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

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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