Reliability-Driven SiC Power Device Development for Army Applications

The Army is incorporating more and more electronic functionality into its vehicle platforms by converting many hydraulic functions to electronic to allow better power management, performance, and fuel efficiency. Because of high operating temperature (80 degrees-110 degrees C coolant), reliability, and efficiency requirements for these future power electronic systems, silicon carbide (SiC) technology has been under investigation by the Army since 1992. Since a recent demonstration by the Army Research Laboratory (ARL) of a 900-A power module implemented using 1200 V / 80 A SiC MOSFETs has confirmed SiC's high-temperature and high-efficiency advantage over silicon IGBT switches, the assessment of reliability and qualification of these SiC MOSFETs has become an imperative focus. Initial investigation of these large-area 80-A SiC MOSFET die shows that there is a threshold instability that is accelerated at junction temperatures of 150 degrees C and greater and may affect long-term reliability for 10,000-15,000 hr operation. Further, initial attempt at using Si industry reliability standards to qualify these SiC MOSFETs suggests that such standards may need to be modified.