Figures-of-Merit Study for Thermal Transient Measurement of SiC MOSFETs

Thermal transient measurement (TTM) utilizes temperature-sensitive electrical parameters (TSEP) to analyze the thermal structure of power semiconductor devices. However, the measured physical quantities are essentially electrical parameters rather than direct temperatures. Determining whether these measurements reflect correct temperature or thermal structure of the tested device remains unclear. This limitation becomes more pronounced with emerging silicon carbide (SiC) devices. To address this issue, this paper provides a figures-of-merit (FOM) study for the TTM applied to SiC MOSFETs. The FOM comprises three static and two dynamic factors. The proposed FOM is employed to evaluate ten plausible testing circuits of a SiC MOSFET, where four of them are identified as providing reproducible thermal structures. A high-fidelity finite-volume method simulation is also used as a benchmark to validate the result. This study highlights some important facts, notably that successful TSEP calibration does not guarantee reproducible TTM, and compliance with current standards may also yield incorrect results. These insights hold significant implications for the field of SiC MOSFETs and the future development of the TTM method.