Research On Late-model SiC Power Diodes

Silicon carbide power diodes have maintained a significant market size in recent years,and the research of silicon carbide power diodes remains a heated topic.The most commonly used structure in the present power diode market is junction barrier Schottky(JBS)diodes.Silicon carbide JBS diodes have low forward voltage drop,high breakdown voltage,and excellent reverse recovery characteristics.The JBS diodes combine the advantages of PiN diodes and Schottky diodes.However,due to the limited doping depth of P-type impurity in silicon carbide material and the impact of the image force barrier reduction effect,the breakdown characteristics of JBS diodes are relatively soft,and the leakage current near breakdown is quite high.To solve this problem,this thesis proposes a silicon carbide sidewall enhanced trench junction barrier Schottky diode(SET-JBS).After comparing the simulation results,it is found that the maximum electric field density near the Schottky contact in the SET-JBS structure is only about one fifth of that in the JBS structure.Compared to the trench JBS structure(T-JBS)with similar effects,the specific on-resistance of the SET-JBS at the commonly used trench depth(about 2 μm)decreases by more than 21.6% compared to the T-JBS structure.This thesis also proposes a silicon carbide sidewall enhanced heterojunction diode(SET-HJD).After simulation research,it is found that the forward voltage drop of this SET-HJD can vary by about 0.2 V by changing the doping concentration in polysilicon.The breakdown voltage and current capability of actual silicon carbide power diodes are mostly improved by optimizing the blocking capability and efficiency of device junction termination.Based on the traditional field limit ring junction termination structure with uniformly increasing spacing,this thesis proposes three improved field limit ring structures,in which the third improved structure reduces the junction termination length by nearly 10 μm while reducing the maximum electric field density at the junction termination part.