Bias Temperature Instability and Junction Temperature Measurement Using Electrical Parameters in SiC Power MOSFETs

Junction temperature sensing is an integral part of both online and offline condition monitoring where direct access to the bare die surface is not available. Given a defined power input, the junction temperature enables the estimation of the junction-to-case thermal resistance, which is a key indicator of packaging failure mechanisms like solder voiding and cracks. The use of temperature sensitive electrical parameters (TSEPs) has widely been proposed as a means of junction temperature sensing; however, there are certain challenges regarding their use in SiC MOSFETs. Bias temperature instability (BTI) from charge trapping in the gate dielectric causes threshold voltage drift, which in SiC affects some of the key TSEPs including on-state resistance, body diode forward voltage as well as the current commutation rate. This article reviews the impact of BTI on the accurate junction temperature measurement using TSEPs in SiC MOSFETs.