Research And Optimization Of Reverse-revery Robutness For Super-junction VDMOS Body Diode

Superjunction Vertical-Diffused Metal-Oxide-Semiconductor Field-Effect Transistor has low on-resistance,fast switching speed,and has a good application prospects in the field of power electronics which is represented by electric vehicle charging pile.The bridge-type inverter circuit used in electric vehicle charging piles requires that the Superjunction-VDMOS device has very high reverse-recovery robustness of body diode.At present,the research on the reverse recovery of Superjunction-VDMOS body diode is mainly focused on the driving circuit level to improve the reverse recovery characteristics,there is little research on improving the reverse-recovery robustness of Superjunction-VDMOS body diode itself.Therefore,it is of great significance to study and improve the reverse recovery robustness of Superjunction-VDMOS body diode.A test and simulation platform based on the basic theory of reverse recovery of Superjunction-VDMOS body diode are built in this thesis.The current change rate di/dt in the reverse recovery process is the main factor which affects the reverse recovery failure of Superjunction-VDMOS body diode are shown in the measured results and the failure points of the is located in the terminal area.The excess carrier velocity in the cell region is much higher than that in the terminal region during the process of reverse recovery of the Superjunction-VDMOS body diode is shown in simulation results,the current peak appears in the terminal region,resulting in an increase in the surface electric field and a dynamic avalanche,and the greater the di/dt,the more serious the dynamic avalanche.A dynamic field limiting ring termination structure is proposed in this thesis which can suppress the peak electric field during the process of body diode reverse recovery,the dynamic avalaches are suppressed and the reverse recovery robustness of body diode is improved on the basis of ensuring the performance of other parameters of the Superjunction-VDMOS.Based on the 650V deep trench etching process,In the measured results,the Superjunction-VDMOS body diode reverse recovery limit di/dt capacity is improved from 72A/?s to 320A/?s on the basis of guaranteeing other parameters,the body diode reverse-recovery robustness is increased by 3.2 times which has met the design requirements.