EXECUTIVE SUMMARYTo test the sample, it was wire-bonded in the EMRL laboratory. Wire bonding was performed using the EMRL wire-bonder at 180°C using gold wires. However, the approach of wire bonding will not provide the temperature durability necessary to meet the 1000°C upper limit of the operating temperature range. In order to meet the temperature requirement on a commercial production of the sensor, mechanical contacts composed of metals capable of withstanding 1000°C will used instead of wire-bonding.design document forTemperature SensorFabricated inSilicon Carbidesubmitted to:Professor Joseph PiconeECE 4522: Senior Design IIDepartment of Electrical and Computer EngineeringMississippi State UniversityMississippi State, Mississippi 39762May 1, 2001Submitted by:Team Leader: Jason WallaceTeam Members: Michael Jackson, Chris Rice, Jovan BjelobrkFaculty Advisor: Dr. Steve SaddowDepartment of Electrical and Computer EngineeringMississippi State Universityemail: {jdw2, mbj1, cdr1, jb2}@ece.msstate.eduSiC TEMPERATURE SENSOR Page 2 of 42EXECUTIVE SUMMARYThere is no reliable way, using the conventional semiconductor material (silicon), to detecttemperature in extreme environments. Silicon is well suited for a broad range of applicationswhen operating below 250°C. To keep silicon based microelectromechanical systems (MEMS)within their operating limits while allowing operation in high temperature environments can bespace and cost intensive, leading to impracticality for many applications [8]. In the area ofremote temperature sensing, most silicon based temperature sensors are rated by theirmanufacturer for temperature sensing ranges of 0 -150° C.This temperature sensor must be a small bolt on package capable of detecting temperatures up to500° C and physically withstanding temperatures in excess of the sensing range. To ensureaccurate measurements, the tolerance of the device should be within ± .5° C at 25° C. Forimplementation into both new and legacy systems the sensor module will operate over a voltagesupply range of +5V to +25V.As an alternative to silicon we will incorporate silicon carbide (SiC), a new semiconductortechnology being used in harsh environments. Research has shown that for a fixed maximaljunction temperature a SiC device can sustain about twice the power than a Si device [9]. Hightemperature operation, wide bandgap, and high electric field breakdown are some of thedesirable attributes that SiC possess [2]. First we will discover through our own testing thethermal characteristics of SiC as compared to Si. After which, we will implement a design tosense temperature and transmit acquired data via a RS-232 interface to a personal computerutilizing a graphical user interface system for the temperature display.By using silicon carbide, temperatures can be accurately sensed up to 500° C. This is a dramaticincrease of 333% above common rated silicon devices. Even though the sensor may not be ableto acquire exceptional temperature magnitudes in excess of 500° C, the device will physicallywithstand these environments without breakdown. In addition, the design of this sensor willintegrate analog to digital conversion in the microcontroller used for the serial interface therebyremoving the need for additional chips to perform this operation. This will reduce the cost andsize of the overall package, which will make it well suited for integration into applicationsrequiring multiple testing points. There will be an opportunity for further developments involving integration of this product withvarious other silicon carbide based sensors for other various applications. For example, otherdevices are being developed in conjunction this project that will sense vibration and pressure.The final goal of the entire project will be to use microelectromechanical systems (MEMS)technology to incorporate all three sensing devices onto the same silicon carbide chip. Thispresents the opportunity to test these related stresses from a single point source. An integratedmultiplexing device would allow for a single line acquisition of sensor data. This will providethe opportunity for monitoring of these stresses in harsh environments where sensor data can beused to trigger compensation systems in order to allow early prevention of possible problems.ECE 4512 May 1, 2001SiC TEMPERATURE SENSOR Page 3 of 42TABLE OF CONTENTSABSTRACT .................................................................................................. 51. INTRODUCTION............................................................................................ 52. PROBLEM .................................................................................................... 63. OBJECTIVES ............................................................................................... 73.1 Temperature Sensing Range...................................................................... 93.2 Ambient Operating Temperature ................................................................ 93.3 Tolerance .................................................................................................... 93.4 Self-Heating ............................................................................................... 93.5 Transient Response ................................................................................... 93.6 Reliability .................................................................................................... 93.7 Physical Packaging ....................................................................................103.8 Operating Voltage ......................................................................................103.9 Cost ............................................................................................................104. APPROACH ..................................................................................................10 4.1 Silicon Carbide Sensor ...............................................................................114.1.1 Geometric Parameters
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