Research On New Superjunction VDMOS With Low Reverse Recovery Charge

With the development of power semiconductor technology,super-junction VDMOS has a very broad prospect in switching power supply field because of its low conduction resistance,high switching speed and high switching frequency.However,there are internal parasitic body diodes with large junction area in the drift region,which will cause a large energy loss in the reverse recovery process.To solve this problem,it is necessary to research the reverse recovery characteristics of super-junction VDMOS.This research summarized the development of the super-junction VDMOS,explained the basic theory of super-junction VDMOS and body diode reverse recovery from the theoretical level.Then,the research simulated and analyzed the relationship between the doping concentration in different regions of super-junction VDMOS and the reverse recovery characteristics,such as N+-sub,n-pillar,P-body,etc.Simulation results showed that doping concentrations and the widths of the P-pillar and the N-pillar had great influence on the reverse recovery characteristics.Furthermore,the wider N-pillar and the narrower P-pillar were help to reduce the reverse recovery effect.In order to meet the demand,we proposed a double-channel super-junction VDMOS to improve the reverse recovery.The new double-channel structure establish the new source in the region of the grid and JFET above,at the same time,N-pillar,P-body and N+source respectively were established on the conventional JFET,the new source and the newly established area formed two MOS structure.By controlling the silicon dioxide thickness in the contact area,the MOS threshold voltage is lower than the conducting voltage of the conventional PN junction which form MOS takes the lead in body diode conduction,it reduced the N-pillar areas of electronic injection into P-pillar areas and it changing the electron hole concentration in the n-pillar drift region of the inverse conduction phase.Compared with the conventional super-junction VDMOS,the reverse recovery performance of the double-channel structure can be improved about 26%.At the same time,the newly added region and the gate form two positive conduction which optimizes the saturation current characteristics of the double-channel structure.