Accurate Temperature Estimation of SiC Power MOSFETs Under Extreme Operating Conditions

摘要

Electrothermal modeling of silicon carbide (SiC) power devices is frequently performed to estimate the device temperature in operation, typically assuming a constant thermal conductivity and/or heat capacity of the SiC material. Whether and by how much the accuracy of the resulting device temperature prediction under these assumptions is compromised has not been investigated so far. Focusing on high-temperature operating conditions as found under short circuit (SC), this paper presents a comprehensive analysis of thermal material properties determining the temperature distribution inside SiC power MOSFETs. Using a calibrated technology computer-aided design (TCAD) electrothermal model, it is demonstrated that the temperature prediction of SiC power devices under SC operation when neglecting either the top metallization or the temperature dependence of the heat capacity is inaccurate by as high as 25%. The presented analysis enables to optimize compact electrothermal models in terms of accuracy and computational time, which can be used to assess the maximum temperature of SiC power MOSFETs in both discrete packages and multichip power modules exposed to fast thermal transients. A one-dimensional thermal network of a SiC power MOSFET is proposed based on the thermal material properties, the size of the active area of the device, and its thickness.