Study On The Synergistic Effect Of Single Event And Displacement Damage In SiC MOSFET

In recent years,the third generation of wide band gap semiconductor materials with its excellent high-voltage,high frequency,high power density and other material characteristics,has been widely used in the field of semiconductor power device technology.SiC MOSFET is one of the representative devices.In the rapid development of aerospace and nuclear industry,SiC MOSFET will be more and more widely used in high-voltage and high-power applications,and the devices in the space radiation environment,will cause radiation damage to the devices or even failure,leading to the failure of the device function.Based on the above background,in this paper,the synergistic effect of single event and displacement damage on SiC MOSFET devices are studied,the ground test of heavy ion irradiation and neutron irradiation was carried out for SiC MOSFET.At the same time,the single event effect,displacement damage effect and synergistic effect of single event and displacement damage of SiC MOSFET were studied in combination with TCAD simulation,and the internal state changes of the device during irradiation were analyzed.The mechanism and law of radiation effect of devices are systematically discussed from the aspect of microscopic electrical parameters.The main research contents and work of this paper are summarized as follows:(1)We carry out heavy ion irradiation test and single particle effect simulation of SiC MOSFET.Irradiation test results show that when the selected SiC MOSFET are irradiated with ions of LET=75 MeV·cm2/mg,the two bias VGS and YDS are less than 300 V,the device only generates transient phenomenon.When VGS=0 V and VDS=400 V,SEB will appear.SEB occurs when VGS=-5 V and VDS=500 V.The TCAD simulation results show that the reason for the SEB of SiC MOSFET is the voltage difference generated by the transverse hole flow drift inside the device,which leads to the opening of the parasitic transistor.The positive feedback of the parasitic transistor makes the current density in the emission region(n=drift region)double,and the final device SEB occurs.At the same time,the positive feedback of the parasitic-transistor causes that the electric field intensity(3.2 MV/cm)at the interface of P+source/N-drift region is greater than the critical breakdown field strength(3 MV/cm)of SiC material.At the same time,the SEB rule of the device was explored,and it was found that when the simulation temperature was 225 K～300 K and the incident position was close to the P+source or below the gate.The higher LET value of the incident particle,the device would be more likely to SEB,and VGS had little influence on the SEB threshold voltage.(2)We carry out neutron irradiation experiment and simulation of displacement damage effect of SiC MOSFET.The radiation test results show that the saturation leakage current of the device decreases and the gate leakage current increases by comparing the electrical characteristics before and after neutron irradiation when the neutron fluence is 1×1014 n/cm-2.TCAD simulation results show that the threshold voltage of the device remains unchanged after neutron irradiation,mainly because the number of electron-hole pairs generated by neutrons in the channel is small and there is a high recombination rate,and the saturation leakage current of the device decreases.The reason is that the irradiation leads to the carrier being captured by the device displacement defect,which reduces the carrier concentration,mobility and lifetime of the device.The increase of subthreshold value is due to the trap charge leading to the formation of weak trans-layer state in advance,while the degradation of gate performance is due to F-N tunneling and defect assisted tunneling.(3)We carry out the simulation of SiC MOSFET single event and displacement damage synergistic effect.TCAD was used to construct a coincident effect model,and it was found that the center of the trap generated by the displacement damage defect captured the electron-hole pairs generated by the incident heavy ions,resulting in the decrease of the single event transient current in the device.At the same time,the SEB threshold voltage under different defect concentrations is simulated.When the SiC MOSFET LET=75 MeV·cm2/mg and VGS=0 V,when the electrical performance of the device is degraded due to displacement damage defects,the hardness of single event effect of the device is improved,which increases the threshold voltage of SEB from 510 V to 630 V.Finally,the law of the synergistic effect is explored,and the simulation shows that the synergistic effect is insensitive to bias voltage,while higher incident particle LET value will increase the sensitivity of synergistic effect.