Electrothermal Power Cycling to Failure of Discrete Planar, Symmetrical Double-Trench and Asymmetrical Trench SiC MOSFETs

While SiC MOSFETs are now being utilized in industry their robustness under heavy-duty applications still remains a concern. In this paper, the results of experimental measurements of degradation to failure of different structured SiC power MOSFETs, namely the planar, symmetrical double-trench and asymmetrical trench structures are presented following electrothermal stressing by power cycling to beyond the safe operating area (SOA) limits. The tests are categorised in to subsets with/without forced cooling. The first set of tests involve successive switchings of the devices under constant DC current supply while their case temperature is monitored in real-time to evaluate their thermal performance. The symmetrical double-trench and asymmetrical trench MOSFETs are found to experience a higher case temperature rise thus prone to breakdown while failure is not observed in the planar structured device. The second experiment stresses the devices during continuous power cyclings with force cooling applied, in which the symmetrical and asymmetrical double-trench MOSFETs still encounter failure with detectable breakdown on the gate oxides, compared with the planar device which only exhibits degradation, without failure, with indications of aging

SiC power MOSFETs performance, robustness and technology maturity

Relatively recently, SiC power MOSFETs have transitioned from being a research exercise to becoming an industrial reality. The potential benefits that can be drawn from this technology in the electrical energy conversion domain have been amply discussed and partly demonstrated. Before their widespread use in the field, the transistors need to be thoroughly investigated and later validated for robustness and longer term stability and reliability. This paper proposes a review of commercial SiC power MOSFETs state-of-the-art characteristics and discusses trends and needs for further technology improvements, as well as device design and engineering advancements to meet the increasing demands of power electronics