High-Temperature Analog and Mixed-Signal Integrated Circuits in Bipolar Silicon Carbide ...

125 Pages·2017·9.43 MB·English

High-Temperature Analog and Mixed-Signal
Integrated Circuits in Bipolar Silicon Carbide
Technology
RAHELEH HEDAYATI
Doctoral Thesis in Information and Communication Technology
KTH Royal Institute of Technology
Stockholm, Sweden 2017
KTH School of Information and
Communication Technology
TRITA-ICT 2017:16 SE-164 40, Kista
ISBN 978-91-7729-496-2 SWEDEN
Akademisk avhandling som med tillstånd av Kungl Tekniska högskolan framlägges
till offentlig granskning för avläggande av doktorsexamen i Informations- och kom-
munikationsteknik fredagen den 29 september 2017 klockan 13:00 i Ka-Sal A (Sal
Östen Mäkitalo), KTH, Kistagången 16, Kista.
Cover image: Microphotograph of the fabricated 8-bit R-2R DAC and layout view
of the 4-bit flash ADC implemented in SiC bipolar technology.
© Raheleh Hedayati, September 2017
Tryck: Universitetsservice US-AB
For my family
Neither you nor I know the mysteries of eternity,
Neither you nor I read this enigma;
You and I only talk this side of the veil;
When the veil falls, neither you nor I will be here.
Omar Khayyam
Theastronomer,mathematicianandpoetofPersia
i
Abstract
Siliconcarbide(SiC)integratedcircuits(ICs)canenabletheemergenceof
robustandreliablesystems,includingdataacquisitionandon-sitecontrolfor
extremeenvironmentswithhightemperatureandhighradiationsuchasdeep
earthdrilling,spaceandaviation,electricandhybridvehicles,andcombustion
engines. In particular, SiC ICs provide significant benefit by reducing power
dissipation and leakage current at temperatures above 300 ◦C compared to
the Si counterpart. In fact, Si-based ICs have a limited maximum operating
temperaturewhichisaround300◦C forsilicononinsulator(SOI).Owingto
itssuperiormaterialpropertiessuchaswidebandgap,threetimeslargerthan
Silicon, and low intrinsic carrier concentration, SiC is an excellent candidate
for high-temperature applications.
In this thesis, analog and mixed-signal circuits have been implemented
using SiC bipolar technology, including bandgap references, amplifiers, a
master-slave comparator, an 8-bit R-2R ladder-based digital-to-analog con-
verter (DAC), a 4-bit flash analog-to-digital converter (ADC), and a 10-bit
successive-approximation-register (SAR) ADC. Spice models were developed
atbinnedtemperaturepointsfromroomtemperatureto500◦C,tosimulate
and predict the circuits’ behavior with temperature variation. The high-
temperature performance of the fabricated chips has been investigated and
verified over a wide temperature range from 25 ◦C to 500 ◦C. A stable gain
of 39 dB was measured in the temperature range from 25 ◦C up to 500 ◦C
for the inverting operational amplifier with ideal closed-loop gain of 40 dB.
Although the circuit design in an immature SiC bipolar technology is
challengingduetothelowcurrentgainofthetransistorsandlackofcomplete
AC models, various circuit techniques have been applied to mitigate these
problems. This thesis details the challenges faced and methods employed for
devicemodeling,integratedcircuitdesign,layoutimplementationandfinally
performanceverificationusingon-wafercharacterizationofthefabricatedSiC
ICs over a wide temperature range.
Keywords: silicon carbide (SiC), bipolar junction transistor (BJT), high
temperature,SiCintegratedcircuit,SpiceGummel-Poon(SGP),operational
amplifier (opamp), negative feedback amplifier, bandgap reference, master-
slave comparator, digital-to-analog converter (DAC), analog-to-digital con-
verter (ADC), flash ADC, successive approximation register (SAR) ADC.
ii
Sammanfattning
Integrerade kretsar (IC) i kiselkarbid (SiC) kan möjliggöra framväxten av ro-
busta och tillförlitliga system, såsom för datainsamling och kontroll på plats i
extremamiljöermedhögtemperaturochhögstrålning,tillexempeldjup-borrning,
rymd och luftfart, elektriska och hybridfordon och förbränningsmotorer. Speciellt
gerSiC-kretsarbetydandefördelargenomattminskaeffektförlusterochläckström-
marvidtemperatureröver300◦Cjämförtmedkisel-motparten. Faktumärattkisel-
baseradeICharenbegränsadmaximalarbetstemperatursomäromkring300◦C för
"silicononisolator"(SOI).På grundavsinaöverlägsnamaterialegenskaper,såsom
brett bandgap, tre gånger större än kisel, och låg intrinsisk laddningsbärarkoncen-
tration, är SiC en utmärkt kandidat för högtemperaturapplikationer.
I den här avhandlingen har analoga och blandade signalkretsar implementer-
ats med hjälp av SiC-bipolär teknik, inklusive bandgapsreferenser, förstärkare, en
master-slavekomparator, en 8-bitars R-2R digital-till-analog-omvandlare (DAC),
en 4-bitars flash analog-till-digital-omvandlare (ADC) och en 10-bitars successiv-
approximation-register (SAR) ADC. Spicemodeller utvecklades vid valda temper-
aturer från rumstemperatur till 500◦C, för att simulera och förutsäga kretsarnas
beteendevidtemperaturvariation. Kretsarnashögtemperaturprestandaharunder-
söktsochverifieratsöverettbretttemperaturområdefrån25◦C till500◦C. Ensta-
bilförstärkningav39dBuppmättesitemperaturområdetfrån25◦C upptill500◦C
fördeninverterandeoperationsförstärkarenmeddenidealaslutnaslingförstärknin-
gen på 40 dB.
Även om kretsdesign i en omogen SiC-bipolär teknik är utmanande på grund
av transistorernas låga strömförstärkning och brist på kompletta AC-modeller har
olika kretstekniker tillämpats för att mildra dessa problem. Denna avhandling
beskriverdeutmaningarsommöttesochdemetodersomanvändesförkomponent-
modellering, integrerad kretsdesign, layoutimplementering och slutlig prestatan-
daverifiering med användning av on-waferkarakterisering av de tillverkade SiC-
kretsarna över ett brett temperaturintervall.
Acknowledgements
Many people have supported and encouraged me during the past few years as a
Ph.D. student and deserve my deepest gratitude.
First,Iwouldliketoexpressmysinceregratitudeandappreciationtomysuper-
visor, Prof. Carl-Mikael Zetterling (Bellman) for his encouragement, inspiration,
and support which brought to the completion of this thesis.
I am also grateful to Prof. Ana Rusu, my co-supervisor, for the insightful
discussions during these years and also her constructive feedback on my papers.
Assoc. Prof. Gunnar Malm is appreciated for valuable discussions, his kind
support in the measurements and for always offering a new approach to problems.
I am also thankful for the support from Prof. Mikael Östling and Prof. Anders
Hallén.
I am thankful to Docent Saul Rodriguez for careful review of this thesis and
also for his kind support in my research life at KTH. I am indebted to Dr. Luigia
(Gina) Lanni for the fabrication of the first batch and fruitful collaboration. I am
alsothankfultoShuobenHouforthefabricationofthesecondbatch. Iwouldliketo
appreciate Bengt Molin for his kind support and Dr. David Martin for introducing
me to the clean room processing.
I am also thankful to my colleagues in the SiC group for the kind support
during these years, I learned something from all of you: Dr. Hossein Elahipanah
(for the interesting discussions), Dr. Arash Salemi, Dr. Saleh Kargarrazi, Ye Tian
(William), Katarina Smedfors, Dr. Sethu Saveda Suvanam, Dr. Benedetto Buono,
Muhammad Shakir, Muhammad Waqar Hussain, and Mattias Ekström especially
for daily Swedish lunches; Tack för att jag fick träna min svenska!
IwouldliketoextendmygratitudetoallthepastandpresentmembersofEKT
especially Nikola Ivanisevic for the valuable discussions on the ADC design, Pana-
giotis (Panos) Chaourani, Dr. Janko Katic, Babak Taghavi, Dr. Maryam Olyaei,
Dr. Tao Sha, Dr. Tingsu Chen, Dr. Masoumeh (Azin) Ebrahimi, Ali (Pouria)
Asadollahi, Ahmad Abedin, Dr. Raul Onet, Konstantinos Garidis, Dr. Eugenio
Dentoni, Dr. Anders Eklund, Ganesh Jayakumar, Dr. Muhammad Usman, Szy-
mon Sollami Delekta, Laura Zurauskaite, Dr. Anderson Smith, Dr. Maziar Amir
ManouchehryNaiini,TimoSöderqvist,ChristianRidder,DocentHenryRadamson,
Dr. Margareta Linarsson, and Dr. Christof Henkel. I am also grateful to all my
friends for enriching my out-of-work life.
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iv
I am deeply indebted to three masters, Prof. Hooman Nabovati, Prof. Khalil
Mafinezhad,andProf. RezaLotfiforhavingintroducedmetothefascinatingworld
of Electronics and IC design during my Bachelor in Iran.
I would like to acknowledge the funding support from the Swedish Foundation
for Strategic Research (SSF). I also acknowledge Nils and Hans Backmark for the
travel grant.
My warmest and heartfelt gratitude goes to my family members: my parents,
mybrother,myhusbandandmylittleson. Thisthesisisdedicatedtothem. Special
thanks go to my mother for her continuous support, endless love, and for believing
in me. My deepest gratitude goes to my husband, Hojat Khosrowjerdi, for all the
love, support, and patience. I am blessed to have Nikan, our cute son, by our side.
Thank you for bringing all the happiness and joy.
Raheleh Hedayati
Stockholm, August 2017
Contents
Abstract i
Sammanfattning ii
Acknowledgements iii
Contents v
List of Acronyms and Symbols vii
List of Publications ix
Summary of Appended Papers xi
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Research objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Research contribution . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Thesis structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 SiC device modeling 7
2.1 SiC material properties . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 Crystal structures . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.2 Electrical properties . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Spice Gummel-Poon (SGP) model . . . . . . . . . . . . . . . . . . . 12
2.3 SiC BJT parameter extraction . . . . . . . . . . . . . . . . . . . . . 15
2.4 Integrated resistor characterization . . . . . . . . . . . . . . . . . . . 20
3 Negative feedback amplifiers 25
3.1 Charge amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.1.1 Circuit design . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.1.2 Measurement results . . . . . . . . . . . . . . . . . . . . . . . 34
3.2 Voltage amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.2.1 Circuit design and simulation . . . . . . . . . . . . . . . . . . 37
v
vi CONTENTS
3.2.2 Measurement results . . . . . . . . . . . . . . . . . . . . . . . 39
3.3 Operational amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3.1 Circuit design and simulation . . . . . . . . . . . . . . . . . . 43
3.3.2 Measurement results . . . . . . . . . . . . . . . . . . . . . . . 44
3.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4 Analog-to-digital converters 51
4.1 Data converters overview . . . . . . . . . . . . . . . . . . . . . . . . 51
4.1.1 Principle of analog-to-digital conversion . . . . . . . . . . . . 51
4.1.2 ADC performance metrics . . . . . . . . . . . . . . . . . . . . 54
4.2 Building blocks of SiC ADCs . . . . . . . . . . . . . . . . . . . . . . 55
4.2.1 Bandgap voltage references . . . . . . . . . . . . . . . . . . . 55
4.2.2 Digital-to-analog converter (DAC) . . . . . . . . . . . . . . . 63
4.2.3 Master-slave comparator . . . . . . . . . . . . . . . . . . . . . 73
4.3 SiC analog-to-digital converters . . . . . . . . . . . . . . . . . . . . . 76
4.3.1 A 4-bit bipolar Flash ADC . . . . . . . . . . . . . . . . . . . 77
4.3.2 A 10-bit bipolar SAR ADC . . . . . . . . . . . . . . . . . . . 85
5 Summary and future outlook 97
Bibliography 99