| Owing to the wide band gap,high critical breakdown electric field,high thermal conductivity and high electron saturation drift velocity,Silicon Carbide can meet the needs of more harsh environment.With high power and low loss,4H-SiC MOSFETs are gradually used in photovoltaic system,new energy vehicles and locomotive traction and so on.In this thesis,thigh voltage 4H-SiC MOSFETs are investigated,including the optimization of device structures based on Atlas software,tape-out and experiment.The effects of Pbase doping profile,gate oxide thickness,channel length and the JFET region width on electrical characteristics is studied firstly.These structure parameters are optimized,and the structure of SiC MOSFET cell with breakdown voltage of 3000 V,threshold voltage of 2.9V,was obtained.Then,the terminal structure was investigated,including field plate and field limiting ring.The length of field plate and oxide thickness under field plate was discussed,which affects breakdown voltage and electric field distribution;For field limiting ring termination,the width and spacing of rings have an impact on breakdown voltage,so equally spaced ring structure and slowly varying spacing structure were studied.We simulated switching characteristics of SiC MOSFETs,including the influence of gate series resistance and load current.Finally,according to domestic Si C devices process platform,we designed the corresponding process flow,and conducted the work of tape-out and experiment.The experiment results of packaged SiC MOSFETs show the breakdown voltage reaches2500 V,on-state current is 2.4A and threshold voltage attains 2.3V.Besides,Dynamic characteristics test of SiC MOSFETs was carried out: Parasitic capacitances,switching characteristics,gate charge and the reverse recovery characteristic of body diode.The structure design,fabrication and the research of static and dynamic characteristics of 1700 V SiC MOSFETs provide consultation and support for the domestic high voltage SiC MOSFETs. |
PDF Full Text Request