Study On Radiation Neutron Damage Effects Of SiC Schottky Diodes And Field Effect Transistor

Silicon carbide（SiC）,as the third-generation wide bandgap semiconductor material,has the characteristics of wide band gap,high breakdown electric field,and high thermal conductivity.It is the key to the development of high-power,high-frequency,high-temperature,and strong radiation resistance technologies.During the operation of electronic devices in the space environment,they will be affected by space irradiated particles and rays,resulting in device performance degradation,thereby affecting the reliability of spacecraft in orbit.So far,there are few studies on neutron displacement damage of silicon carbide power devices,and the research objects are mainly focused on the description of the changes in electrical characteristics before and after irradiation.Based on the above background,this paper has carried out research on the damage effect of neutron irradiation displacement for silicon carbide Schottky diodes and field-effect transistors,using microscopic physical models to reveal the physical mechanism of neutron irradiation damage to silicon carbide devices,and in-depth through new characterization methods The changes of the internal parameters of the device before and after neutron irradiation are analyzed,and the damage mechanism of the neutron displacement damage effect on the silicon carbide device is explored.The main research content and structure of the thesis are:（1）Conducted neutron irradiation experiments of silicon carbide field effect transistors（MOSFET）,Schottky diodes（SBD）,and junction barrier Schottky diodes（JBS）.By comparing the electrical characteristics of the devices before and after irradiation,the results were obtained.The damage law of irradiation damage to silicon carbide devices.After neutron irradiation,the transconductance of the silicon carbide MOSFET device decreases,the saturation leakage current decreases,and the on-resistance increases.According to the MOSFET current calculation formula,neutron radiation displacement damage leads to a decrease in the effective doping concentration of the device and a decrease in channel carrier mobility.After neutron irradiation,the forward voltage drop of silicon carbide SBD and JBS devices increases,the reverse leakage current decreases,and the capacitance decreases.Neutron irradiation affects the Schottky contact at the metal/silicon carbide,increasing the Schottky barrier height,Which leads to the degradation of the electrical performance of the diode.（2）Irradiation experiments under different electrical stress conditions were carried out for silicon carbide MOSFET devices,and neutron irradiation experiments under different working conditions of MOSFET devices were set up.In the open state,the gate leakage current degradation is most obvious before and after the device is irradiated.According to the F-N tunneling mechanism,it can be known that when a voltage is applied to the gate,channel electrons tunnel into the oxide layer,and finally cause damage to the gate oxide layer.In the off-state state,the transconductance and saturation leakage current of the device degrade most obviously,which shows that under high field stress,not only electrons will be trapped by the device surface traps and material body traps,but also high-energy electrons trigger new defects in the device Traps further increase the density of traps and further enhance the degradation of device performance.（3）Two new characterization methods are used:1/f low-frequency noise measurement method and Deep Level Transient Spectrum Technology（DLTS）.After neutron irradiation,the noise of Si C MOSFET devices and SBD devices has increased.The reason for the increase of MOSFET noise devices is that the displacement damage effect of neutron irradiation has caused the interface defects（carbon vacancy defects）near the surface of Si C/Si O₂.The increase in noise of SBD devices is caused by the decrease of carrier mobility caused by the neutron radiation displacement damage effect.According to the DLTS test results of the JBS device,it is known that two defect energy levels are generated inside the device after neutron irradiation.The type and physical mechanism of each defect are determined according to the Arrhenius formula.