Silicon Carbide Temperature Sensor for Harsh Environments

Silicon Carbide Temperature Sensor for Harsh Environments

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) • Problem detection = Problem prevention! Spacecraft problems have proven fatal

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

Team Responsibilities Chris Rice • Project Planning/Coordination • Sensor Design Jason Wallace • Documentation • Device Controller Design Michael Jackson • Documentation • Software/Web Design Jovan Bjelobrk • Fabrication • Sensor Design

Current Technology Limited Range Fragile Least sensitive Requires reference temperature • Thermistor Limited Range • Thermocouples Expensive (made from Pt) Self-Heating Less rugged than most High Initial Cost Accuracy affected by background radiation • Silicon Chips • Infrared Sensing • RTD (resistive temperature device)

Key Specifications • Increased Sensing Range • 0 ° C to 500 ° C • Increased Operation Range • 0 ° C to 1000 ° C • Increased Reliability • Performs equally well in temperature extremes without need for calibration

Si vs. SiC Comparison n/Nd = (Nd + ni) / Nd n/Nd ni = (NcNv)1/2exp[-Eg/2kT] OperatingRegion Si SiC 170 °C

Si Plot ofResistance vs. Temperature 1000μm L W L1 R=*L / A ; A=t*W L1 = 400 μm L=1200μm t = 500 μm W=3400μm

Prototype Layout Metal Contacts n+ or p+ n+ or p+ SI -SiC SI-SiC ~ 1x1015 -cm

SiC Preliminary Testing • Sample produced in EMRL • Applied voltage and measured current to determine resistance • Resistance obtained was too low • High resistivity sample needed!

System Components Vout • A/DConversion • SerialInterface • Temp. Display • Advanced Functions • Temp. Sensing • Voltage Output

Test Specification  * *      * * Denotes post-fabrication test

Cost Analysis • Approximately $2000 per substrate (35mm diameter wafer) • Approximately $600 for whole-wafer EPI Growth • Approximately $400 for Fabrication Run • Producing 25 devices per wafer, and assuming overall yield of process of 72%, produces 18 usable devices at approximately $167 each • Control board estimated at $30 • Total cost for working unit: $197

Device Implementation Control Board / PC Sensor

Future Integration • Incorporate onboard A/D as an integral part of the device design • Onboard calculation of actual temperature value • Design will be later incorporated into a single MEMS device for determining temperature, pressure, and vibration from a single point on a space vehicle

Silicon Carbide Temperature Sensor for Harsh Environments

Silicon Carbide Temperature Sensor for Harsh Environments