Short Circuit Capability and Short Circuit Induced VTH Instability of a 1.2-kV SiC Power MOSFET

The withstand capability and threshold voltage (VTH) instability of 1.2-kV silicon carbide (SiC) MOSFETs under repetitive short circuit (SC) tests are investigated. An SC test system is constructed to apply repetitive SC stress to SiC MOSFETs and measure the transfer I-V characteristics and gate-to-source leakage current (I-GSS) after each set of SC tests. To evaluate the SC capability, repetitive SC tests with different SC durations (t(p)) are conducted until device failure. The SC withstand time (SCWT) at 1000 SC cycles is found to be similar to 3.3 mu s. V-TH instability under repetitive SC tests prior to the device failure is characterized. A bidirectional V-TH shift behavior, i.e., negative shift at shorter t(p) and positive shift at longer t(p), was revealed. The V-TH shifts under repetitive SC tests are attributed to the SC pulse process according to the results of high-temperature reverse bias (HTRB) and dynamic high-temperature gate bias (HTGB) tests. The underlying mechanisms of the complex V-TH shift behavior are explained in a unified framework by taking into account the junction temperature (T-j) increase with longer t(p). TCAD device simulation is used to help analyze the mechanisms.