The Study On Structural Optimization And Characteristic Test Of 4H-SiC RSD

Pulse power switch is an important component of the pulse power system,developing toward higher performance,and the reversely switched dynistor(RSD)is proposed and developed by Russian scientists.Compared with IGBT,SCR and other power devices,the device is characterized by high di/dt,low power loss and easy series and so on.With the appearance of the wide band gap semiconductor silicon carbide material,the characteristics of SiC material and the limitations of Si material have been considered.SiC RSD has the advantages of lower conduction loss,higher frequency characteristic and higher breakdown voltage compared with Si RSD.In this paper,the influence of the precharge time of SiC RSD on the opening characteristics is discussed.The influence of the device structure parameters on the opening characteristics is analyzed and the parameters are optimized by the orthogonal experimental design.The precharge avalanche tolerance and chip failure test of SiC RSD are studied.The studies are as follows:The effect of precharge time on the opening characteristics of SiC RSD under the same pre-charge is discussed by using the constructed two-dimensional model of RSD structure.The optimal precharge times of SiC RSD and Si RSD are respectively 0.25?s and 2.0?s,and the reason why the optimal precharge time of SiC RSD is better than that of Si RSD is analyzed.The influence of seven important structural parameters of 4kV SiC RSD on the opening characteristics of the device is studied.The orthogonal design method is used to optimize the seven important factors of the device,and a set of optimal parameter combination is get.Comparing the thermodynamic re-frequency characteristics of SiC RSD and Si RSD,the re-frequency characteristics of SiC RSD are better.The theoretical value of avalanche tolerance of SiC RSD is 3.16 J,and the operating range of safety precharge current of SiC RSD is obtained as follows: 9.08 A <Ipre <12.00 A,and the precharge current peak value of SiC RSD is 11.2A,and the precharge power consumption of SiC RSD is 0.00347 J.The forward and reverse characteristics of the SiC RSD chip after the pre-charge are failure,and the chip has a breakdown effect in the pre-charging process.The SiC RSD failure chip is investigated by FIB technique,PEM,SEM and TEM microscopys,and the cracks are observed at the breakdown point.It is observed that the SiC epitaxial layer has obviously crackes,which is the important reason for failure the chip occurred.