Design And Experimental Investigation Of Ultra High Voltage Silicon Carbide JBS Diode

Silicon carbide,a typical third generation semiconductor,has many excellent physical properties,such as wide band gap,high critical breakdown electric field,high thermal conductivity,high saturated electron velocity,anti-irradiation and so on,which makes silicon carbide devices have a good development prospect.SiC JBS diodes have the advantages of low forward opening voltage,large reverse blocking voltage and fast turn-off,so they are being used in power electronic equipment such as new energy vehicles and charging piles.In addition,SiC JBS diodes have good temperature characteristics.When the temperature increases,the forward threshold voltage decreases,the forward on-resistance increases,and the current capacity decreases.Therefore,the SiC JBS diode can be used in parallel without the effect of current concentration.At present,there are few researches on UHV SiC JBS diodes in China,and the research level lags far behind the foreign countries.In this paper,the UHV 4H-SiC JBS diodes are studied.The SiC JBS diodes with different structures are designed.The tape-out and test are carried out in the Institute of Microelectronics of the Chinese Academy of Sciences.The aim is to provide reference for the design and fabrication of UHV 4H-SiC JBS diodes in China.The research content of this paper is divided into three parts.Firstly,SiC JBS UHV diodes with breakdown voltage over 10kV are designed by Silvaco Atlas semiconductor simulation tool.For the drift region with doping concentration of 5×10¹⁴cm^-3 and thickness of 100?m,the effects of two adjacent P⁺spacing in the active region on the forward conduction current and the reverse leakage current are simulated.The results show that with the increase of the proportion of Schottky contact,the forward conduction current and the reverse leakage current increases.The field limiting rings of uniform ring spacing and slowly varying ring spacing are analyzed in this paper.The results show that the efficiency of uniform ring spacing is low,while the slowly varying ring spacing keeps the characteristics of simple design of uniform ring spacing and high terminal efficiency.This paper also introduces the charge distribution of conventional JTE and modified JTE,and describes the structural characteristics of field limiting rings with slowly varying ring spacing from the angle of charge distribution.Secondly,many experiments are carried out to improve the Schottky barrier heigh between Ni and SiC.In the experiment,the samples are divided into two groups.One group keeps the annealing time constant and changes the annealing temperature.The other group keeps the annealing temperature constant and changes the annealing time.The annealed samples show that the maximum Schottky barrier height is 1.72eV.Finally,the process of UHV 4H-SiC JBS diode is implemented.The tape-out experiment and test analysis are also carried out.The experimental results show that the maximum reverse breakdown voltage is 14kV.The efficiency of termination reached99%.