Analysis Of Dynamic Avalanche Of Semi-SJMOS

With the rapid development of electric vehicles,the application fields of SJMOS is f-urther broadened,but in practical application,it is necessary to study the dynamic avalanche of SJMOS because of the failure of dynamic avalanche caused by severe operation environment and excessive inductive load.In this paper,the mechanism of dynamic avalanche of SJMOS and SJMOS is studied by Sentaurus-TCAD simulator,the dynamic avalanche ruggedness of SJMOS and the influence factors the anti-dynamic avalanche ability of body diode are compared and analyzed,and two improved structures are proposed.The main contents of the study are as follows:Firstly,the dynamic avalanche effect and its mechanism of power MOSFET and body diode are briefly described.The structural parameters of 780V Semi-SJMOS are determined by simulation analysis and theoretical calculation.The influences of structural parameters and high temperature on the static and dynamic characteristics of Semi-SJMOS and the reverse recovery characteristics of body diode are discussed,and the key parameters are extracted.Secondly,based on the determined structural parameters,the structural model of Semi-SJMOS is established,the switching characteristics of Semi-SJMOS is simulated under unclamped inductive load,the occurrence mechanism and failure mode of Semi-SJMOS dynamic avalanche are studied.The influence of key parameters on the avalanche ruggedness of Semi-SJMOS is analyzed,and the measures to improve the avalanche ruggedness of Semi-SJMOS are pointed out.Thirdly,the reverse recovery characteristic of body diode under over-voltage is analyzed,and the occurrence mechanism and failure mode of dynamic avalanche during reverse recovery of body diode are studied.The influences of key structural parameters and temperature on the anti-dynamic avalanche ability of body diode are analyzed,and the measures to improve the anti-dynamic avalanche ability of body diode are pointed out.Lastly,two improved structures with a graded auxiliary layer and an npn auxiliary layer are proposed to improve the anti-dynamic avalanche ability of the body diode.The influence of the modified auxiliary layer on the dynamic avalanche ruggedness of Semi-SJMOS and the reverse recovery characteristics of the body diode are studied,the optimized structural parameters are extracted.