Design Of Silicon Carbide High Power Fast Ionization Device And Test Characterization Circuit

Fast ionization device(FID)is an all solid-state switching device which designed by the theory of ionizing waves.It can be quickly turned on in subnanosecond,and is widely used in pulser systems.At present,domestic research on fast ionization device is still at the stage of silicon material,low voltage and low pulse current.In recent years,due to the excellent characteristics of silicon carbide material,It has been widely used in the field of semiconductor devices,which has also made it possible to develop high power fast ionization device based on the silicon carbide.This thesis aims to design a silicon carbide high power fast ionization device.Firstly,the basic structure and working principle of FID are introduced,and a simulation platform based on Silvaco TCAD is build in this thesis.In the simulation of the cell of the device,according to the characteristics of the multi-layer PN junction structure of the FID and the limitations of the existing silicon carbide technology,the scheme of reversely extending the P~+NPN~+four layers on the N~+silicon carbide substrate is selected.And the doping concentration and thickness of each base region is determined according to the the breakvoltage,the pulse rising time,and the pulse peak current.In the design of the terminal structure,because the highest electric field of the silicon carbide FID is located at its internal PN junction when the device is in the blocking state,the conventional floating field ring terminal formed by the surface ion implantation has a lot limitations.The scheme of etched-step-type floating field limit ring terminal structure is selected in this thesis.Firstly,the P-type base region is etched away.Then the N-type base region is etched and the steps appear.Finally,the ion implantation is performed on the surface to form the field limit ring terminal structure.Subsequently,a pulse source circuit having multi-compression stages is developed to meet the working requirements of FID that require a pulse drive circuit.On the basis of the traditional pulse source circuit,a two-stage drift step recovery diode(DSRD)branch is added as the output sharpening stage,and the control method of the voltage of the capacitor in the circuit is improved from the difference of the two power supply voltage to a single supply voltage.These improvements narrow the rising edge of the output voltage pulse and make it easier to control the forward current of the DSRD branch.Based on the above pulse source circuit,the parameters of the silicon carbide FID are measured,such as the pulse rising time,pulse peak current,repetition frequency and the operating temperature.The results show that the breakvoltage is 6k V,the pulse peak current is 4.76k A,the pulse rising time is 1.4ns,the repetition frequency is500k Hz,and the operating temperature range is 25??100?,which basically meets the design indicators.