Investigation On The Short-Circuit Failure Model Of SiC MOSFET

Compared to traditional silicon-based counterparts,power devices based on silicon carbide?SiC?,one of the third generation semiconductor materials,have superior performances,which has atttracted more and more concentrations from researchers.SiC MOSFET have the advantages of higher switching frequency,lower on-state resistance,higher breakdown voltage as well as better thermal conductivity.Therefore,SiC MOSFET have become the better choice in the power systems with higher requirements for converter efficiency and power density.With the further research on SiC MOSFET,in order to make better application of the device,it is necessary to establish a precise failure model which can accurately reflect the behavior of SiC MOSFET in circuit fault conditions.Firstly,this paper introduces the research background and status of SiC and MOSFET,secondly introduces the basic theory of traditional modeling for SiC MOSFET,and the main deficiencies and challenges it faces with have been pointed out.Based on hard switching fault,factors that contributes to the short-circuit ruggedness of SiC MOSFET have been fully analysed,which provides the basic theory for short-circuit failure modeling.With the strong ability of function processing for Matlab/simulink and its rich library blocks,the degradation mechanism of the channel mobility for the actual SiC MOSFET is considered,which can exactly reflect the effect of SiC/SiO₂ interface features on the characteristics of SiC MOSFET.Moreover,taking reliability issues on the gate dielectric into consideration that is related to the much thinner thinckness,the leakage current of SiC/SiO₂ system induced by carrier injection is implemented in Matlab/Simulink.To establish a strong foundation for the realization of device's failure model,the leakage current of P well/N-drift PN junction under high electric-field and temperature is also introduced.The proposed model is verified by the production datasheet and measurement data reported by other groups.Results show that the model is not only suitable for the simulation of the safe operation area,but also can accurately simulate the terminal electrical parameters caused by short-circuit failure.As for the activation of parasitic BJT for SiC MOSFET under short circuit fault condition,based on the basic theory of Bipolar Junction Transistor,the expression of current amplification coefficient for parasitic BJT under short-circuit condition is fully analyzed and modified,and the improvement measures to restrain the activation of BJT and enhance short-circuit robustness are proposed.The validity and feasibility of the method are verified by simulation results of TCAD two-dimensional physical model.The results are helpful for the practical application and protection of SiC MOSFET in power electronic circuits as well as the device technology.