive industry, the design and implementation of power converters and especially inverters, are at a turning point. Silicon (Si) IGBTs are at present the most widely used power semiconductors in most commercial vehicles. However, this trend is beginning to change with the appearance of wide-bandgap (WBG) devices, particularly silicon carbide (SiC) and gallium nitride (GaN). It is therefore advisable to review their main features and advantages, to update the degree of their market penetration, and to identify the most commonly used alternatives in automotive inverters. In this paper, the aim is therefore to summarize the most relevant characteristics of power inverters, reviewing and providing a global overview of the most outstanding aspects (packages, semiconductor internal structure, stack-ups, thermal considerations, etc.) of Si, SiC, and GaN power semiconductor technologies, and the degree of their use in electric vehicle powertrains. In addition, the paper also points out the trends that semiconductor technology and next-generation inverters will be likely to follow, especially when future prospects point to the use of “800 V" battery systems and increased switching frequencies. The internal structure and the characteristics of the power modules are disaggregated, highlighting their thermal and electrical characteristics. In addition, aspects relating to reliability are considered, at both the discrete device and power module level, as well as more general issues that involve the entire propulsion system, such as common-mode voltage.This work has been supported in part by the Government of the Basque Country through the fund for research groups of the Basque University System IT1440-22 and the Ministerio de Ciencia e Innovación of Spain as part of project PID2020-115126RB-I00 and FEDER funds. Finally, the collaboration of Yole Développement (Yole) is appreciated for providing updated data on its resources