Device Research And Preparration Of 4H-SiC VDMOSFET

Silicon carbide?SiC?is particularly suitable for high-voltage,high-current power electronics due to its lager bandgap?3.26eV?,high breakdown electric field and great thermal conductivity.SiC metal-oxide-semiconductor field-effect transistor?SiC MOSFET?devices have broad application prospects in motors,automotive electronics and other industries beause of their higher reverse voltage,faster switching speeds and lower on-resistance.In foreign countries,the research level based on SiC materials and devices is higher,which realized commercial production and was forming an industrial chain.However,SiC MOSFETs are still in the research and development stage at domestic.This paper describes the structure design,key process development and device preparation of SiC MOSFET devices.The main contents are as follows:Based on the analysis of domestic and foreign 4H-SiC VDMOSFET devices,the key parameters and preparation process of 600V SiC VDMOSFET devices are determined.Firstly,Silvaco TCAD simulation software was used to simulate the ion implantation,the P-base region and N⁺implantation concentration and implantation depth of the device were simulated,all impurity distribution was realized by room temperature ion implantation.Secondly,the interface state of 4H-SiC MOS was studied by low-temperature PECVD post-oxidation annealing technique.The interface state density was calculated by high-frequency-low-frequency method and conductance method,and the interface state density of N₂O treatment was relatively low.The N-type and P-type ohmic contacts were studied,good N-type ohmic contact with a specific contact resistance of 5.01×10^-5?·cm² was ortained in room temperature N implantation.However,Ni metal and Ni/Ti/Al metal system P-type metal-semiconductor contacts with Ni and Ni/Ti/Al metal system were all schottky contacts and it is difficult to achieve good P-type ohmic contact at room temperature Al implantation.Through the development of the single-step process and the integration of these process,the preparation of the 600V 4H-SiC VDMOSFET device was completed experimentally and the corresponding electrical test was conducted.The device's threshold voltage is approximately 15V.The device's operating current is 700nA when V_GS=20V and V_DS=10V,which with the larger device's on-state resistance.Reverse leakage 3nA@600V and gate leakage 7pA@25V,the device's switching ratio is 10³.Based on infrared thermal analysis technology,when the reverse breakdown point of the device was tested,it was found that the breakdown of the device mainly occurred in the square cell region,and the square-cornered electric field was considered to be concentrated,which lead to device breakdown early,the sleek handing for cell edge is necessary in the future.