1. Silicon Carbide
Temperature Sensor
for
Harsh Environments

2. Team Members ADVISOR Chris Rice Jason Wallace Dr. Stephen Saddow
“a hot project…a cool advisor”
Michael Jackson
Jovan Bjelobrk

3. Team Responsibilities
Chris Rice
Sensor Fabrication
Sensor Testing
Jason Wallace
Documentation
Device Controller
PIC Coding
Software Interface
Device Controller
PIC Coding
Michael Jackson
Sensor Fabrication
Sensor Testing
Jovan Bjelobrk

4. Overview
No reliable way to detect temperature changes in extreme environments using typical semiconductor material (Si)
Space travel involves extreme temperatures
SiC has the ability to operate in and withstand extreme temperatures (>500 °C)

5. 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

6. Timeline

7. System Components
Controller
Circuit
Software
Interface
Temp. Sensor

8. PCB LAYOUT

9. User Interface

10. Design Equations R =  (L/A)  = 1/(qnn)
Ni = sqrt(Nc*Nv)*exp(-Eg/2kT)
n = (2.5*107)*T-2
A = W*t

11. Resistance vs. Temperature
L (mm) =100 50 20 10
Test Spec of 25 to 500 degrees C

12. Measured Resistance V. Temperature SiC

13. SiC Sample

14. Micropipes
Today, 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", 1997, 1998 by TDI, Inc

15. Sensor Cross-Section
n n+ n- I p+

16. Resistance Model  = 1/(qnn) R =  (L/A)  = 1/(qpp)
R(n-): donor carriers fully ionized
-- electron mobility controls R(n-)
R(n-)
 = 1/(qnn)
R(p+)
R(p+): acceptor carriers are NOT fully ionized
-- hole mobility is dominated by the hole
ionization
R =  (L/A)
 = 1/(qpp)

17. Fractional Ionization
Pd = 1E18 [cm-3]
p = 10%(Pd) = 1E17 [cm-3]
p >> n
R(p+) << R(n-)

18. Calculations
Re-worked Simulated Results, These are being generated!!!

19. 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

20. Silicon Carbide
Temperature Sensor
for
Harsh Environments