Evaluation of the Long Term Reliability and Failure Modes for Silicon Carbide High Power Semiconductor Devices

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2017-05

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Abstract

Advancements in the design and fabrication of power semiconductor devices have led to increases in their power density, but fundamental limits are being reached due to inherent properties of silicon. Wide bandgap semiconductor technologies are a strong alternative to silicon for advancing the power density limits of high power devices. Silicon carbide (SiC), specifically, is being developed for power electronics and pulsed power applications because of its inherent properties that allow higher temperature operation and smaller footprint devices for the same voltage and current capabilities power semiconductor devices made of silicon currently offer. Evaluating the capability and long term reliability of SiC power semiconductor device technology is pertinent before operation in real-world applications is achievable. This thesis summarizes the evaluation of research grade SiC PiN diodes rated for 15 kV and 46 A continuous with an active area of 0.465 cm2 and SiC IGBTs rated for 15 kV and 32 A continuous with an active area of 0.32 cm2. The SiC PiN diodes were evaluated in a long term reliability test bed with 100 µs pulses of 1.5 kA to 2.5 kA at 0.5 Hz. Testing revealed long term reliability (over 100,000 pulses) at 1.5 kA. Instability in the forward voltage drop on the PiN diodes occurred over the first thousands of pulses throughout testing. Electrical degradation of the PiN diodes included an increase in on-state voltage and an increase in reverse leakage current. Physical degradation of the PiN diodes included bonding wire liftoff and surface burning and cracking. The SiC IGBTs were evaluated in a narrow pulse RLC ring down test bed with 2 µs pulses of 55 A to 95 A at 1 Hz. Testing has revealed long term reliability (over 100,000 pulses) in this current regime. No degradation has occurred during testing of the IGBTs.

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Keywords

silicon carbide, power semiconductor devices, PiN diode, pulsed power, insulated-gate bipolar transistors (IGBTs)

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