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Silicon CarbideTemperature Sensor
for Harsh Environments
Chris Rice Jason Wallace
Michael Jackson Jovan Bjelobrk
ADVISOR
Dr. Stephen Saddow“a hot project…a cool advisor”
Team Members
Team Responsibilities
Jovan Bjelobrk
Jason Wallace
Michael Jackson
Chris Rice Sensor Fabrication
Sensor Testing
Sensor Fabrication
Sensor Testing
Software Interface
Device Controller
PIC Coding
Documentation
Device Controller
PIC Coding
Overview
No reliable way to detect temperature changes in extreme environments using typical semiconductor material (Si)Space travel involves extreme temperaturesSiC has the ability to operate in and withstand extreme temperatures (>500 °C)
Key Specifications
Increased Sensing Range 25 ° C to 500 ° C
Tolerance Temperature reading accuracy
of 0.5 °C at 25 °C
Cost Cost of working unit will be
less than $300
Timeline
February March April MayHardware Sensor Circuit Board
Software PIC Programming User Interface
Performance TestingTroubleshootingFinished Product
System Components
Temp. SensorController
CircuitSoftwareInterface
PCB LAYOUT
User Interface
Design Equations
R = (L/A)
= 1/(qnn)
Ni = sqrt(Nc*Nv)*exp(-Eg/2kT)
n = (2.5*107)*T-2
A = W*t
Resistance vs. Temperature
Test Spec of 25 to 500 degrees C
0 50 100 150 200 250 300 350 400 450 5000
1
2
3
4
5
6x 10
4
Temperature [C]
Res
ista
nce
[Ohm
s]L (m) =100
50
20
10
Measured Resistance V. Temperature SiC
Resistance vs. Temperature
0
1
2
3
4
5
6
7
8
9
0 50 100 150
Temp [deg. C]
R (
Ko
hm
s)
10 5000
20 5000
50 5000
100 5000
20 1000
50 1000
100 1000
SiC Sample
MicropipesToday, the density of micropipe defects in standard SiC commercial wafers, which are being used as substrates for SiC device fabrication, exceeds 100 cm-2. These micropipes, originated from SiC substrates, penetrate in device structures during epitaxial growth and cause the device failure
"Silicon Carbide Epitaxial Wafers",http://www.tdii.com/sic-g.htm,Copyright 1997, 1998 by TDI, Inc
Sensor Cross-Section
p+
n- n+ n+
I
Resistance Model
R(n-)
R(p+)
R(n-): -- donor carriers fully ionized -- electron mobility controls R(n-)
R(p+): -- acceptor carriers are NOT fully ionized -- hole mobility is dominated by the hole ionization
= 1/(qnn)
= 1/(qpp)
R = (L/A)
Fractional Ionization
Pd = 1E18 [cm-3]p = 10%(Pd) = 1E17 [cm-3]
p >> n
R(p+) << R(n-)
Calculations
Re-worked Simulated Results,These are being generated!!!
Cost Analysis~ $2000 per substrate (2 inch diameter wafer)
~ $600 for whole-wafer EPI Growth
~ $400 for Fabrication Run
Producing 24 cells per wafer, and assuming
overall yield of process of 72%, produces 120
usable devices at approximately $25 each
Control board components: $26.61
Total cost for working unit: $51.61
Silicon CarbideTemperature Sensor
for Harsh Environments