Research On New Structure Of SiC MOSFET With Integrated Low On-state Voltage Drop Diode

Silicon carbide metal-oxide-semiconductor field effect transistors（SiC MOSFETs）have advantages in high speed,high power,high operating temperature and high efficiency applications,and are gradually used in transportation,industrial control,energy transmission,military equipment and consumer electronics due to its excellent material characteristics.To improve the body diodes characteristics,short circuit capability and switching performance without increasing the cell width,three new structures of SiC MOSFETs with integrated low on-state voltage drop diodes are proposed.The main research contents are as follows:1.A double-channel planar gate SiC MOSFET（DCSD-MOSFET）with integrated Schottky barrier diode（SBD）and a triple-channel planar gate SiC MOSFET（TCSD-MOSFET）with split gate（SG）are proposed based on the conventional planar gate SiC MOSFET（Con-MOSFET）.SBDs are integrated at the sidewall of the source trench in both structures,which optimizes the diode conduction and reverse recovery characteristics.The two P+shield（P+S）and Pbody layers form additional junction field effect transistor（JFET）region,improving the short circuit capability.The P+S layers reduce the C_gd and improve the dynamic switching characteristics of the device.On the basis of DCSD-MOSFET,further optimization of the P+S layers and SG are adopted to obtain better switching and short circuit characteristics.The results show that the on-state voltage drop（V_F）of DCSD-MOSFET and TCSD-MOSFET are 1.67 V and 1.63 V respectively,which are 46.0%and 47.2%lower than the 3.09 V of Con-MOSFET.Compared with Con-MOSFET,the turn-on loss(E_on)is reduced by 23.3%and 62.9%,the turn-off loss(E_off)is reduced by 23.0%and 69.8%,and the short-circuit withstand time(t _SC)is increased by 1.1 times and 2 times respectively.2.A double trench SiC MOSFET with SG and integrated SBD（SGSD-DTMOS）is proposed on the basis of the conventional double trench SiC MOSFET（Con-DTMOS）,which features enhanced deep trenches in the surface.The deep trenches ensure enough Schottky contact area at the sidewall of source trench and source connected SG is adopted at the bottom of the gate trench,improving diode conduction,reverse recovery characteristics,C_gd and Q_gd of the device.The longer JFET region reduces the saturation current of the device.The results show that compared with Con-DTMOS,the V_Fof SGSD-DTMS is reduced by 52.8%,E_on and E_offare reduced by 56.4%and 70.4%respectively,and t _SC is increased by 7.5 times.