Design And Characteristics Of Ultra-high Voltage Silicon Carbide IGBT Device

Silicon carbide（Si C）insulated gate bipolar transistor（IGBT）shows wide application potential in the ultra-high voltage applications,i.e.,ultra-high voltage power transmission system.On one hand,Si C shows advantages on the bandgap,the critical breakdown electric field,the electron saturation drift velocity and thermal conductivity.On the other hand,IGBT shows high input impedance,ease of driving,high blocking voltage,and strong current transport capability.The current research of Si C IGBT mainly focuses on the trade-off between output characteristics and turn-off characteristics.This thesis is guided by the application requirements of Si C IGBT.In the thesis,not only the trade-off between output characteristics and turn-off characteristics,but the d V/dt controllability,electromagnetic interference（EMI）,short circuit characteristics and temperature characteristics are researched.Two new Si C IGBT structures based on the trench-gate structure and planar-gate structure are proposed.The main contents are as follows:1,the Adjustable P-Shield Potential IGBT（trench-gate structure）The special P-Shield can protect the bottom of gate oxide of the Adjustable P-Shield Potential IGBT（AP-IGBT）.Compared with the structures when P-Shield is grounded or floating,the gate oxide peak electric field of AP-IGBT lowers from2.7MV/cm and 6.5MV/cm to 1.4MV/cm,respectively.In addition,the modulation of P-Shield potential is realized by adjusting the deplation layer area under different operation state.P-Shield is floating under the on state and grounded under the blocking state.The output characteristics of AP-IGBT benefits from the floating P-Shield and the saturation current density is 20%lower than the structures when P-Shield is grounded or floating.Benefit from the lower doping concentration of P-Well1,the gate-collector charge(Q_gc)of AP-IGBT is 33%and 40%lower than the structures when P-Shield is grounded or floating,respectively.The turn-off energy(E_off)of AP-IGBT is 56%and62%lower than the structures when P-Shield is grounded or floating,respectively.The d V/dt controllability of AP-IGBT is 10%and 56%lower than the structures when P-Shield is grounded or floating,respectively.The EMI characteristics of AP-IGBT(d V/dt when E_on=1550m J/cm~2)are 17%and 35%lower than the structures when P-Shield is grounded or floating,respectively.Otherwise,the short circuit time of AP-IGBT is 97%and 37%longer than the structures when P-Shield is grounded or floating,respectively.2,the Emitter Schottky Contact IGBT（planar-gate structure）The gate oxide peak electric field of the Emitter Schottky Contact IGBT（ESC-IGBT）lowers from 2.4MV/cm to 1.3MV/cm.Meanwhile,the Schottky junction in the blocked state is protected by the P-Well,which lowers the leakage current of Schottky junction.In the on state,the charge storage layer（CSL）suppresses hole transportation.Therefore,the output characteristics of ESC-IGBT are not significantly degraded compared to the conventional structure.Otherwise,part of Q_gc turns into the gate-emitter charge(Q_ge),so the Q_gc of ESC-IGBT is 37%lower than the conventional structure.Meanwhile,the E_off of ESC-IGBT is 34%lower than the conventional structure.The d V/dt controllability of ESC-IGBT is also slightly better than the conventional structure.In the turn-on stage,the Schottky junction helps extract the nearby hole,so the EMI characteristics of ESC-IGBT improve 10%(d V/dt when E_on=400m J/cm~2).