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High Temperature Electronics for Intelligent Harsh Environment Sensors
PWIG Workshop
Laura J. Evans
NASA Glenn Research Center Cleveland, OH 44135
The development of intelligent instrumentation systems is of high interest in both public and
private sectors. In order to obtain this ideal in extreme environments (i.e., high temperature, extreme vibration, harsh chemical media, and high radiation), both sensors and electronics must be developed concurrently in order that the entire system will survive for extended periods of time.
The semiconductor silicon carbide (SiC) has been studied for electronic and sensing applications in extreme environment that is beyond the capability of conventional semiconductors such as silicon. The advantages of SiC over conventional materials include its near inert chemistry, superior thermomechanical properties in harsh environments, and electronic properties that include high breakdown voltage and wide bandgap. An overview of SiC sensors and electronics work ongoing at NASA Glenn Research Center (NASA GRC) will be presented. The main focus will be two technologies currently being investigated: 1) harsh environment SiC pressure transducers and 2) high temperature SiC electronics. Work highlighted will include the design, fabrication, and application of SiC sensors and electronics, with recent advancements in state-of-the-art discussed as well. These combined technologies are studied for the goal of developing advanced capabilities for measurement and control of aeropropulsion systems, as well as enhancing tools for exploration systems.
https://ntrs.nasa.gov/search.jsp?R=20080033116 2018-07-05T02:44:00+00:00Z
Standards
Certification
Education & Training
Publishing
Conferences & Exhibits
High Temperature
Electronics for
Intelligent Harsh
Environment SensorsLaura J. Evans
NASA Glenn Research Center
May 8 2008
2
Presenter
• Laura J. Evans holds BS (2002) and MS (2003) degrees in Mechanical
Engineering from Northwestern University. Since 2004, she has worked
at NASA Glenn Research Center in the Microsystems Fabrication Clean
Room on the advancement of Silicon Carbide technologies and
Chemical Sensors for aerospace applications. Her main area of interest
is MEMS processing techniques for silicon carbide and she has
extensive experience in clean room microfabrication processing. This
work includes development of processes that enable new advances in
high temperature sensor structures. She has also co-authored
publications in the areas of harsh environment electronics and sensors.
http://www.grc.nasa.gov/WWW/SiC
3
High Temperature SiC
Electronics
• Microsystems overview
• Benefits to NASA
• Electronic and sensing applications in extremeenvironments
• SiC - advantages for harsh environmentapplications
• Facilities
• NASA GRC advancements
• Harsh Environment Pressure Transducers
– Overview
– Concept
– State-of-the-art at NASA GRC
• High Temperature SiC Electronics
– Overview
– Testing
– Junction Field Effect Transistor
– Semiconductor IC: Amplifiers
– State-of-the-art at NASA GRC
• Conclusion
• Acknowledgements
Outline
Harsh Environment Pressure
Transducer
4
A
C
T
U
A
T
O
R
S
S
E
N
S
O
R
S
Ph
ysi
cal/
Ch
emic
al
Sig
nal
Communication
POWER
Mec
ha
nic
al/
Ele
ctri
cal/
Op
tica
l
Syst
em O
utp
ut
Electrical/Optical
Control & Communication
Analog
Signal
Processing
Digital
Signal
Processing
Large-scale integrated electronics are crucial to highly advanced
MEMS.
Microsystems Overview
5
Intelligent Propulsion Systems
Some of these applications require prolonged T > 400 °C operation
Space Exploration Vision: Power
Management and Distribution
Venus ExplorationMore Electric + Distributed Control Aircraft
High Temperature MEMS and Electronics
Benefits to NASA
6
Harsh Environment
Packaging
(2000 hours at 500 °C)
Range of Physical and Chemical Sensors
for Harsh Environments
High Temperature
Signal Processing
and Wireless
Long Term: High
Temperature “Lick
and Stick” Systems
• Applications in environments of high temperature,extreme vibration, harsh chemical media, high radiation– Measurement and control of challenging systems
– Aircraft engines
– Automotive
– Well drilling
– Enhanced tools for exploration systems
• Requires development of integrated sensors, electronics,and packaging
Applications for Harsh Environment Sensors
and Electronics
7
• Current technology - suitable up to 350 °C:
– T < 150 °C (302 °F), silicon is used in almost all integrated circuits in usetoday.
– T < 300 °C (572 °F), well-developed Silicon-On-Insulator (SOI) IC’savailable for low-power logic and signal processing functions.
– T > 350 °C (662 °F), other wide-bandgap semiconductors such as SiC,GaN, or diamond are needed.
• Why SiC for harsh environments?
– Near inert chemistry due to high bonding energy
– Similar processing as silicon
– Technology at a level where single crystal wafers can be purchased
– Superior thermomechanical properties (greater hardness, higher Young’smodulus, high thermal conductivity)
– Superior electronic properties (wide bandgap, high breakdown electricfield, high carrier saturation velocity)
• Benefits:
– Improved reliability
– Reduced cooling system: reduced cost, volume, and weight of controlsystems, reduction in fuel consumption and pollution
– Direct sensing and control in harsh environment e.g., turbine engine
SiC - advantages for harsh environment
applications
8
• Significant in-house capabilities for a range of micro/nano sensor and electronics
development
• Capabilities range from semiconductor material growth to micro-device
fabrication to packaging and testing
Microdevices
Characterization Facilities
Microsystems
Fabrication Clean
Rooms: Class 100 and
1000
NASA Glenn SiC Microsystem Development
Facilities
9
500 °C Durable Chip
Packaging
And Circuit Boards
(L. Chen, 2002 GRC R&T
Report)
500 °C Durable Metal-SiC
Contacts
(R. Okojie, 2000 GRC R&T
Report)
Key fundamental high temperature electronic materials and processing
challenges have been faced and overcome by systematic basic
materials processing research (fabrication and characterization).
Additional advancements in device design, insulator processing, etc., also made.
100 m
Improvements in SiC
Microfabrication Processes
(L. Evans, 2006 GRC R&T
Report)
Previous Key NASA Glenn Advancements
10
Objective:Develop high temperature (500 to 600 °C)
SiC pressure sensors for:
Engine health monitoring with wireless
data transmission
Active combustion control
Challenges:Reliable device packaging: failure at
wire bonds
Failure due to strains/stresses caused
by CTE mismatch during
heating/cooling
Premature failure of diaphragms due to
stress concentration
500 °C SiC pressure sensor
Real world application: pressure
sensor installed in engine test
Harsh Environment SiC Pressure Sensors:
an Overview
The developed technology that has solved
these packaging challenges has been
licensed to Endevco Corporation, San
Juan Capistrano, CA
11
Concept
• Piezoresistive SiC Pressure
Sensor
Okojie et. al. IEEE Sensors, Oct 2004
0
2
4
6
8
10
12
14
16
18
20
0 10 20 30 40 50 60 70 80 90 100Applied Pressure (psi)
Net
Bri
dge
Ou
tpu
t (m
V)
Vin = 5 V
BQ0345-13-R10-C09-PS02-1-29
Sensitivity: 36.60 μV/V/psi @ 25oC
25 oC
100 oC
200 oC
300 oC
400 oC
A
BC
D
Vin+
Vin-
Vo+Vo-
R1+ R1 R4- R
4
R3+ R3
R2- R2
12
MEMS-DCA Sensor Attributes:Eliminates failures associated with wire
bonds at high temperature
Reduces thermomechanical stress by
decoupling sensor from package
SensorGlass sealedGap
AlN
Kovar tube
Contact wire
Thermocouplehole
Reference cavity
MEMS-DCA (Direct Chip Attach) packaged SiC
pressure sensor
Net output voltage of three SiC pressure sensors
tested up to 600 °C
Harsh Environment SiC Pressure Sensors
0
2
4
6
8
10
12
0 50 100 150 200 250 300
Pressure (psi)
Net
Ou
tpu
t (m
V)
121(600C)-Net Up (mV) 122(600C)-Net Up (mV) 123(600C)-Net Up (mV)
121(25C)-Net Up (mV) 122(25C)-Net Up (mV) 123(25C)-Net Up (mV)
13
Objective:Develop high temperature (500 °C) SiC
electronics for:
Wireless sensors
Sensor signal conditioning – amplifier
for SiC pressure sensor
Distributed engine control – sensor
multiplexing
Challenges:Electronic structure robust against high
temperature degradation
Thermally activated degradation
mechanisms at interfaces
Metal-SiC
Insulator-SiC
Thermally activated degradation
mechanisms at system level
Metals (e.g., contacts)
Insulators
Packaging
High Temperature SiC Electronics: an
Overview
Testing of SiC JFET and SiC amplifiers. Packagingdescribed in L.Y. Chen et. al., IMAPS Int. Conf.High Temp. Electronics, 2006
1 mm
14
1 cm
200μm/10μm
6H-SiC JFET
100 m
150 m
Differential
Amplifier
Boards with chips reside in ovens.
Continuous electrical testing at 500 °C.
Wires to test instrumentation.
Oxidizing room air ambient.
Testing discrete JFETs and integrated circuits at same time.
High Temperature SiC Electronics: Testing
15
Junction Field Effect Transistor (JFET)
• Epitaxial pn-junction gate
structure
• Low operating gate
current - more robust at
high temperatures
• Mesa-etched p+ epi-gate
structure to avoid defects
and extreme activation
temp of high-dose p-type
implants
100 m
Drain
Source
200 m
10
m
Gate
Spry et. al. Mater. Sci. Forum, 2008
16
Differential and Inverting Amplifiers (diff-
amp and inv-amp)
• Amplifiers:
– Control of motors or servos
– Signal amplificationapplications
• Diff-amp:– Two source-coupled
20 m/10 m JFET
– Three epitaxial load resistors(545 )
• Inv-amp:– 80 m/10 m JFET
– 20-square(516 k @ 500 °C)epitaxial load resistor
• Goal: more complex analogand digital ICs, using multiplemetal interconnect layers
Differential
Amplifier
Inverting
Amplifier
17
Current-voltage characteristics are very good and stable after 4000 hoursEnables realization of analog integrated circuits (amplifiers, oscillators)
Excellent turn-off characteristics, ON to OFF current ratioEnables realization of digital circuits.
Less than 10% change occurs during 4000 hours operation at 500 °C.
- Most silicon transistor specs sheets list larger parameter variations.
100 m
Current vs. Voltage Characteristics Key Parameters vs. Time @ 500 °C
NASA Glenn Discrete SiC JFET Transistors:
First to surpass 4000 hours of stable
electrical operation at 500 °C
0.0
0.2
0.4
0.6
0.8
1.0
0 10 20 30 40 50
Dra
in C
urre
nt (
mA
)
Drain Voltage (V)
Hours operating at 500 °C1st hour 100th hour4000th hour
0
2
4
6
8
0.0
0.5
1.0
1.5
2.0
0 1000 2000 3000 4000
I DSS
(m
A/m
m)
or |V
T+
10| (
V) g
m (mS/m
m) or R
DS (k
mm
)
Time (hours)
IDSS
gm R
DS
|VT + 10|
18
100 m
Demonstrates CRITICAL ability to interconnect transistors and other components (resistors) in a
small area on a single SiC chip to form useful integrated circuits that are durable at 500 °C.
Optical micrograph of demonstration
amplifier circuit before packaging
Gain vs. Frequency at 500 °C
2 transistors and 3
resistors integrated
into less than half a
square millimeter.
Less than 3% change in
operating
characteristics during
3000 hours of 500 °C
operation.
Inverting Amplifier
Differential Amplifier
Differential Amplifier
Inverting Amplifier
NASA Glenn SiC Amplifiers:
First semiconductor IC to surpass 3000
hours of electrical operation at 500 °C
0.6
0.81.0
3.0
101 102 103 104 105
Vol
tage
Gai
n
Frequency (Hz)
1 hour4000 hours
500 °C Test Time
-2
0
2
0.0 0.5 1.0
Sign
al (
V)
Time (msec)
T = 500 °C
Ouput1 hour4000 hours
1 kHz, 1VInput
1.0
10.0
101 102 103 104 105
Vol
tage
Gai
n
500 °C Test Time1 hour
3904 hours
-5
0
5
0.0 0.5 1.0
Sign
al (
V)
Time (msec)
1 kHz, 1VInput
Output1 hour3904 hours
T=500 °C
19
• Future work:
– Continuation of high temperature testing
– Continued improvement of fabrication procedures
– Fabrication of improved devices based on knowledgegained
• Long term goals:
– Technology transfer for SiC electronics work
– Complete integration of electronics and sensors fortotal harsh environment sensing capability
– Continue to push the envelope of what is possible inhigh temperature electronics and sensors, e.g., smartwireless sensor systems
Conclusion
20
Work is carried out at NASA GRC by:
• Glenn M. Beheim
• Carl W. Chang
• Liang-Yu Chen
• Gary W. Hunter
• Dorothy Lukco
• Philip G. Neudeck
• Robert S. Okojie
• David J. Spry
• Charles A. Blaha
• Robert Buttler
• Jose M. Gonzalez
• Kimala L. Laster
• Lawrence G. Matus
• Kelley M. Moses
• Michelle M. Mrdenovich
• Beth A. Osborn
• Andrew J. Trunek
Acknowledgments
21
The work in this talk has been supported by NASA’s Aeronautics
Research Mission Directorate:
• IVHM: Integrated Vehicle Health Management
• Supersonics
• Hypersonics
• Subsonic Fixed Wing
• Subsonic Rotary Wing
Recent press releases:
http://www.nasa.gov/centers/glenn/news/pressrel/2007/07-053_patents.html
http://www.nasa.gov/centers/glenn/news/pressrel/2007/07-035_Electric_Chip.html
NASA Funding