Mechanism of Maximum-Current Limitation for 10-kV SiC-IGBT Module by Analyzing Surge Current Test Result

To develop a high-power and small-size pulse power source, the mechanism of maximum-current limitation for a 10-kV silicon carbide (SiC)-insulated-gate bipolar transistor (IGBT) device during a millisecond-short pulse was investigated. One method of measuring the maximum current is the surge current test. Although some of a Si-IGBT module’s surge current capability was reported, there have been no reports for a SiC-IGBT module. We fabricated a single-chip 10-kV SiC-IGBT module consisting of our 10-kV SiC-IGBT chip and conducted a surge current test using the module. After the test, the module failed by a short between its collector and emitter. From the results of the failed chip observation and thermal simulation, we concluded that the cause of failure was the melting of the aluminum electrode or bonded wires on the SiC-IGBT device, which was caused by the increasing temperature on the top side of the device. The estimated current limit calculated by the equation of semiconductor theory was almost consistent with the surge current test result. The determined parameter for the current limit was the bulk mobility of the SiC device, which decreases with increasing temperature. To suppress the increasing temperature on the surface of the SiC-IGBT device, a structure of the module with a Cu plate added on the top side of the device was simulated. The simulated result indicated that the structure can decrease the temperature on the surface of the device and increase the current limit.