Thermoelectrical Effect in SiC for High-Temperature MEMS Sensors

122 Pages·2018·5.65 MB·English

by  Toan Dinh, Nam-Trung Nguyen, Dzung Viet Dao

SPRINGER BRIEFS IN
APPLIED SCIENCES AND TECHNOLOGY
Toan Dinh
Nam-Trung Nguyen
Dzung Viet Dao
Thermoelectrical
Effect in SiC
for High-
Temperature
MEMS Sensors
123
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Toan Dinh Nam-Trung Nguyen
(cid:129)
Dzung Viet Dao
Authors
Andreas Oechsner
Editor
Thermoelectrical Effect
in SiC for High-Temperature
MEMS Sensors
123
Authors Editor
Toan Dinh Andreas Oechsner
Queensland Micro- andNanotechnology Esslingen University of Applied Sciences
Centre(QMNC) Esslingen am Neckar,Germany
GriffithUniversity
Brisbane, QLD,Australia
Nam-Trung Nguyen
Queensland Micro- andNanotechnology
Centre(QMNC)
GriffithUniversity
Brisbane, QLD,Australia
Dzung Viet Dao
Schoolof Engineering andBuilt
Environment
GriffithUniversity
Southport, QLD,Australia
ISSN 2191-530X ISSN 2191-5318 (electronic)
SpringerBriefs inApplied SciencesandTechnology
ISBN978-981-13-2570-0 ISBN978-981-13-2571-7 (eBook)
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Preface
Therehasbeengreatinterestandemergingdemandforthedevelopmentofaerospace
sensing technology. This technology is used for sensing a wide range of systems
workinginharshenvironments.Thesensingapplicationsinhostileconditionsinclude,
butnotlimitedto,deepspaceexploration,combustionmonitoringandobservationof
hypersonicaircraft.Tomaintainthesafetyandefficiencyofinstrumentationusedin
harshenvironmentindustries,advancedhealthmonitoringtechnologiesarerequiredto
developsensingnetworkswhichfunctionreliablyinharshenvironments.However,
thecurrenttechnologyhasfacedgreatchallengesinprovidingsustainablesolutionsfor
thegrowthandstabilityofmicro-/nanosystems.Forexample,thedifficultyoflocating
sensingandelectroniccomponentsinhostileenvironmentshasledtotheutilisationof
indirect measurement approaches which are expensive and inaccurate. These tech-
nologieshaveemployedconventionalmaterialssuchassilicon,whichcannotwith-
standhigh-temperatureandhigh-corrosiveenvironments.
In addition, the resource sector, which includes mining, oil and gas and
geothermal industries, is one of the driving forces of the global economy. The oil
andgasdeliveryinfrastructureisrapidlyageing.Internalcorrosionandmechanical
straincancausetheleakageingasandoilpipelines,leadingtocatastrophicfailures,
death,injuryandenvironmentalimpacts.Numeroussensortechnologieshavebeen
used for monitoring and accident prevention purposes. However, most of the
sensors are bulky or also based on materials like silicon (Si), which is not suitable
for long-time operation in high-temperature environments found in pipelines, and
geothermal and mining applications. Therefore, there have been new requirements
for sensing technologies operating beyond the capability of Si sensing.
Siliconcarbide(SiC)hasbeendevelopedforsensingsystemsoperatinginharsh
conditions including high-temperature, high-corrosion, high-voltage/power and
high-frequency applications. Tremendous progress has been made in the develop-
ment of microelectromechanical system (MEMS) sensors which employ SiC as a
functional sensing material. These sensors have been commercialised for temper-
aturesupto300°C.Anumberofrecentstudieshavesuccessfullydemonstratedthe
application of SiC sensors for high temperatures above 500 °C, indicating a great
potential for using this material for sensing in harsh environments.
v
vi Preface
ThisbookfocusesontherecentdevelopmentofSiCthermalsensorsemploying
high thermoelectrical effects in SiC at high temperatures. The thermoelectrical
effect in SiC refers to a change in the electrical properties of SiC with temperature
variation. This book will introduce the thermoelectrical effect in the form of the
following physical effects: thermoresistive, thermoelectric, thermoelectronic and
thermocapacitive effects in single and multiple SiC layers. The important charac-
teristics of SiC materials and the fabrication processes for SiC MEMS are men-
tioned. The recent development of SiC sensing devices including temperature
sensors, thermal flow sensors and convective inertial sensors is reviewed. The
futureprospectsofSiCthermoelectricalsensingdevicesarediscussedinthisbook.
Brisbane, Australia Toan Dinh
Brisbane, Australia Nam-Trung Nguyen
Southport, Australia Dzung Viet Dao
Acknowledgements
The authors would like to acknowledge the support from Queensland Micro- and
NanotechnologyCentre(QMNC)andSchoolofEngineeringandBuiltEnvironment
atGriffithUniversity,Australia.Theauthorsaregratefulforthecontributionofthe
membersofMEMSgroupatQMNC,includingDr.Hoang-PhuongPhan,Dr.Afzaal
Qamar,Mr.VivekananthanBalakrishnan,Mr.Tuan-KhoaNguyen,Mr.AlanIacopi,
Ms. Leonie Hold, Mr. Glenn Walker and Mr. Abu Riduan Md Foisal, to the
SiC MEMS project. The authors would like to thank the financial support from
AustralianResearchCouncilgrantsLP150100153andLP160101553.ToanDinhis
gratefulthesupportfromGriffithUniversity&SimonFraserUniversityCollaborative
Travel Grants Scheme 2017 and Australian Nanotechnology Network
(ANN) Overseas Travel Fellowship 2018. We thank all authors and publishers for
theirgraciousnesstograntpermissiontoreusefiguresandtablesinthisbook.
vii
Contents
1 Introduction to SiC and Thermoelectrical Properties . . . . . . . . . . . . 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Silicon Carbide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Growth of SiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Thermoelectrical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.5 High-Temperature SiC MEMS Sensors . . . . . . . . . . . . . . . . . . . . 7
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Fundamentals of Thermoelectrical Effect in SiC. . . . . . . . . . . . . . . . 11
2.1 Thermoresistive Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.1 Physical Parameters and Definitions in Semiconductors . . . 13
2.1.2 Single-Crystalline SiC . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.3 Polycrystalline SiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1.4 Amorphous SiC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2 Thermoelectronic Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.3 Thermocapacitive Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.4 Thermoelectric Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.5 Recent Advances in Characterisation of Thermoelectrical
Effects in SiC at High Temperatures . . . . . . . . . . . . . . . . . . . . . . 20
2.5.1 Experimental Set-up for Characterisation
of Thermoelectrical Effect . . . . . . . . . . . . . . . . . . . . . . . . 20
2.5.2 Thermoresistive Effect in Single Layer of SiC. . . . . . . . . . 21
2.5.3 Thermoelectrical Effect in Multi-layers of SiC. . . . . . . . . . 29
2.6 4H-SiC p–n Junctions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.7 Other Thermoelectrical Effects at High Temperatures . . . . . . . . . . 34
2.7.1 Thermoelectric Effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.7.2 Thermocapacitive Effect. . . . . . . . . . . . . . . . . . . . . . . . . . 36
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
ix
x Contents
3 Desirable Features for High-Temperature SiC Sensors. . . . . . . . . . . 43
3.1 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.2 Linearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.3 Thermal Time Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.4 Low Power Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.5 Stability and Other Desirable Features . . . . . . . . . . . . . . . . . . . . . 49
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4 Fabrication of SiC MEMS Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.1 Growth and Doping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.1.1 Growth of SiC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.1.2 Doping of SiC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.2 Etching of SiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.2.1 Electrochemical Etching. . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.2.2 Chemical Etching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.2.3 Dry Etching or Reactive-Ion Etching (RIE). . . . . . . . . . . . 60
4.3 Ohmic and Schottky Contacts to SiC. . . . . . . . . . . . . . . . . . . . . . 60
4.3.1 Ohmic Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.3.2 Schottky Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.4 Fabrication Processes of SiC MEMS Sensors. . . . . . . . . . . . . . . . 67
4.4.1 Surface Micromachining . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.4.2 Bulk Micromachining . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.4.3 Fabrication of MEMS Device with Integrated Cooling
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
5 Impact of Design and Process on Performance of SiC Thermal
Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.1 Substrate Influence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.2 Doping Influence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.3 Morphologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.4 Deposition Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.5 Geometry and Dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
6 Applications of Thermoelectrical Effect in SiC . . . . . . . . . . . . . . . . . 85
6.1 Temperature Sensors, Temperature Control/Compensation
and Thermal Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.1.1 Thermistors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.1.2 p–n Junction Temperature Sensors . . . . . . . . . . . . . . . . . . 88
6.2 Thermal Flow Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
6.2.1 Hot-Wire and Hot-Film Flow Sensors. . . . . . . . . . . . . . . . 90
6.2.2 Calorimetric Flow Sensors . . . . . . . . . . . . . . . . . . . . . . . . 94
6.2.3 Time-of-Flight Flow Sensors . . . . . . . . . . . . . . . . . . . . . . 95