Time-Resolved Short Circuit Failure Analysis of SiC MOSFETs

Abstract

High-speed optical imaging is used in conjunction with fast electrical measurements to advance the understanding of the development of short circuit failures in silicon carbide power MOSFETs. Special samples are manufactured, which are compatible and comparable to TO-247 packages, but do not have any encapsulation. This allows optical observation of die surface during the test. The information on visible processes on the die allows for a better understanding of the sequence of events leading up to a failure. Imagery of destructive drain-source failures is also obtained, as well as post-failure images of surface and cross-sections. Aluminum metal melting is observed even for very short tests, before electrical indications of damage. The onset and completion of melting are used as information on the temperature of the die surface. Using this data for calibration, a detailed electro-thermal model is then used to simulate the temperature distribution and evolution during the short circuit.