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On Reliability of SiC Power Devices in Power Electronics
KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.ORCID iD: 0000-0003-0570-9599
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Silicon Carbide (SiC) is a wide-bandgap (WBG) semiconductor materialwhich has several advantages such as higher maximum electric field, lowerON-state resistance, higher switching speeds, and higher maximum allowablejunction operation temperature compared to Silicon (Si). In the 1.2 kV - 1.7kV voltage range, power devices in SiC are foreseen to replace Si Insulatedgatebipolar transistors (IGBTs) for applications targeting high efficiency,high operation temperatures and/or volume reductions. In particular, theSiC Metal-oxide semiconductor field-effect transistor (MOSFET) – which isvoltage controlled and normally-OFF – is the device of choice due to the easeof its implementation in designs using Si IGBTs.In this work the reliability of SiC devices, in particular that of the SiCMOSFET, has been investigated. First, the possibility of paralleling two discreteSiC MOSFETs is investigated and validated through static and dynamictests. Parallel-connection was found to be unproblematic. Secondly, drifts ofthe threshold voltage and forward voltage of the body diode of the SiC MOSFETare investigated through long-term tests. Also these reliability aspectswere found to be unproblematic. Thirdly, the impact of the package on thechip reliability is discussed through a modeling of the parasitic inductancesof a standard module and the impact of those inductances on the gate oxide.The model shows imbalances in stray inductances and parasitic elementsthat are problematic for high-speed switching. A long-term test on the impactof humidity on junction terminations of SiC MOSFETs dies and SiCSchottky dies encapsulated in the same standard package reveals early degradationfor some modules situated outdoors. Then, the short-circuit behaviorof three different types (bipolar junction transistor, junction field-effect transistor,and MOSFET) of 1.2 kV SiC switching devices is investigated throughexperiments and simulations. The necessity to turn OFF the device quicklyduring a fault is supported with a detailed electro-thermal analysis for eachdevice. Design guidelines towards a rugged and fast short-circuit protectionare derived. For each device, a short-circuit protection driver was designed,built and validated experimentally. The possibility of designing diode-lessconverters with SiC MOSFETs is investigated with focus on surge currenttests through the body diode. The discovered fault mechanism is the triggeringof the npn parasitic bipolar transistor. Finally, a life-cycle cost analysis(LCCA) has been performed revealing that the introduction of SiC MOSFETsin already existing IGBT designs is economically interesting. In fact,the initial investment is saved later on due to a higher efficiency. Moreover,the reliability is improved, which is beneficial from a risk-management pointof-view. The total investment over 20 years is approximately 30 % lower fora converter with SiC MOSFETs although the initial converter cost is 30 %higher.

Abstract [sv]

Kiselkarbid (SiC) är ett bredbandgapsmaterial (WBG) som har flera fördelar,såsom högre maximal elektrisk fältstyrka, lägre ON-state resitans, högreswitch-hastighet och högre maximalt tillåten arbetstemperatur jämförtmed kisel (Si). I spänningsområdet 1,2-1,7 kV förutses att effekthalvledarkomponenteri SiC kommer att ersätta Si Insulated-gate bipolar transistorer(IGBT:er) i tillämpningar där hög verkningsgrad, hög arbetstemperatur ellervolymreduktioner eftersträvas. Förstahandsvalet är en SiC Metal-oxidesemiconductor field-effect transistor (MOSFET) som är spänningsstyrd ochnormally-OFF, egenskaper som möjliggör enkel implementering i konstruktionersom använder Si IGBTer.I detta arbete undersöks tillförlitligheten av SiC komponenter, specielltSiC MOSFET:en. Först undersöks möjligheten att parallellkoppla tvådiskretaSiC MOSFET:ar genom statiska och dynamiska prov. Parallellkopplingbefanns vara oproblematisk. Sedan undersöks drift av tröskelspänning ochbody-diodens framspänning genom långtidsprov. Ocksådessa tillförlitlighetsaspekterbefanns vara oproblematiska. Därefter undersöks kapslingens inverkanpåchip:et genom modellering av parasitiska induktanser hos en standardmoduloch inverkan av dessa induktanser pågate-oxiden. Modellen påvisaren obalans mellan de parasitiska induktanserna, något som kan varaproblematiskt för snabb switchning. Ett långtidstest av inverkan från fuktpåkant-termineringar för SiC-MOSFET:ar och SiC-Schottky-dioder i sammastandardmodul avslöjar tidiga tecken pådegradering för vissa moduler somvarit utomhus. Därefter undersöks kortslutningsbeteende för tre typer (bipolärtransistor,junction-field-effect transistor och MOSFET) av 1.2 kV effekthalvledarswitchargenom experiment och simuleringar. Behovet att stänga avkomponenten snabbt stöds av detaljerade elektrotermiska simuleringar för allatre komponenter. Konstruktionsriktlinjer för ett robust och snabbt kortslutningsskyddtas fram. För var och en av komponenterna byggs en drivkrets medkortslutningsskydd som valideras experimentellt. Möjligheten att konstrueradiodlösa omvandlare med SiC MOSFET:ar undersöks med fokus påstötströmmargenom body-dioden. Den upptäckta felmekanismen är ett oönskat tillslagav den parasitiska npn-transistorn. Slutligen utförs en livscykelanalys(LCCA) som avslöjar att introduktionen av SiC MOSFET:ar i existerandeIGBT-konstruktioner är ekonomiskt intressant. Den initiala investeringensparas in senare pågrund av en högre verkningsgrad. Dessutom förbättrastillförlitligheten, vilket är fördelaktigt ur ett riskhanteringsperspektiv. Dentotala investeringen över 20 år är ungefär 30 % lägre för en omvandlare medSiC MOSFET:ar även om initialkostnaden är 30 % högre.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , 215 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2017:038
Keyword [en]
Silicon Carbide, Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), Junction Field-Effect Transistor(JFET), Bipolar Junction Transistor (BJT), Reliability, Failure Analysis, Reliability Testing, Short- Circuit Currents, Humidity, Resonant converter, Series-resonant converter (SLR), Base drive circuits, Gate drive circuits, Life-Cycle Cost Analysis (LCCA)
Keyword [sv]
Kiselkarbid, MOSFETar, JFETar, Bipolär Junction Transistor (BJT), Tillförlitlighet, Robusthet, Felanalys, Tillförlitlighetstestning, Kortslutningsströmmar, Luftfuktighet, Resonansomvandlare, Serie-resonansomvandlare (SLR), Basdrivkretsar, Gate-drivkretsar, Felskydd, Livscykelkostnadsanalys
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-207763ISBN: 978-91-7729-445-0 (print)OAI: oai:DiVA.org:kth-207763DiVA: diva2:1098077
Public defence
2017-06-15, Kollegiesalen, Brinellvägen 8, KTH-huset, våningsplan 4, KTH Campus, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

QC 20170524

Available from: 2017-05-24 Created: 2017-05-23 Last updated: 2017-05-24Bibliographically approved
List of papers
1. Experimental investigations of static and transient current sharing of parallel-connected silicon carbide MOSFETs
Open this publication in new window or tab >>Experimental investigations of static and transient current sharing of parallel-connected silicon carbide MOSFETs
Show others...
2013 (English)In: 2013 15th European Conference on Power Electronics and Applications, EPE 2013, 2013Conference paper (Refereed)
Abstract [en]

An Experimental performance analysis of a parallel connection of two 1200/80 MΩ silicon carbide SiC MOSFETs is presented. Static parallel connection was found to be unproblematic. The switching performance of several pairs of parallel-connected MOSFETs is shown employing a common simple totem-pole driver. Good transient current sharing and high-speed switching waveforms with small oscillations are presented. To conclude this analysis, a dc/dc boost converter using parallel-connected SiC MOSFETs is designed for stepping up a voltage from 50 V to 560 V. It has been found that at high frequencies, a mismatch in switching losses results in thermal unbalance between the devices.

Series
2013 15th European Conference on Power Electronics and Applications, EPE 2013
Keyword
MOS device, MOSFET, Parallel operation, Silicon Carbide (SiC), Switching losses
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-139155 (URN)10.1109/EPE.2013.6634432 (DOI)2-s2.0-84890162416 (Scopus ID)9781479901166 (ISBN)
Conference
2013 15th European Conference on Power Electronics and Applications, EPE 2013; Lille, France, 2-6 September 2013
Note

QC 20140108

Available from: 2014-01-08 Created: 2014-01-07 Last updated: 2017-05-29Bibliographically approved
2. Analysis of Parasitic Elements of SiC Power Modules With Special Emphasis on Reliability Issues
Open this publication in new window or tab >>Analysis of Parasitic Elements of SiC Power Modules With Special Emphasis on Reliability Issues
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2016 (English)In: IEEE Journal of Emerging and Selected Topics in Power Electronics, ISSN 2168-6777, E-ISSN 2168-6785, Vol. 4, no 3, 988-995 p.Article in journal (Refereed) Published
Abstract [en]

Commercially available silicon carbide (SiC) MOSFET power modules often have a design based on existing packages previously used for silicon insulated-gate bipolar transistors. However, these packages are not optimized to take advantage of the SiC benefits, such as high switching speeds and high-temperature operation. The package of a half-bridge SiC MOSFET module has been modeled and the parasitic elements have been extracted. The model is validated through experiments. An analysis of the impact of these parasitic elements on the gate-source voltage on the chip has been performed for both low switching speeds and high switching speeds. These results reveal potential reliability issues for the gate oxide if higher switching speeds are targeted.

Place, publisher, year, edition, pages
IEEE, 2016
Keyword
Multichip modules, packaging, power MOSFETs, reliability, silicon carbide (SiC)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-192713 (URN)10.1109/JESTPE.2016.2585666 (DOI)000381441600030 ()2-s2.0-84982786778 (Scopus ID)
Conference
1st Annual IEEE Workshop on Wide Bandgap Power Devices and Applications (WiPDA), OCT 27-29, 2013, Ohio State Univ, Columbus, OH
Note

QC 20160926

Available from: 2016-09-26 Created: 2016-09-20 Last updated: 2017-05-29Bibliographically approved
3. Investigation of long-term parameter variations of SiC power MOSFETs
Open this publication in new window or tab >>Investigation of long-term parameter variations of SiC power MOSFETs
2015 (English)In: Power Electronics and Applications (EPE’15 ECCE-Europe), 2015 17th European Conference on, IEEE , 2015, 1-10 p.Conference paper, Published paper (Refereed)
Abstract [en]

Experimental investigations on the gate-oxide and body-diode reliability of commercially available Silicon Carbide (SiC) MOSFETs from the second generation are performed. The body-diode conduction test is performed with a current density of 50 A/cm2 in order to determine if the body-diode of the MOSFETs is free from bipolar degradation. The second test is stressing the gate-oxide. A negative bias is applied on the gate oxide in order to detect and quantify potential drifts.

Place, publisher, year, edition, pages
IEEE, 2015
Keyword
circuit reliability;elemental semiconductors;logic gates;power MOSFET;bipolar degradation;body-diode conduction test;body-diode reliability;gate-oxide reliability;long-term parameter variations;negative bias;potential drift detection;potential drift quantification;silicon carbide power MOSFET;Logic gates;MOSFET;Reliability;Silicon carbide;Stress;Temperature measurement;Threshold voltage;Device characterization;MOSFET;Power semiconductor device;Reliability;Robustness;Silicon Carbide (SiC);Wide bandgap devices
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-182756 (URN)10.1109/EPE.2015.7309314 (DOI)000377101802046 ()2-s2.0-84965026745 (Scopus ID)
Conference
Power Electronics and Applications (EPE’15 ECCE-Europe), 2015 17th European Conference on
Funder
StandUp
Note

QC 20160303

Available from: 2016-02-23 Created: 2016-02-23 Last updated: 2017-05-29Bibliographically approved
4. Humidity testing of SiC power MOSFETs
Open this publication in new window or tab >>Humidity testing of SiC power MOSFETs
2016 (English)In: 2016 IEEE 8th International Power Electronics and Motion Control Conference, IPEMC-ECCE Asia 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, 3131-3136 p., 7512796Conference paper, Published paper (Refereed)
Abstract [en]

Humidity and outdoor application are a challenge for Silicon (Si) and Silicon Carbide (SiC) applications. This paper investigates the effect of humidity on SiC power MOSFET modules in a real application where no acceleration factors such as pressure or high temperature are applied. Since SiC devices can operate at higher temperature than Si, the high-temperature acceleration factor may be obsolete. Moreover, the humidity might be more critical when the temperature inside the converter enclosure and modules housing is varying with daily temperature variations and weather constraints in harsh environments. The breakdown voltages of the humidity-exposed modules are monitored regularly over a extended period of time in order to detect any increase of leakage current which indicates humidity-induced degradation. After 630 hours, the modules operated outdoor presented an increased leakage current at 1.2 kV and over the whole range of applied voltage.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016
Keyword
corrosion, failure analysis, humidity, multichip packaging, Power MOSFETs, reliability, Silicon Carbide (SiC), Atmospheric humidity, MOSFET devices, Motion control, Power control, Power electronics, Reliability analysis, Silicon, Silicon carbide, Soldered joints, Acceleration factors, Daily temperatures, Harsh environment, Induced degradation, Real applications, Silicon carbides (SiC), Power MOSFET
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-197148 (URN)10.1109/IPEMC.2016.7512796 (DOI)000390949703049 ()2-s2.0-84983347998 (Scopus ID)9781509012107 (ISBN)
Conference
8th IEEE International Power Electronics and Motion Control Conference, IPEMC-ECCE Asia 2016, Hefei, China, 22 May 2016 through 26 May 2016
Note

QC 20161213

Available from: 2016-12-13 Created: 2016-11-30 Last updated: 2017-07-06Bibliographically approved
5. Humidity Testing of SiC Power MOSFETs – An Update
Open this publication in new window or tab >>Humidity Testing of SiC Power MOSFETs – An Update
2017 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The effect of humidity on SiC Power MOSFET modules is investigated in a real application. Four modules are operated outdoor and four modules are operated indoor in identical setups, while their breakdown voltages are monitored regularly. The evolution of the leakage current, indicating humidity-induced degradation is observed.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-207764 (URN)
Conference
EPE 2017 ECCE EUROPE
Note

QC 20170530

Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2017-05-29Bibliographically approved
6. Short-Circuit Protection Circuits for Silicon Carbide Power Transistors
Open this publication in new window or tab >>Short-Circuit Protection Circuits for Silicon Carbide Power Transistors
Show others...
2016 (English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, ISSN 0278-0046, Vol. 63, no 4, 1995-2004 p., ITIEDArticle in journal (Refereed) Published
Abstract [en]

An experimental analysis of the behavior under short-circuit conditions of three different siliconcarbide (SiC) 1200-V power devices is presented. It is found that all devices take up a substantial voltage, which is favorable for detection of short circuits. A transient thermal device simulation was performed to determine the temperature stress on the die during a short-circuit event, for the SiC MOSFET. It was found that, for reliability reasons, the short-circuit time should be limited to values well below Si IGBT tolerances. Guidelines toward a rugged design for short-circuit protection (SCP) are presented with an emphasis on improving the reliability and availability of the overall system. A SiC device driver with an integrated SCP is presented for each device-type, respectively, where a shortcircuit detection is added to a conventional driver design in a simple way. The SCP driver was experimentally evaluated with a detection time of 180 ns. For all devices, short-circuit times well below 1 µs were achieved.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2016
Keyword
BJT Bipolar junction transistor (BJT), Driver circuits, Failure analysis, Fault detection, Fault protection, JFET Power MOSFET, Semiconductor device reliability, Short-circuit current, Silicon Carbide (SiC), Wide band gap semiconductors, driver circuits, failure analysis, fault detection, fault protection, junction field-effect transistor (JFET), power MOSFET, semiconductor device reliability, short-circuit current, silicon carbide (SiC), wide-bandgap semiconductors
National Category
Engineering and Technology
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-185456 (URN)10.1109/TIE.2015.2506628 (DOI)000372645900001 ()2-s2.0-84963729279 (Scopus ID)
Funder
VINNOVA, 76454
Note

QC 20160419

Available from: 2016-04-19 Created: 2016-04-19 Last updated: 2017-05-29Bibliographically approved
7. Comparison of Thermal Stress during Short-Circuit in Different Types of 1.2 kV SiC Transistors Based on Experiments and Simulations
Open this publication in new window or tab >>Comparison of Thermal Stress during Short-Circuit in Different Types of 1.2 kV SiC Transistors Based on Experiments and Simulations
Show others...
2016 (English)In: Silicon Carbide and Related Materials 2016 / [ed] Konstantinos Zekentes, Konstantin V. Vasilevskiy and Nikolaos Frangis, Trans Tech Publications Inc., 2016, Vol. 897, 595-598 p.Conference paper, Published paper (Refereed)
Abstract [en]

The temperature evolution during a short-circuit in the die of three different Silicon Carbide1200-V power devices is presented. A transient thermal simulation was performed based on the reconstructedstructure of commercially available devices. The location of the hottest point in the device iscompared. Finally, the analysis supports the necessity to turn off short-circuit events rapidly in orderto protect the device after a fault.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2016
Series
Materials Science Forum, ISSN 0255-5476 ; 897
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-207757 (URN)10.4028/www.scientific.net/MSF.897.595 (DOI)2-s2.0-85020002693 (Scopus ID)9783035710434 (ISBN)
Conference
11th European Conference on Silicon Carbide and Related Materials, ECSCRM 2016, Halkidiki, Greece, 25 September 2016 through 29 September 2016
Funder
Swedish Energy AgencyVINNOVA
Note

QC 20170530

Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2017-10-20Bibliographically approved
8. Introduction of SiC MOSFETs in Converters based on Si IGBTs: A Reliability and Efficiency Analysis
Open this publication in new window or tab >>Introduction of SiC MOSFETs in Converters based on Si IGBTs: A Reliability and Efficiency Analysis
Show others...
2017 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) have the potential to increase the power density in power electronics converters compared to the currently used silicon (Si). Their benefits are higher efficiency, higher switching speeds, and higher operating temperatures. Moreover, SiC MOSFETs, which are normally-off, offer the possibility to directly replace Si Isolated-Gate-BipolarTransistors (IGBTs) in already existing converter designs with minimal circuit changes. Nevertheless, as an emerging technology, the reliability performance remains to be investigated. A reliability analysis has been performed based on a full-bridge resonant converter rated at 60 kW for modern Electrostatic Precipitator (ESP) power supplies. This analysis shows that introducing SiC devices will increase the lifetime of the converter while reducing the losses. The investment costs of replacing the Si IGBTs with SiC MOSFETs can thus be covered with the reduction of the losses over the economical operational lifetime. Furthermore, a theoretical analysis on how introducing SiC MOSFETs could increase the power density of the converter while maintaining the efficiency and the reliability. Finally, an analysis on introducing redundancy as a way to improve the reliability of the system has been performed.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-207751 (URN)
Conference
IEEE International Future Energy Electronics Conference 2017 – ECCE Asia
Note

QC 20170530

Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2017-05-29Bibliographically approved
9. Investigation of the Surge Current Capability of the Body Diode of SiC MOSFETs for HVDC Applications
Open this publication in new window or tab >>Investigation of the Surge Current Capability of the Body Diode of SiC MOSFETs for HVDC Applications
Show others...
2016 (English)In: 2016 18TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'16 ECCE EUROPE), IEEE, 2016Conference paper, Published paper (Refereed)
Abstract [en]

The surge current capability of the body-diode of SiC MOSFETs is experimentally analyzed in order to investigate the possibility of using SiC MOSFETs for HVDC applications. SiC MOSFET discrete devices and modules have been tested with surge currents up to 10 times the rated current and for durations up to 2 ms. Although the presence of stacking faults cannot be excluded, the experiments reveal that the failure may occur due to the latch-up of the parasitic n-p-n transistor located in the SiC MOSFET.

Place, publisher, year, edition, pages
IEEE, 2016
Series
European Conference on Power Electronics and Applications, ISSN 2325-0313
Keyword
Silicon Carbide (SiC), MOSFET, Diode, Reliability, Faults, Voltage Source Converter (VSC)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-197013 (URN)10.1109/EPE.2016.7695448 (DOI)000386637300197 ()2-s2.0-84996938039 (Scopus ID)
Conference
18th European Conference on Power Electronics and Applications (EPE), SEP 05-09, 2016, GERMANY
Note

QC 20161209

Available from: 2016-12-09 Created: 2016-11-28 Last updated: 2017-05-29Bibliographically approved

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