Research On Avalanche Tolerance Of SiC MOSFET

As a voltage-type control device,power MOSFETs have been widely used in power electronic switching circuits due to their high input impedance,fast switching speed,and no secondary breakdown.In recent years,with the development of wide bandgap semiconductor technology,silicon carbide(SiC)MOSFET power devices have been greatly developed,and mainstream semiconductor device manufacturers have basically introduced commercial SiC MOSFET series.Under such a trend that SiC power devices are gradually replacing Si devices,research on the reliability of SiC MOSFET devices is becoming increasingly important.For power MOSFETs,the main cause of failure in switch:ing circuits is avalanche breakdown.SiC has many excellent physical properties compared to Si,such as wide band gap,high thermal conductivity,high critical breakdown field strength,high carrier saturation speed,and the like.All of this makes SiC MOSFET power devices likely to exhibit different avalanche characteristics than Si MOSFETs.In the current SiC MOSFET datasheet,there is basically no avalanche tolerance test result,which is not conducive to the user's consideration and choice of avalanche tolerance.Therefore,in view of these current status and problems in the research of SiC MOSFET reliability,this article studies and discusses several issues of avalanche tolerance of SiC MOSFET,including the following,contents:With the non-destructive and destructive avalanche tests of CREE,ROHM,and ST's similar power SiC MOSFETs,this article compared and analyzed their differences in avalanche characteristics under the same test parameters,and attempted to explain the causes of the differences;at the same time,for the same type of SiC MOSFET,change the test inductance,charging voltage,charging time and other parameters,and then investigate the influence of different test parameters on the avalanche characteristics of the device under test,which provides a certain reference for the design of test condition of power SiC MOSFET in practical applications.In addition,this article attempts to summarize the normalization interval of avalanche voltage peak and avalanche current peak by testing the avalanche tolerance of different manufacturers'SiC MOSFETs with various voltage levels and current levels,thus providing reference for application and selection of power SiC MOSFET devices,in order to ensure cost savings under the premise of ensuring avalanche tolerance,and improve the cost performance of power electronics products.In the avalanche test of this article,some reliability problems were forund.-It mainly includes the high-frequency oscillation of the synchronization signal,the avalanche voltage and the avalanche current waveform,the reliability and accuracy of the avalanche current sampling,etc.The above problems were finally solved by replacing the test means,changing the sampling points and making signal isolation,thus ensuring the reliability of the avalanche test and the validity of the results.