Silicon Carbide Bipolar Integrated Circuits for High Temperature Applications

Silicon carbide (SiC) is a semiconductor that provides significant advantages for high-power and high-temperature applications thanks to its wide bandgap, which is several times larger than silicon. The resulting high breakdown field, high thermal conductivity and high intrinsic temperature (well above 600 °C) allow high temperature operation of SiC devices and relaxed cooling requirements. In particular, SiC bipolar junction transistors (BJTs) are suitable for high temperature integrated circuits (ICs), due to the absence of a gate oxide. This work focuses on design, fabrication and characterization of the first 4H-SiC integrated circuits realized at KTH. It deals with basic bipolar ICs suitable for high temperature and low voltage applications. Operation up to 300 °C of low-voltage 4H-SiC NPN bipolar transistors and digital integrated circuits based on emitter coupled logic (ECL) has been demonstrated. In the temperature range 27 300 °C stable noise margins of about 1 V have been achieved for a 2-input OR-NOR gate operated on -15 V supply voltage, and an oscillation frequency of about 2 MHz has been observed for a 3-stage ring oscillator. The possibility of realizing PNP transistors and passive devices in the same process technology has also been investigated.