Semiconductor Power Devices

Josef Lutz • Heinrich SchlangenottoUwe Scheuermann • Rik De Doncker

Semiconductor PowerDevicesPhysics, Characteristics, Reliability

Second Edition

123

Josef LutzChair Power Electronics andElectromagnetic Compatibility, Faculty ofET/IT

Chemnitz University of TechnologyChemnitzGermany

Heinrich SchlangenottoNeu-IsenburgGermany

Uwe ScheuermannSemikron Elektronik GmbH & Co. KGNurembergGermany

Rik De DonckerChair Power Generation and StorageSystems, Faculty of ET/IT

E.ON ERC, RWTH Aachen UniversityAachenGermany

ISBN 978-3-319-70916-1 ISBN 978-3-319-70917-8 (eBook)https://doi.org/10.1007/978-3-319-70917-8

Library of Congress Control Number: 2017958836

1st edition: © Springer-Verlag Berlin Heidelberg 20112nd edition: © Springer International Publishing AG 2018This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or partof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmissionor information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodology now known or hereafter developed.The use of general descriptive names, registered names, trademarks, service marks, etc. in thispublication does not imply, even in the absence of a specific statement, that such names are exempt fromthe relevant protective laws and regulations and therefore free for general use.The publisher, the authors and the editors are safe to assume that the advice and information in thisbook are believed to be true and accurate at the date of publication. Neither the publisher nor theauthors or the editors give a warranty, express or implied, with respect to the material contained herein orfor any errors or omissions that may have been made. The publisher remains neutral with regard tojurisdictional claims in published maps and institutional affiliations.

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Preface to the Second Edition

The first edition of this book was widely used and accepted by professionals in thefield. The progress in power devices, however, makes a second edition necessary.

For this second edition, the basic chapters on semiconductor properties andpn-junctions were revised and extended widely. Effects of doping, current transport,and recombination are now treated much more in detail and depth.

In the chapter on technology, the description of theory of diffusion in silicon isconsiderably augmented. Aspects on 300-mm technology for Si IGBTs were added.New are the sections on radiation-induced doping and on GaN technology. Thechapter on Schottky diodes was revised by an improved treatment of the physicsof the metal–semiconductor junction and extended by sections on Merged PinSchottky diodes. In the chapter on thyristors, the description of thegate-commutated thyristor GCT is added. The chapter on MOS transistors andfield-controlled wide-bandgap devices replaces the former chapter on MOSFETs.Despite the progress in wide-bandgap devices, IGBTs are still seen as the mainvolume components for future power electronics, new aspects on reverse con-ducting IGBTs were added, and future potential of the IGBT is discussed.

Due to the strong progress in packaging, the former chapter on packagingtechnology is now replaced by two chapters: “Packaging of Power Devices” and“Reliability and Reliability Testing.” Especially the reliability sections are stronglyexpanded considering new test methods, also in the viewpoint of wide-bandgapdevices. A comprehensive section on cosmic ray failures is now placed in thissection.

Finally, new research results on transient avalanche oscillations were added aswell as some aspects on monolithically integrated GaN devices.

Several researchers in power devices have supported this work with helpfuldiscussions, suggestions, and comments. These are especially Arnost Kopta andMunaf Rahimo from ABB Semiconductors, Markus Behet from EpiGaN, RichardReiner from Fraunhofer IAF Freiburg, Daniel Hofmann from Fuji Electric, ThomasLaska, Roland Rupp, Hans-Joachim Schulze, and Ralf Siemieniec from Infineon,Dan Kinzer from Navitas, Marion Junghänel from Semikron, Karl Nesemann fromSMA, Tomoyuki Shoji from Toyota Nando Kaminski from University of Bremen,

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Ulrich Schwarz from Chemnitz University of Technology, Christian Felgemacherfrom University of Kassel, and Axel Richter from Baden-WuerttembergCooperative State University. Several Master and Ph.D.students at ChemnitzUniversity of Technology have supported part of the work, especially MeniaBeier-Möbius, Riteshkumar Bhojani, Haiyang Cao, Susanne Fichtner, Jörg Franke,Christian Herold, Shanmuganathan Palanisamy, Peter Seidel, and Guang Zeng.Stefanie Glöckner has given support with improvements of the English text.Finally, the authors thank the many other researchers and students in power elec-tronics, which supported this second edition with critical comments anddiscussions.

Chemnitz, Germany Josef LutzNeu-Isenburg, Germany Heinrich SchlangenottoNuremberg, Germany Uwe ScheuermannAachen, Germany Rik De DonckerOctober 2017

vi Preface to the Second Edition

Preface to the First Edition

Power electronics is gaining more and more importance in industry and society. Ithas the potential to substantially increase the efficiency of power systems, a task ofgreat significance. To exploit this potential, not only engineers working in thedevelopment of improved and new devices but also application engineers in thefield of power electronics need to understand the basic principles of semiconductorpower devices. Furthermore, since a semiconductor device can only fulfill itsfunction in a suitable environment, interconnection and packaging technologieswith the related material properties have to be considered as well as the problem ofcooling, which has to be solved for reliable applications.

This book was written for students and for engineers working in the field ofpower device design and power electronics applications. The focus was set onmodern semiconductor switches such as power MOSFETs and IGBTs together withthe essential freewheeling diodes. The practicing engineer may start his/her workwith the book with the specific power device. Each chapter presents first the devicestructure and the generic characteristics and then a more thorough discussion isadded with the focus on the physical function principles. The in-depth discussionsrequire the principles of semiconductor physics, the functioning of pn-junctions,and the basics of technology. These topics are treated in depth such that the bookwill also be of value for the semiconductor device specialist.

Some subjects are treated in particular detail and presented here for the first timein an English textbook on power devices. In device physics, this is especially theemitter recombination which is used in modern power devices to control forwardconduction and switching properties. A detailed discussion of its influence is givenusing parameters characterizing the emitter recombination properties. Furthermore,because of the growing awareness of the importance of packaging techniques forreliable applications, chapters on packaging and reliability are included. During thedevelopment of power electronic systems, engineers often are confronted withfailures and unexpected effects with the consequence of time-consuming efforts toisolate the root cause of these effects. Therefore, chapters on failure mechanismsand oscillation effects in power circuits are included in this textbook to supplyguidance based on long-time experience.

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The book has emerged from lectures on “Power devices” held by J. Lutz atChemnitz University of Technology and from earlier lecture notes on “Powerdevices” from H. Schlangenotto held at Darmstadt Technical University in 1991–2001. Using these lectures and adding considerable material on new devices,packaging, reliability, and failure mechanisms, Lutz published in German the bookHalbleiter-Leistungsbauelemente – Physik, Eigenschaften, Zuverlässigkeit in 2006.The English textbook presented here is far more than a translation; it was consid-erably extended with new material.

The basic chapters on semiconductor properties and pn-junctions and apart of the chapter on pin diodes were revised and enhanced widely byH. Schlangenotto. J. Lutz extended the chapters on thyristors, MOSFETs, IGBTs,and failure mechanisms. U. Scheuermann contributed the chapter on packagingtechnology, reliability, and system integration. R. De Doncker supplied the intro-duction on power devices as the key components. All the authors have contributed,however, also to other chapters not written mainly by themselves.

Several researchers in power devices have supported this work with helpfuldiscussions, support in translations, suggestions, and comments. These are espe-cially Arnost Kopta, Stefan Linder, and Munaf Rahimo from ABB Semiconductors,Dieter Polenov from BMW, Thomas Laska, Anton Mauder, Franz-JosefNiedernostheide, Ralf Siemieniec, and Gerald Soelkner from Infineon, MartinDomeij and Anders Hallén from KTH Stockholm, Stephane Lefebvre from SATIE,Michael Reschke from Secos, Reinhard Herzer and Werner Tursky from Semikron,Wolfgang Bartsch from SiCED, Dieter Silber from University of Bremen, HansGünter Eckel from the University of Rostock. Several diploma and Ph.D. studentsat Chemnitz University of Technology have supported part of the work, especiallyHans-Peter Felsl, Birk Heinze, Roman Baburske, Marco Bohlländer, Tilo PolleraMatthias Baumann, and Thomas Basler. Thomas Plum and Florian Mura fromRWTH Aachen have translated the chapter on MOSFETS, and Mary-Joan Blümichhas given support with improvements of the English text. Finally, the authors thankmany other researchers and students in power electronics, who supported this workwith critical comments and discussions.

Chemnitz, Germany Josef LutzNeu-Isenburg, Germany Heinrich SchlangenottoNuremberg, Germany Uwe ScheuermannAachen, Germany Rik De DonckerMarch 2010

viii Preface to the First Edition

Contents

1 Power Semiconductor Devices—Key Componentsfor Efficient Electrical Energy Conversion Systems . . . . . . . . . . . . . 11.1 Systems, Power Converters and Power Semiconductor

Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.1 Basic Principles of Power Converters . . . . . . . . . . . . 31.1.2 Types of Power Converters and Selection

of Power Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2 Operating and Selecting Power Semiconductors . . . . . . . . . . . 81.3 Applications of Power Semiconductors . . . . . . . . . . . . . . . . . . 111.4 Power Electronics for Carbon Emission Reduction . . . . . . . . . 14References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2 Semiconductor Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212.2 Crystal Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242.3 Energy Gap and Intrinsic Concentration . . . . . . . . . . . . . . . . . 262.4 Energy Band Structure and Particle Properties of Carriers . . . . 312.5 The Doped Semiconductor . . . . . . . . . . . . . . . . . . . . . . . . . . . 352.6 Current Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

2.6.1 Carrier Mobilities and Field Currents . . . . . . . . . . . . . 452.6.2 High-Field Drift Velocities . . . . . . . . . . . . . . . . . . . . 522.6.3 Diffusion of Carriers, Current Transport

Equations and Einstein Relation . . . . . . . . . . . . . . . . 542.7 Recombination—Generation and Lifetime

of Non-equilibrium Carriers . . . . . . . . . . . . . . . . . . . . . . . . . . 572.7.1 Intrinsic Recombination Mechanisms . . . . . . . . . . . . . 592.7.2 Recombination at Recombination Centers

Including Gold, Platinum and Radiation Defects . . . . . 612.8 Impact Ionization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

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2.9 Basic Equations of Semiconductor Devices . . . . . . . . . . . . . . . 882.10 Simple Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

2.10.1 Temporal and Spatial Decay of a MinorityCarrier Concentration . . . . . . . . . . . . . . . . . . . . . . . . 92

2.10.2 Temporal and Spatial Decay of a Charge Density . . . . 93References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

3 pn-Junctions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013.1 The pn-Junction in Thermal Equilibrium . . . . . . . . . . . . . . . . 101

3.1.1 The Abrupt Step Junction . . . . . . . . . . . . . . . . . . . . . 1043.1.2 Graded Junctions . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

3.2 Current-Voltage-Characteristics of the pn-Junction . . . . . . . . . 1143.3 Blocking Characteristics and Breakdown

of the pn-Junction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1223.3.1 Blocking Current . . . . . . . . . . . . . . . . . . . . . . . . . . . 1223.3.2 Avalanche Multiplication and Breakdown

Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263.3.3 Blocking Capability with Wide-Bandgap

Semiconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353.4 Injection Efficiency of Emitter Regions . . . . . . . . . . . . . . . . . 1373.5 Capacitance of pn-Junctions . . . . . . . . . . . . . . . . . . . . . . . . . . 144References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

4 Introduction to Power Device Technology . . . . . . . . . . . . . . . . . . . . 1494.1 Crystal Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1494.2 Neutron Transmutation for Adjustment

of the Wafer Doping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1514.3 Epitaxial Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1544.4 Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

4.4.1 Diffusion Theory, Impurity Distributions . . . . . . . . . . 1574.4.2 Diffusion Constants and Solubility of Dopants . . . . . . 1654.4.3 High Concentration Effects, Diffusion

Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1684.5 Ion Implantation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1704.6 Oxidation and Masking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1754.7 Edge Terminations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1774.8 Passivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1824.9 Recombination Centers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1834.10 Radiation-Induced Doping . . . . . . . . . . . . . . . . . . . . . . . . . . . 1894.11 Some Aspects on Technology of GaN Devices . . . . . . . . . . . . 191References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

5 pin Diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2015.1 Structure of the pin Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . 2015.2 I–V Characteristic of the pin Diode . . . . . . . . . . . . . . . . . . . . 203

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5.3 Design and Blocking Voltage of the pin Diode . . . . . . . . . . . . 2045.4 Forward Conduction Behavior . . . . . . . . . . . . . . . . . . . . . . . . 210

5.4.1 Carrier Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . 2105.4.2 Junction Voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . 2135.4.3 Voltage Drop Across the Middle Region . . . . . . . . . . 2155.4.4 Voltage Drop in the Hall Approximation . . . . . . . . . . 2165.4.5 Emitter-Recombination, Effective Carrier Lifetime

and Forward Characteristic . . . . . . . . . . . . . . . . . . . . 2185.4.6 Temperature Dependency of the Forward

Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2275.5 Relation Between Stored Charge and Forward Voltage . . . . . . 2285.6 Turn-on Behavior of Power Diodes . . . . . . . . . . . . . . . . . . . . 2305.7 Reverse-Recovery of Power Diodes . . . . . . . . . . . . . . . . . . . . 232

5.7.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2325.7.2 Reverse-Recovery Related Power Losses . . . . . . . . . . 2395.7.3 Reverse Recovery: Charge Dynamic in the Diode . . . 2435.7.4 Fast Diodes with Optimized Reverse-Recovery

Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2515.7.5 MOS-Controlled Diodes . . . . . . . . . . . . . . . . . . . . . . 261

5.8 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

6 Schottky Diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2716.1 Energy Band Diagram of the Metal-Semiconductor

Junction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2716.2 Current-Voltage-Characteristics of the Schottky Junction . . . . . 2736.3 Structure of Schottky Diodes . . . . . . . . . . . . . . . . . . . . . . . . . 2756.4 Ohmic Voltage Drop of a Unipolar Device . . . . . . . . . . . . . . . 276

6.4.1 Comparison of Silicon Schottky Diodes and pinDiodes for Rated Voltages of 200 and 100 V . . . . . . . 280

6.5 Schottky Diodes Based on SiC . . . . . . . . . . . . . . . . . . . . . . . 2806.5.1 SiC Unipolar Diode Characteristics . . . . . . . . . . . . . . 2806.5.2 Merged Pin Schottky (MPS) Diodes . . . . . . . . . . . . . 2856.5.3 Switching Behavior and Ruggedness

of SiC Schottky and MPS Diodes . . . . . . . . . . . . . . . 289References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

7 Bipolar Transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2957.1 Function of the Bipolar Transistor . . . . . . . . . . . . . . . . . . . . . 2957.2 Structure of the Bipolar Power Transistor . . . . . . . . . . . . . . . . 2977.3 I–V Characteristic of the Power Transistor . . . . . . . . . . . . . . . 2977.4 Blocking Behavior of the Bipolar Power Transistor . . . . . . . . . 2997.5 Current Gain of the Bipolar Transistor . . . . . . . . . . . . . . . . . . 3017.6 Base Widening, Field Redistribution

and Second Breakdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

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7.7 Limits of the Silicon Bipolar Transistor . . . . . . . . . . . . . . . . . 3097.8 SiC Bipolar Transistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

8 Thyristors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3138.1 Structure and Mode of Function . . . . . . . . . . . . . . . . . . . . . . . 3138.2 I–V Characteristic of the Thyristor . . . . . . . . . . . . . . . . . . . . . 3178.3 Blocking Behavior of the Thyristor . . . . . . . . . . . . . . . . . . . . 3188.4 The Function of Emitter Shorts . . . . . . . . . . . . . . . . . . . . . . . 3208.5 Modes to Trigger a Thyristor . . . . . . . . . . . . . . . . . . . . . . . . . 3218.6 Trigger Front Spreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3238.7 Follow-up Triggering and Amplifying Gate . . . . . . . . . . . . . . 3248.8 Thyristor Turn-off and Recovery Time . . . . . . . . . . . . . . . . . . 3278.9 The Triac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3298.10 The Gate Turn-off Thyristor (GTO) . . . . . . . . . . . . . . . . . . . . 3308.11 The Gate Commutated Thyristor (GCT) . . . . . . . . . . . . . . . . . 335References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

9 MOS Transistors and Field Controlled Wide Bandgap Devices . . . 3419.1 Function Principle of the MOSFET . . . . . . . . . . . . . . . . . . . . 3419.2 Structure of Power MOSFETs . . . . . . . . . . . . . . . . . . . . . . . . 3439.3 Current-Voltage Characteristic of MOS-Transistors . . . . . . . . . 3469.4 Characteristics of the MOSFET Channel . . . . . . . . . . . . . . . . 3479.5 The Ohmic Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3519.6 Compensation Structures in Modern MOSFETs . . . . . . . . . . . 3539.7 Temperature Dependency of MOSFET Characteristics . . . . . . . 3579.8 Switching Properties of the MOSFET. . . . . . . . . . . . . . . . . . . 3599.9 Switching Losses of the MOSFET . . . . . . . . . . . . . . . . . . . . . 3649.10 Safe Operating Area of the MOSFET . . . . . . . . . . . . . . . . . . . 3659.11 The Inverse Diode of the MOSFET . . . . . . . . . . . . . . . . . . . . 3669.12 SiC Field Effect Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

9.12.1 SiC JFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3719.12.2 SiC MOSFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3749.12.3 The SiC MOSFET Body Diode . . . . . . . . . . . . . . . . . 377

9.13 GaN Lateral Power Transistors . . . . . . . . . . . . . . . . . . . . . . . 3789.14 GaN Vertical Power Transistors . . . . . . . . . . . . . . . . . . . . . . . 3859.15 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

10 IGBTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39110.1 Mode of Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39110.2 The I–V Characteristic of the IGBT . . . . . . . . . . . . . . . . . . . . 39410.3 The Switching Behavior of the IGBT . . . . . . . . . . . . . . . . . . . 39510.4 The Basic Types PT-IGBT and NPT-IGBT . . . . . . . . . . . . . . 39810.5 Plasma Distribution in the IGBT . . . . . . . . . . . . . . . . . . . . . . 402

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10.6 Modern IGBTs with Increased Charge Carrier Density . . . . . . 40410.6.1 Plasma Enhancement by High n-Emitter

Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40410.6.2 The “Latch-up Free Cell Geometry” . . . . . . . . . . . . . 40810.6.3 The Effect of the “Hole Barrier” . . . . . . . . . . . . . . . . 40910.6.4 Collector Side Buffer Layers . . . . . . . . . . . . . . . . . . . 411

10.7 IGBTs with Bidirectional Blocking Capability . . . . . . . . . . . . 41210.8 Reverse Conducting IGBTs . . . . . . . . . . . . . . . . . . . . . . . . . . 41410.9 The Potential of the IGBT . . . . . . . . . . . . . . . . . . . . . . . . . . . 418References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422

11 Packaging of Power Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42711.1 The Challenge of Packaging Technology . . . . . . . . . . . . . . . . 42711.2 Package Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429

11.2.1 Capsules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43011.2.2 The TO-Family and Its Relatives . . . . . . . . . . . . . . . . 43311.2.3 Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

11.3 Physical Properties of Materials . . . . . . . . . . . . . . . . . . . . . . . 44311.4 Thermal Simulation and Thermal Equivalent Circuits . . . . . . . 445

11.4.1 Analogy Between Thermal and ElectricalParameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445

11.4.2 One-Dimensional Equivalent Networks . . . . . . . . . . . 45211.4.3 The Three-Dimensional Thermal Network . . . . . . . . . 45411.4.4 The Transient Thermal Resistance . . . . . . . . . . . . . . . 455

11.5 Parasitic Electrical Elements in Power Modules . . . . . . . . . . . 45811.5.1 Parasitic Resistances . . . . . . . . . . . . . . . . . . . . . . . . . 45911.5.2 Parasitic Inductances . . . . . . . . . . . . . . . . . . . . . . . . . 46211.5.3 Parasitic Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . 466

11.6 Advanced Packaging Technologies . . . . . . . . . . . . . . . . . . . . . 46911.6.1 Silver Sintering Technology . . . . . . . . . . . . . . . . . . . 47011.6.2 Diffusion Soldering . . . . . . . . . . . . . . . . . . . . . . . . . . 47211.6.3 Advanced Technologies for the Chip Topside

Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47511.6.4 Improved Substrates . . . . . . . . . . . . . . . . . . . . . . . . . 47911.6.5 Advanced Packaging Concepts . . . . . . . . . . . . . . . . . 481

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485

12 Reliability and Reliability Testing . . . . . . . . . . . . . . . . . . . . . . . . . . 48912.1 The Demand for Increasing Reliability . . . . . . . . . . . . . . . . . . 48912.2 High Temperature Reverse Bias Test . . . . . . . . . . . . . . . . . . . 49212.3 High Temperature Gate Stress Test . . . . . . . . . . . . . . . . . . . . 49512.4 Temperature Humidity Bias Test . . . . . . . . . . . . . . . . . . . . . . 49912.5 High Temperature and Low Temperature Storage Tests . . . . . . 50212.6 Temperature Cycling and Temperature Shock Test . . . . . . . . . 503

Contents xiii

12.7 Power Cycling Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50512.7.1 Power Cycling Test Execution . . . . . . . . . . . . . . . . . . 50512.7.2 Power Cycling Induced Failure Mechanisms . . . . . . . 51112.7.3 Models for Lifetime Prediction . . . . . . . . . . . . . . . . . 52212.7.4 Separation of Failure Modes . . . . . . . . . . . . . . . . . . . 52612.7.5 Mission Profiles and Superposition

of Power Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53012.7.6 Power Cycling Capability of Molded

TO Packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53412.7.7 Power Cycling of SiC Devices . . . . . . . . . . . . . . . . . 536

12.8 Cosmic Ray Failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54112.8.1 The Salt Mine Experiment . . . . . . . . . . . . . . . . . . . . 54112.8.2 Origin of Cosmic Rays . . . . . . . . . . . . . . . . . . . . . . . 54212.8.3 Cosmic Ray Failure Patterns . . . . . . . . . . . . . . . . . . . 54512.8.4 Basic Failure Mechanism Model . . . . . . . . . . . . . . . . 54712.8.5 Basic Design Rules . . . . . . . . . . . . . . . . . . . . . . . . . . 54812.8.6 Extended Model Considering the nn+ Junction . . . . . . 55312.8.7 Further Design Aspects in Extended Models . . . . . . . 55812.8.8 Cosmic Ray Stability of SiC Devices . . . . . . . . . . . . . 559

12.9 Statistical Evaluation of Reliability Test Results . . . . . . . . . . . 56312.10 Further Reliability Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 576

13 Destructive Mechanisms in Power Devices . . . . . . . . . . . . . . . . . . . 58313.1 Thermal Breakdown—Failures by Excess-Temperature . . . . . . 58313.2 Surge Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58613.3 Overvoltage – Voltage Above Blocking Capability . . . . . . . . . 59013.4 Dynamic Avalanche . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596

13.4.1 Dynamic Avalanche in Bipolar Devices . . . . . . . . . . . 59613.4.2 Dynamic Avalanche in Fast Diodes . . . . . . . . . . . . . . 59813.4.3 Diode Structures with High Dynamic Avalanche

Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60813.4.4 Turn-off of Over-Current and Dynamic Avalanche

in IGBTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61213.5 Exceeding the Maximum Turn-off Current of GTOs . . . . . . . . 61513.6 Short-Circuit in IGBTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616

13.6.1 Short Circuit Types I, II and III . . . . . . . . . . . . . . . . . 61613.6.2 Thermal and Electrical Stress in Short Circuit . . . . . . 62113.6.3 Current Filamentation at Short Circuit . . . . . . . . . . . . 626

13.7 Failure Analysis in IGBT Circuits . . . . . . . . . . . . . . . . . . . . . 630References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633

xiv Contents

14 Power Device Induced Oscillations and ElectromagneticDisturbances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63714.1 Frequency Range of Electromagnetic Disturbances . . . . . . . . . 63714.2 LC Oscillations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

14.2.1 Turn-off Oscillations with IGBTs Connectedin Parallel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

14.2.2 Turn-off Oscillations with Snappy Diodes . . . . . . . . . 64214.2.3 Turn-off Oscillations with Wide Bandgap

Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64514.3 Transit-Time Oscillations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647

14.3.1 Plasma-Extraction Transit-Time (PETT)Oscillations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648

14.3.2 Dynamic Impact-Ionization Transit-Time(IMPATT) Oscillations . . . . . . . . . . . . . . . . . . . . . . . 655

14.3.3 Transient-Avalanche (TA) Oscillations . . . . . . . . . . . . 65914.3.4 Summarizing Remarks on Transit-Time

Oscillations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664

15 Integrated Power Electronic Systems . . . . . . . . . . . . . . . . . . . . . . . 66715.1 Definition and Basic Features . . . . . . . . . . . . . . . . . . . . . . . . 66715.2 Monolithically Integrated Systems – Power IC’s . . . . . . . . . . . 67015.3 GaN Monolithic Integrated Systems . . . . . . . . . . . . . . . . . . . . 67315.4 System Integration on Printed Circuit Board . . . . . . . . . . . . . . 67615.5 Hybrid Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 679References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685

Appendix A: Modeling Parameters of Carrier Mobilities in Siand 4H-SiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 689

Appendix B: Correlates to Recombination Centers . . . . . . . . . . . . . . . . . 691

Appendix C: Avalanche Multiplication Factors and EffectiveIonization Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697

Appendix D: Thermal Parameters of Important Materialsin Packaging Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . 703

Appendix E: Electric Parameters of Important Materialsin Packaging Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . 705

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 707

Contents xv

Symbols

A Area (cm2)B Fulop constant: Proportionality factor for aeff �En

cn,p Capture coefficient for electrons/holes (cm3s−1)cAn,p Auger capture coefficient for electrons/holes (cm3s−1)C Capacitance (As/V)Cj Junction capacitance (As/V)D Diffusion constant (cm2/s)DA Ambipolar diffusion constant (cm2/s)Dn,p Diffusion constant of electrons/holes (cm2/s)en,p Emission rate of electrons/holes (s−1)E Energy (J, eV)EC Lower edge of the conduction band (eV)EF Fermi-Level (eV)Eg Bandgap (eV)EV Upper edge of the valence band (eV)Eoff Turn-off energy (J)Eon Turn-on energy (J)E Electric field strength (V/cm)Ec Electric field strength at avalanche breakdown (V/cm)F Statistic distribution functiongn,p Therm. generation rate of electrons/holes (cm−3s−1)Gn,p Net generation rate of electrons/holes (cm−3s−1)Gav Avalanche generation rate (cm−3s−1)hn,p Emitter parameter of n/p emitter (cm4s−1)i = I(t); current, time dependent (A)I Current (A)IC Collector current (A)ID Drain current (A)IE Emitter current (A)IF Diode forward current (A)

xvii

IR Current in blocking direction (A)IRRM Reverse recovery current maximum (A)j Current density (A/cm2)jn,p Current density of electron/hole current (A/cm2)js Saturation current density (A/cm2)k Boltzmann constant (1.38066 � 10−23) (J/K)L Inductivity (H)Lpar Parasitic inductivity (H)LA Ambipolar diffusion length (cm)LD Debye length (cm)Ln,p Diffusion length of electrons/holes (cm)n, p Density of free electrons/holes (cm−3)n0, p0 Density in thermodynamic equilibrium (cm−3)n*, p* Density of minority carriers outside therm. equilibrium (cm−3)ni Intrinsic carrier density (cm−3)nL, pL Density at the left edge of the flooded zone (cm−3)nR, pR Density at the right edge of the flooded zone (cm−3)nav, pav Density of electrons/holes generated by avalanche (cm−3)NA Acceptor density (cm−3)NC Effective density of states of the conduction band (cm−3)ND Donator density (cm−3)Neff Effective doping density |ND – NA| (cm

−3)Nr Density of deep centers (cm−3)N þr ; N�

r Density of positively/negatively charged deep centers (cm−3)NV Effective density of states of the valence band (cm−3)q Elementary charge (1.60218 � 10−19) (As)Q Charge (As)QF Charge carrying the forward current in a bip. device (As)QRR Measured stored charge of a diode (As)rn,p Therm. recombination rates of electrons/holes (cm−3s−1)Rn,p Net recombination rates of electrons/holes (cm−3s−1)R Resistor (Ohm)Roff Gate resistance at turn-off (Ohm)Ron Gate resistance at turn-on (Ohm)Rpr Projected range (cm)Rth Thermal resistance (K/W)s Soft factor of a diode (–)S Particles per area (cm−2)t Time (s)T Temperature (°C, K)v = V(t); voltage, time dependent (V)V Voltage (V)Vbat Battery voltage/DC link voltage (V)VB,VBD Avalanche breakdown voltage (V)

xviii Symbols

VC Forward voltage of a transistor1 (V)Vdrift Voltage drop across an n--layer (V)Vbi Built-in voltage of a pn-junction (V)VF Forward voltage (diode) (V)VG Gate voltage (V)VFRM Forward recovery voltage peak of a diode (V)VM Voltage peak (V)VR Voltage in blocking direction (V)Vs Threshold voltage diode / thyristor / IGBT (V)VT Threshold voltage channel MOSFET, IGBT (V)vn,p Velocity of electrons/holes (cm/s)vd(n,p) Drift velocity of electrons/holes (cm/s)vsat Saturation drift velocity at high electric field (cm/s)wB Width of the n--layer (cm)w, wSC Width of the space charge layer (cm)x Coordinate (cm)xj Depth of the pn-junction (cm)a Current gain in common-base circuitaT Transport factoran;p Ionization rates v of electrons/holes (cm−1)aeff Effective ionization rate (cm−1)b Current gain in common-emitter circuitc Emitter efficiencye0 Dielectric constant in vacuum (8.85418 � 10−14) (F/cm)er Relative dielectric constant (Si: 11.7)ln;p Mobility of free electrons/holes (cm2V-1s-1)q Space charge (As/cm3)r Electric conductivity (Acm-1V-1)sn;p Lifetime of excess eletrons/holes (s)sn0;p0 Low-level lifetime of excess electrons/holes (s)sA;n, sA;p Auger lifetime of electrons/holes (s)sHL Carrier lifetime at high injection level (s)seff Effective carrier lifetime (s)sg Generation lifetime (s)srel Relaxation time (s)U Ionization integral

1Remark: In data sheets of manufacturers usually instead of VC the symbol VCE (collector–emitter–voltage), for VG the acronym VGE (IGBT) or VGS (MOSFET) is used, for VT the symbolVGS(th). Similar symbols are used for the current. The shorter symbols have been chosen in thiswork.

Symbols xix