Download or read book Fabrication and Characterization of 4h-sic Jfet-based Integrated Circuits written by Srihari Rajgopal and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation demonstrates 4H-SiC integrated circuits (ICs) operating to 500 deg.C (932 deg.F), using 10 μm, n-channel depletion mode junction field-effect transistors (JFETs). Key challenges in this development included: (i) large variations in the doping level and thickness of the SiC epitaxial layers of the starting wafers; (ii) low hole mobility of n-type 4H-SiC; (iii) limited circuit design space due to the use of only n-type devices and resistors; (iv) large variations in device parameters from room temperature to 500 deg.C; and (v) fabrication processes limitations.A number of analog IC building blocks for sensor interfacing and signal conditioning were included in the development effort, including a voltage reference, an instrumentation amplifer (INA) with a buffer amplifier to (i) regulate power supply voltage, and (ii) amplify and buffer the output of a low frequency voltage-based bridge-type pressure sensor.An outline of the contributions of this work is as follows:1. 4H-SiC, JFET-based sensor interface ICs were fabricated and could operate from room temperature to 500 deg.C.2. A voltage reference building block was demonstrated, with line regulation of ±2.5% between 25V to 50V input voltage from 100 deg.C to 500 deg.C using a 5.95 kO external resistor load. Load regulation was within ±3.5% between 25V to 50V input voltage from 100 deg.C to 500 deg.C with load resistances of 4.99 kO to 7 kO.3. An INA was implemented as a cascaded connection of front- and back-end units. The back-end amplifier demonstrated a differential gain of 17 dB, dropping to 14.2 dB from 25 deg.C to 500 deg.C. The frequency response of the buffer amplifier was stable between 25 deg.C to 500 deg.C--with a 3 km-long cable load representative of down-hole drilling applications.4. Material and fabrication issues that resulted in the deviation of the resistor values and transistor threshold voltages from intended design values were identified using a combination of materials analysis, transistor parametric modeling, circuit simulation and test bench measurements.5. An investigation into alternative high-temperature dielectric materials was also initiated. Both aluminum oxide and hafnium oxide appear promising for future designs, though further tests are needed.In high temperature sensor interface applications, JFET 4H-SiC IC technology is shown to be viable.