The Design Of 1200V 4H-SiC MOSFET

Under the background that the performance of silicon-based power switching devices is difficult to be greatly optimized,silicon carbide?SiC?materials have high thermal conductivity,fast electron saturation drift,high blocking voltage and strong anti-irradiation performance advantages,making SiC-based MOSFETs have broad application prospects in high temperature,high voltage,high speed and strong radiation field.Silicon carbide double trench MOSFETs?SiC DTMOS?have become one of the mainstream structure of SiC MOSFET design because of excellent performance advantages.Due to the problem of SiC MOSFET parasitic diode and its external anti-parallel diode,and considering the shortcomings of existing integrated Schottky barrier diode?SBD?technology,this paper develops the 1200V 4H-SiC DTMOS integrated SBD cell structure and terminal structure design,mainly includes:?1?Aiming at the shortcomings of the existing 4H-SiC MOSFET integrated SBD technology,a 4H-SiC DTMOS integrated SBD structure?4H-SiC SBD-DTMOS?is proposed.Based on the optimization of the main parameters of the integrated structure,including the thickness and concentration of the P2 region,the width of the plateau region and the depth of the gate trench,under the epitaxial layer parameters of 8?m thickness and 7.5e15 cm^-3 doping concentration,a structure with a breakdown greater than 1200V was obtained.The numerical simulation results show that the proposed 4H-SiC SBD-DTMOS has no influence on the basic performance of the the conventional silicon carbide double trench MOSFET device?4H-SiC CON-DTMOS?,including on-state,breakdown voltage and leakage,but significantly optimizes the body diode and switching performance of the device.In the static comparison of body diode,the diode of the 4H-SiC SBD-DTMOS device has a 50%lower turn-on voltage drop than the 4H-SiC CON-DTMOS body diode,the diode on-state voltage drop of 300A/cm² is reduced by 34%;In the dynamic comparison of body diode,the reverse recovery peak current decreased by 91.2%,the reverse recovery time decreased by 22.3%,and the reverse recovery charge decreased by 88.4%.While achieving a significant increase in the performance of the third quadrant,it maintains extremely low temperature leakage.Since the body diode has a critical impact on the turn-on process of the 4H-SiC MOSFET device,the optimized device has good electrical performance during the turn-on process,including 77.3%overshoot current drop ratio,66.01%recovery charge drop ratio,and 26.1%turn-on loss ratio.Finally,the influence of key parameters of the device on the performance of the device is also studied,for providing some reference for relevant designers.?2?The necessity of terminal structure design was verified,and terminal type selection was carried out at the same time.Taking into account the current state of the process of 4H-SiC SBD-DTMOS,the main parameters of the field limiting ring,including the number of rings,the ring width and the ring spacing,are carefully optimized to obtain a junction terminal with a voltage blocking capability of 1312V.The designed field limiting ring terminal has a good surface electric field distribution,a uniform ring partial voltage and an ideal breakdown point.On this basis,the process design and layout are completed.