Ohmic Contact And Bevel Edge Termination Study For 4H-SiC Reversely Switched Dynistor

Pulsed power switch is one of the core elements in pulsed power system,whose performance will determine the performance of the entire system.RSD?reversely switched dynistor?is a new type of semiconductor power devices which based on controlled pulse plasma trigger principle which has good voltage-sharing performance and high di/dt capability when compared to IGBT,SCR and other switching devices.RSD initially formed on silicon based semiconducting materials.The laboratory has come out of silicon carbide reversely switched dynistor?SiC RSD?due to the limitations of silicon-based devices which has higher breakdown voltage and lower switching loss when compared to Si RSD.This paper studies process parameter of each step?Lithography,Ion implantation,High temperature oxidation,High temperature annealing?and the complete manufacturing process of SiC RSD,which focuses on the key technologies of this device.Ohmic contact is an important process of SiC RSD.On SiC RSD device itself,anode side P⁺district and N⁺district are formed by ion implantation.Ion implantation involves etching,high temperature annealing,and these process will have indirect effects on ohmic contact characteristics.So this paper puts emphysis on the effect of sacrificial oxidation and high temperature annealing protection material SiO₂ respectively,which comes to a conclusion:The ohmic contact characteristics of SiC RSD can be improved through high temperature annealing protection material SiO₂,but on the basis,the improvement of the sacrificial oxidation process is not obvious.Specific contact resistance of P⁺and N⁺area are1.86E-4?·cm² and 4.8E-4?·cm² respectively.Suitable terminations can get better blocking properties.Because of the hardness of SiC and deep blocking junction of SiC RSD device,so this device adopts orthogonal positive-bevel termination.This paper does a research on mesa etching,thermal oxidation,PECVD SiO₂ and SiO₂ annealing by monitoring the leakage current and breakdown voltage which comes to a conclusion:550nm mesa etching,Thermal oxidation,PECVD SiO₂ can improve leakage current characteristics.SiO₂ annealing is of limited obvious significance.SiC RSD gains the breakdown voltage of 2820V by using positive bevel termination structure,74.1%of the simulation value.To SiC RSD,ohmic contact characteristics will directly influence turn-on voltage of the device,the terminal structure will directly affect the device blocking characteristics and pre-charge and the switching characteristics.Therefore,studies on SiC RSD ohmic contact and terminal structure are very important.