Reliability and Condition Monitoring of SiC Power MOSFETs




Journal Title

Journal ISSN

Volume Title



As electrical devices are becoming an indispensable part of our lives and pretty much of all industries, efficient and reliable operation of power converters which energize these devices is also becoming crucial. Todays modern power converters commonly utilize silicon (Si) semiconductor devices to perform high speed switching operation, and therefore their performance is limited by the material properties of Si. The latest potent alternative semiconductor technology for high voltage and high temperature applications is silicon carbide (SiC) due to their higher voltage ratings, higher maximum operating temperatures, and higher thermal conductivity. Although SiC devices provide a solution to overcome the physical limitations of Si, their market adoption remains limited. Reliability of SiC devices is one of the main barriers preventing their high penetration into the market. Therefore, it is essential to investigate progressive degradation and parameter shifts in SiC devices to develop condition monitoring tools which can recognize failure precursors at the earliest stage and increase the system reliability. This dissertation presents a comprehensive long-term reliability analysis of commercially available SiC MOSFETs under high temperature operation. For this purpose, discrete SiC devices are power cycled and variation of electrical parameters throughout the aging is presented in order to assess the key precursor parameters and their correlation with the state of device aging. Discussions regarding aging precursors are supported by detailed failure analysis. It has been revealed that the most popular precursor parameter, on-state resistance, reveals the combination of gate oxide and packaging related degradation while threshold voltage mainly depicts gate oxide related issues. Unlike these two parameters, the body diode voltage drop is found to be independently indicating device state of health (SOH) both for packaging and gate oxide degradation. Based on this finding a new condition monitoring method is proposed for SiC MOSFETs which deploys reverse body diode voltage drop at different gate bias levels. The proposed condition monitoring method is implemented on a gate driver circuit and experimental results are presented. The proposed method can be integrated into a gate driver or can be implemented at converter level to monitor the SOH of devices.



Silicon carbide, Metal oxide semiconductor field-effect transistors, Structural health monitoring


©2019 Enes Ugur. All rights reserved.