Investigation on safe-operating-area degradation and failure modes of SiC MOSFETs under repetitive short-circuit conditions

The safe operating area is an operating area with high reliability for SiC MOSFET, and its degradation may cause power electronic system failure. The safe-operating-area degradation and the failure modes of 1200 V/66A SiC MOSFET caused by repetitive short-circuit stress with different short-circuit durations and repetition rates are investigated. A short circuit test platform with circuit protection is configured to degrade DUT(device under test), and the safe operating area is characterized after repetitive short circuit stress is applied. The degradation mechanism of the safe operating area is explained by the 1-D electro-thermal coupling model based on Sentaurus TCAD. When the critical short-circuit duration is 12μs, the single short-circuit failure mode of DUT with 400 V dc-bus voltage is a gate-source short-circuit failure. From the short circuit test result, the failure modes under repetitive short-circuit conditions include gate-source short-circuit failure and thermal runaway, depending on the repetitive rates. For the same short-circuit time interval, when the short-circuit duration is 10μs, the weakest boundary of the safe operating area is the blocking voltage. When the short-circuit duration is 2μs, all three boundaries of the safe operating area are contracted. These results are confined to 400 V dc-bus voltage, 25 °C case temperature, and 18 V/-3 V gate-source voltage.