Slide 1Team MembersTeam ResponsibilitiesOverviewKey SpecificationsSystem ComponentsUser InterfaceController BoardOriginal Design EquationsSimulated Resistance vs. TemperatureMeasured Resistance vs. TemperatureSiC SampleMicropipesDefect DensitySensor Cross-SectionFractional IonizationResistance ModelNew ModelR vs. T for n- layerR vs. T for p+ LayerModified Simulation ResultsCost AnalysisRe-Design / Future WorkAcknowledgmentsDemonstrationSlide 26Silicon CarbideTemperature Sensorfor Harsh EnvironmentsChris Rice Jason WallaceMichael Jackson Jovan BjelobrkADVISORDr. Stephen Saddow“a hot project…a cool advisor”Team MembersTeam ResponsibilitiesJovan BjelobrkJason WallaceMichael JacksonChris RiceSensor FabricationSensor TestingSensor FabricationSensor TestingSoftware InterfaceDevice ControllerPIC CodingDevice ModelingDevice Controller PIC CodingOverviewNo 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 $300System ComponentsTemp. SensorControllerCircuitSoftwareInterfaceUser InterfaceController BoardOriginal Design EquationsR = (L/A) = 1/(qnn)ni = sqrt(Nc*Nv)*exp(-Eg/2kT)n = (2.5*107)*T-2A = W*tSimulated Resistance vs. TemperatureTest Spec of 25 to 500 degrees C0 50 100 150 200 250 300 350 400 450 5000123456x 104Temperature [C]Resistance [Ohms]L (m) =100502010Measured Resistance vs. Temperature Resistance vs. Temperature01234567890 50 100 150Temp [deg. C]R (Kohms)10 500020 500050 5000100 500020 100050 1000100 1000SiC Sample20umMicropipesToday, 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, IncDefect Density1[cm]1[cm]Sensor Cross-Sectionp+ n-n+ n+IDepletionRegionFractional IonizationNa = 1E18 [cm-3]p = 10%(Na) = 1E17 [cm-3]p >> nR(p+) << R(n-)n = Nd = 5E15 [cm-3]Resistance ModelRn-Rp+Rn-: -- donor carriers fully ionized -- electron mobility controls R(n-)Rp+: -- acceptor carriers are NOT fully ionized -- hole mobility is dominated by the hole ionization(T) = 1/(qn(T)n(T))(T) = 1/(qp(T)p(T))R(T) = (T) (L/A)New ModelRn- = 1/(qnn) (L/A) Rp+ = 1/(qpp) (L/A) ni = sqrt(Nc*Nv)*exp(-Eg/2kT)A = W*tR = (Rn- * Rp+) / (Rn- + Rp+)R vs. T for n- layerR vs. T for p+ LayerModified Simulation ResultsL = 20um W = 5000 umCost Analysis~ $2000 per substrate (2 inch diameter wafer)~ $600 for whole-wafer EPI Growth~ $400 for Fabrication RunProducing 24 cells per wafer, and assuming overall yield of process of 72%, produces 120 usable devices at approximately $25 eachControl board components: $26.61Total cost for working unit: $51.61Re-Design / Future WorkDecrease the device area to minimize the chance of micropipe interference.Use an n-type substrate with a lower micropipe defect density.AcknowledgmentsDr. Stephen Saddow, EMRLDr. Jeff Casady, MCASPMr. Mike Smith, EMRLDr. Andrei Los, MCASPDemonstrationTemperature Center_beta4Silicon CarbideTemperature Sensorfor Harsh
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