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