Semiconductor Power Devices

Transcription

1 Semiconductor Power Devices

2 Josef Lutz Heinrich Schlangenotto Uwe Scheuermann Rik De Doncker Semiconductor Power Devices Physics, Characteristics, Reliability Second Edition 123

3 Josef Lutz Chair Power Electronics and Electromagnetic Compatibility, Faculty of ET/IT Chemnitz University of Technology Chemnitz Germany Heinrich Schlangenotto Neu-Isenburg Germany Uwe Scheuermann Semikron Elektronik GmbH & Co. KG Nuremberg Germany Rik De Doncker Chair Power Generation and Storage Systems, Faculty of ET/IT E.ON ERC, RWTH Aachen University Aachen Germany ISBN ISBN (ebook) Library of Congress Control Number: st edition: Springer-Verlag Berlin Heidelberg nd edition: Springer International Publishing AG 2018 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of 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 transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the 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 this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Printed on acid-free paper This Springer imprint is published by Springer Nature The registered company is Springer International Publishing AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

4 Preface to the Second Edition The first edition of this book was widely used and accepted by professionals in the field. The progress in power devices, however, makes a second edition necessary. For this second edition, the basic chapters on semiconductor properties and pn-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 is considerably augmented. Aspects on 300-mm technology for Si IGBTs were added. New are the sections on radiation-induced doping and on GaN technology. The chapter on Schottky diodes was revised by an improved treatment of the physics of the metal semiconductor junction and extended by sections on Merged Pin Schottky diodes. In the chapter on thyristors, the description of the gate-commutated thyristor GCT is added. The chapter on MOS transistors and field-controlled wide-bandgap devices replaces the former chapter on MOSFETs. Despite the progress in wide-bandgap devices, IGBTs are still seen as the main volume components for future power electronics, new aspects on reverse conducting IGBTs were added, and future potential of the IGBT is discussed. Due to the strong progress in packaging, the former chapter on packaging technology is now replaced by two chapters: Packaging of Power Devices and Reliability and Reliability Testing. Especially the reliability sections are strongly expanded considering new test methods, also in the viewpoint of wide-bandgap devices. A comprehensive section on cosmic ray failures is now placed in this section. Finally, new research results on transient avalanche oscillations were added as well as some aspects on monolithically integrated GaN devices. Several researchers in power devices have supported this work with helpful discussions, suggestions, and comments. These are especially Arnost Kopta and Munaf Rahimo from ABB Semiconductors, Markus Behet from EpiGaN, Richard Reiner from Fraunhofer IAF Freiburg, Daniel Hofmann from Fuji Electric, Thomas Laska, Roland Rupp, Hans-Joachim Schulze, and Ralf Siemieniec from Infineon, Dan Kinzer from Navitas, Marion Junghänel from Semikron, Karl Nesemann from SMA, Tomoyuki Shoji from Toyota Nando Kaminski from University of Bremen, v

5 vi Preface to the Second Edition Ulrich Schwarz from Chemnitz University of Technology, Christian Felgemacher from University of Kassel, and Axel Richter from Baden-Wuerttemberg Cooperative State University. Several Master and Ph.D.students at Chemnitz University of Technology have supported part of the work, especially Menia Beier-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 electronics, which supported this second edition with critical comments and discussions. Chemnitz, Germany Neu-Isenburg, Germany Nuremberg, Germany Aachen, Germany October 2017 Josef Lutz Heinrich Schlangenotto Uwe Scheuermann Rik De Doncker

6 Preface to the First Edition Power electronics is gaining more and more importance in industry and society. It has the potential to substantially increase the efficiency of power systems, a task of great significance. To exploit this potential, not only engineers working in the development of improved and new devices but also application engineers in the field of power electronics need to understand the basic principles of semiconductor power devices. Furthermore, since a semiconductor device can only fulfill its function in a suitable environment, interconnection and packaging technologies with the related material properties have to be considered as well as the problem of cooling, which has to be solved for reliable applications. This book was written for students and for engineers working in the field of power device design and power electronics applications. The focus was set on modern semiconductor switches such as power MOSFETs and IGBTs together with the essential freewheeling diodes. The practicing engineer may start his/her work with the book with the specific power device. Each chapter presents first the device structure and the generic characteristics and then a more thorough discussion is added with the focus on the physical function principles. The in-depth discussions require the principles of semiconductor physics, the functioning of pn-junctions, and the basics of technology. These topics are treated in depth such that the book will also be of value for the semiconductor device specialist. Some subjects are treated in particular detail and presented here for the first time in an English textbook on power devices. In device physics, this is especially the emitter recombination which is used in modern power devices to control forward conduction and switching properties. A detailed discussion of its influence is given using parameters characterizing the emitter recombination properties. Furthermore, because of the growing awareness of the importance of packaging techniques for reliable applications, chapters on packaging and reliability are included. During the development of power electronic systems, engineers often are confronted with failures and unexpected effects with the consequence of time-consuming efforts to isolate the root cause of these effects. Therefore, chapters on failure mechanisms and oscillation effects in power circuits are included in this textbook to supply guidance based on long-time experience. vii

7 viii Preface to the First Edition The book has emerged from lectures on Power devices held by J. Lutz at Chemnitz University of Technology and from earlier lecture notes on Power devices from H. Schlangenotto held at Darmstadt Technical University in Using these lectures and adding considerable material on new devices, packaging, reliability, and failure mechanisms, Lutz published in German the book Halbleiter-Leistungsbauelemente Physik, Eigenschaften, Zuverlässigkeit in The English textbook presented here is far more than a translation; it was considerably extended with new material. The basic chapters on semiconductor properties and pn-junctions and a part of the chapter on pin diodes were revised and enhanced widely by H. Schlangenotto. J. Lutz extended the chapters on thyristors, MOSFETs, IGBTs, and failure mechanisms. U. Scheuermann contributed the chapter on packaging technology, reliability, and system integration. R. De Doncker supplied the introduction 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 helpful discussions, support in translations, suggestions, and comments. These are especially Arnost Kopta, Stefan Linder, and Munaf Rahimo from ABB Semiconductors, Dieter Polenov from BMW, Thomas Laska, Anton Mauder, Franz-Josef Niedernostheide, Ralf Siemieniec, and Gerald Soelkner from Infineon, Martin Domeij 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, Hans Günter Eckel from the University of Rostock. Several diploma and Ph.D. students at Chemnitz University of Technology have supported part of the work, especially Hans-Peter Felsl, Birk Heinze, Roman Baburske, Marco Bohlländer, Tilo Pollera Matthias Baumann, and Thomas Basler. Thomas Plum and Florian Mura from RWTH Aachen have translated the chapter on MOSFETS, and Mary-Joan Blümich has given support with improvements of the English text. Finally, the authors thank many other researchers and students in power electronics, who supported this work with critical comments and discussions. Chemnitz, Germany Neu-Isenburg, Germany Nuremberg, Germany Aachen, Germany March 2010 Josef Lutz Heinrich Schlangenotto Uwe Scheuermann Rik De Doncker

8 Contents 1 Power Semiconductor Devices Key Components for Efficient Electrical Energy Conversion Systems Systems, Power Converters and Power Semiconductor Devices Basic Principles of Power Converters Types of Power Converters and Selection of Power Devices Operating and Selecting Power Semiconductors Applications of Power Semiconductors Power Electronics for Carbon Emission Reduction References Semiconductor Properties Introduction Crystal Structure Energy Gap and Intrinsic Concentration Energy Band Structure and Particle Properties of Carriers The Doped Semiconductor Current Transport Carrier Mobilities and Field Currents High-Field Drift Velocities Diffusion of Carriers, Current Transport Equations and Einstein Relation Recombination Generation and Lifetime of Non-equilibrium Carriers Intrinsic Recombination Mechanisms Recombination at Recombination Centers Including Gold, Platinum and Radiation Defects Impact Ionization ix

9 x Contents 2.9 Basic Equations of Semiconductor Devices Simple Conclusions Temporal and Spatial Decay of a Minority Carrier Concentration Temporal and Spatial Decay of a Charge Density References pn-junctions The pn-junction in Thermal Equilibrium The Abrupt Step Junction Graded Junctions Current-Voltage-Characteristics of the pn-junction Blocking Characteristics and Breakdown of the pn-junction Blocking Current Avalanche Multiplication and Breakdown Voltage Blocking Capability with Wide-Bandgap Semiconductors Injection Efficiency of Emitter Regions Capacitance of pn-junctions References Introduction to Power Device Technology Crystal Growth Neutron Transmutation for Adjustment of the Wafer Doping Epitaxial Growth Diffusion Diffusion Theory, Impurity Distributions Diffusion Constants and Solubility of Dopants High Concentration Effects, Diffusion Mechanisms Ion Implantation Oxidation and Masking Edge Terminations Passivation Recombination Centers Radiation-Induced Doping Some Aspects on Technology of GaN Devices References pin Diodes Structure of the pin Diode I V Characteristic of the pin Diode

10 Contents xi 5.3 Design and Blocking Voltage of the pin Diode Forward Conduction Behavior Carrier Distribution Junction Voltages Voltage Drop Across the Middle Region Voltage Drop in the Hall Approximation Emitter-Recombination, Effective Carrier Lifetime and Forward Characteristic Temperature Dependency of the Forward Characteristics Relation Between Stored Charge and Forward Voltage Turn-on Behavior of Power Diodes Reverse-Recovery of Power Diodes Definitions Reverse-Recovery Related Power Losses Reverse Recovery: Charge Dynamic in the Diode Fast Diodes with Optimized Reverse-Recovery Behavior MOS-Controlled Diodes Outlook References Schottky Diodes Energy Band Diagram of the Metal-Semiconductor Junction Current-Voltage-Characteristics of the Schottky Junction Structure of Schottky Diodes Ohmic Voltage Drop of a Unipolar Device Comparison of Silicon Schottky Diodes and pin Diodes for Rated Voltages of 200 and 100 V Schottky Diodes Based on SiC SiC Unipolar Diode Characteristics Merged Pin Schottky (MPS) Diodes Switching Behavior and Ruggedness of SiC Schottky and MPS Diodes References Bipolar Transistors Function of the Bipolar Transistor Structure of the Bipolar Power Transistor I V Characteristic of the Power Transistor Blocking Behavior of the Bipolar Power Transistor Current Gain of the Bipolar Transistor Base Widening, Field Redistribution and Second Breakdown

11 xii Contents 7.7 Limits of the Silicon Bipolar Transistor SiC Bipolar Transistor References Thyristors Structure and Mode of Function I V Characteristic of the Thyristor Blocking Behavior of the Thyristor The Function of Emitter Shorts Modes to Trigger a Thyristor Trigger Front Spreading Follow-up Triggering and Amplifying Gate Thyristor Turn-off and Recovery Time The Triac The Gate Turn-off Thyristor (GTO) The Gate Commutated Thyristor (GCT) References MOS Transistors and Field Controlled Wide Bandgap Devices Function Principle of the MOSFET Structure of Power MOSFETs Current-Voltage Characteristic of MOS-Transistors Characteristics of the MOSFET Channel The Ohmic Region Compensation Structures in Modern MOSFETs Temperature Dependency of MOSFET Characteristics Switching Properties of the MOSFET Switching Losses of the MOSFET Safe Operating Area of the MOSFET The Inverse Diode of the MOSFET SiC Field Effect Devices SiC JFETs SiC MOSFETs The SiC MOSFET Body Diode GaN Lateral Power Transistors GaN Vertical Power Transistors Outlook References IGBTs Mode of Function The I V Characteristic of the IGBT The Switching Behavior of the IGBT The Basic Types PT-IGBT and NPT-IGBT Plasma Distribution in the IGBT

12 Contents xiii 10.6 Modern IGBTs with Increased Charge Carrier Density Plasma Enhancement by High n-emitter Efficiency The Latch-up Free Cell Geometry The Effect of the Hole Barrier Collector Side Buffer Layers IGBTs with Bidirectional Blocking Capability Reverse Conducting IGBTs The Potential of the IGBT References Packaging of Power Devices The Challenge of Packaging Technology Package Types Capsules The TO-Family and Its Relatives Modules Physical Properties of Materials Thermal Simulation and Thermal Equivalent Circuits Analogy Between Thermal and Electrical Parameters One-Dimensional Equivalent Networks The Three-Dimensional Thermal Network The Transient Thermal Resistance Parasitic Electrical Elements in Power Modules Parasitic Resistances Parasitic Inductances Parasitic Capacities Advanced Packaging Technologies Silver Sintering Technology Diffusion Soldering Advanced Technologies for the Chip Topside Contact Improved Substrates Advanced Packaging Concepts References Reliability and Reliability Testing The Demand for Increasing Reliability High Temperature Reverse Bias Test High Temperature Gate Stress Test Temperature Humidity Bias Test High Temperature and Low Temperature Storage Tests Temperature Cycling and Temperature Shock Test

13 xiv Contents 12.7 Power Cycling Test Power Cycling Test Execution Power Cycling Induced Failure Mechanisms Models for Lifetime Prediction Separation of Failure Modes Mission Profiles and Superposition of Power Cycles Power Cycling Capability of Molded TO Packages Power Cycling of SiC Devices Cosmic Ray Failures The Salt Mine Experiment Origin of Cosmic Rays Cosmic Ray Failure Patterns Basic Failure Mechanism Model Basic Design Rules Extended Model Considering the nn + Junction Further Design Aspects in Extended Models Cosmic Ray Stability of SiC Devices Statistical Evaluation of Reliability Test Results Further Reliability Tests References Destructive Mechanisms in Power Devices Thermal Breakdown Failures by Excess-Temperature Surge Current Overvoltage Voltage Above Blocking Capability Dynamic Avalanche Dynamic Avalanche in Bipolar Devices Dynamic Avalanche in Fast Diodes Diode Structures with High Dynamic Avalanche Capability Turn-off of Over-Current and Dynamic Avalanche in IGBTs Exceeding the Maximum Turn-off Current of GTOs Short-Circuit in IGBTs Short Circuit Types I, II and III Thermal and Electrical Stress in Short Circuit Current Filamentation at Short Circuit Failure Analysis in IGBT Circuits References

14 Contents xv 14 Power Device Induced Oscillations and Electromagnetic Disturbances Frequency Range of Electromagnetic Disturbances LC Oscillations Turn-off Oscillations with IGBTs Connected in Parallel Turn-off Oscillations with Snappy Diodes Turn-off Oscillations with Wide Bandgap Devices Transit-Time Oscillations Plasma-Extraction Transit-Time (PETT) Oscillations Dynamic Impact-Ionization Transit-Time (IMPATT) Oscillations Transient-Avalanche (TA) Oscillations Summarizing Remarks on Transit-Time Oscillations References Integrated Power Electronic Systems Definition and Basic Features Monolithically Integrated Systems Power IC s GaN Monolithic Integrated Systems System Integration on Printed Circuit Board Hybrid Integration References Appendix A: Modeling Parameters of Carrier Mobilities in Si and 4H-SiC Appendix B: Correlates to Recombination Centers Appendix C: Avalanche Multiplication Factors and Effective Ionization Rate Appendix D: Thermal Parameters of Important Materials in Packaging Technology Appendix E: Electric Parameters of Important Materials in Packaging Technology Index

15 Symbols A Area (cm 2 ) B Fulop constant: Proportionality factor for a eff E n c n,p Capture coefficient for electrons/holes (cm 3 s 1 ) c An,p Auger capture coefficient for electrons/holes (cm 3 s 1 ) C Capacitance (As/V) C j Junction capacitance (As/V) D Diffusion constant (cm 2 /s) D A Ambipolar diffusion constant (cm 2 /s) D n,p Diffusion constant of electrons/holes (cm 2 /s) e n,p Emission rate of electrons/holes (s 1 ) E Energy (J, ev) E C Lower edge of the conduction band (ev) E F Fermi-Level (ev) E g Bandgap (ev) E V Upper edge of the valence band (ev) E off Turn-off energy (J) E on Turn-on energy (J) E Electric field strength (V/cm) E c Electric field strength at avalanche breakdown (V/cm) F Statistic distribution function g n,p Therm. generation rate of electrons/holes (cm 3 s 1 ) G n,p Net generation rate of electrons/holes (cm 3 s 1 ) G av Avalanche generation rate (cm 3 s 1 ) h n,p Emitter parameter of n/p emitter (cm 4 s 1 ) i = I(t); current, time dependent (A) I Current (A) I C Collector current (A) I D Drain current (A) I E Emitter current (A) Diode forward current (A) I F xvii

16 xviii Symbols I R I RRM Current in blocking direction (A) Reverse recovery current maximum (A) j Current density (A/cm 2 ) j n,p Current density of electron/hole current (A/cm 2 ) j s Saturation current density (A/cm 2 ) k Boltzmann constant ( ) (J/K) L Inductivity (H) L par Parasitic inductivity (H) L A Ambipolar diffusion length (cm) L D Debye length (cm) L n,p Diffusion length of electrons/holes (cm) n, p Density of free electrons/holes (cm 3 ) n 0, p 0 Density in thermodynamic equilibrium (cm 3 ) n*, p* Density of minority carriers outside therm. equilibrium (cm 3 ) n i Intrinsic carrier density (cm 3 ) n L, p L Density at the left edge of the flooded zone (cm 3 ) n R, p R Density at the right edge of the flooded zone (cm 3 ) n av, p av Density of electrons/holes generated by avalanche (cm 3 ) N A Acceptor density (cm 3 ) N C Effective density of states of the conduction band (cm 3 ) N D Donator density (cm 3 ) N eff Effective doping density N D N A (cm 3 ) N r Density of deep centers (cm 3 ) Nr þ ; Nr Density of positively/negatively charged deep centers (cm 3 ) N V Effective density of states of the valence band (cm 3 ) q Elementary charge ( ) (As) Q Charge (As) Q F Charge carrying the forward current in a bip. device (As) Q RR Measured stored charge of a diode (As) r n,p Therm. recombination rates of electrons/holes (cm 3 s 1 ) R n,p Net recombination rates of electrons/holes (cm 3 s 1 ) R Resistor (Ohm) R off Gate resistance at turn-off (Ohm) R on Gate resistance at turn-on (Ohm) R pr 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) V bat Battery voltage/dc link voltage (V) V B,V BD Avalanche breakdown voltage (V)

17 Symbols xix V C V drift V bi V F V G V FRM V M V R V s V T v n,p v d(n,p) v sat w B Forward voltage of a transistor 1 (V) Voltage drop across an n - -layer (V) Built-in voltage of a pn-junction (V) Forward voltage (diode) (V) Gate voltage (V) Forward recovery voltage peak of a diode (V) Voltage peak (V) Voltage in blocking direction (V) Threshold voltage diode / thyristor / IGBT (V) Threshold voltage channel MOSFET, IGBT (V) Velocity of electrons/holes (cm/s) Drift velocity of electrons/holes (cm/s) Saturation drift velocity at high electric field (cm/s) Width of the n - -layer (cm) w, w SC Width of the space charge layer (cm) x Coordinate (cm) x j Depth of the pn-junction (cm) a Current gain in common-base circuit a T Transport factor a n;p Ionization rates v of electrons/holes (cm 1 ) a eff Effective ionization rate (cm 1 ) b Current gain in common-emitter circuit c Emitter efficiency e 0 Dielectric constant in vacuum ( ) (F/cm) e r Relative dielectric constant (Si: 11.7) l n;p Mobility of free electrons/holes (cm 2 V -1 s -1 ) q Space charge (As/cm 3 ) r Electric conductivity (Acm -1 V -1 ) s n;p s n0;p0 s A;n, s A;p s HL s eff s g s rel U Lifetime of excess eletrons/holes (s) Low-level lifetime of excess electrons/holes (s) Auger lifetime of electrons/holes (s) Carrier lifetime at high injection level (s) Effective carrier lifetime (s) Generation lifetime (s) Relaxation time (s) Ionization integral 1 Remark: In data sheets of manufacturers usually instead of V C the symbol V CE (collector emitter voltage), for V G the acronym V GE (IGBT) or V GS (MOSFET) is used, for V T the symbol V GS(th). Similar symbols are used for the current. The shorter symbols have been chosen in this work.