Research On Single Event Effect On SiC Junction Barrier Schottky Diode For Aerospace

Silicon Carbide?SiC?,the third generation semiconductor,has excellent material properties such as wide band gap,high critical electric field,high thermal conductivity,etc.SiC power devices have advantages of high temperature and high voltage,low self power consumption,etc.SiC power devices become a new generation of spacecraft key components selected for power supply,electric propulsion and other systems.Single Event Effect?SEE?hardness of SiC Junction Barrier Schottky Diode?JBS Diode?is far less than expected,and leakage degradation or even Single Event Burnout?SEB?occurs when the bias voltage is much lower than the rated voltage,which cannot meet the needs of aerospace applications.At present,it is not yet clear about the mechanism of SEE,the differences in the radiation hardness of devices with different process structures and the influencing factors of SEE,resulting in a lack of basis for the development of SiC JBS diodes SEE evaluation method,selection for use,radiation and application reinforcement.For these problems,the research contents and innovations are as follows:1)The failure mode of the SiC JBS diode was verified.By performing SEE experiments under different irradiation conditions,it was verified that there were two modes of SEE failure in SiC JBS diodes:leakage degradation and SEB.2)Based on the combination of EMMI,DLTS defect analysis technology,heavy ion microbeam/wide beam irradiation test and TCAD simulation,the models of leakage degradation and SEB were supplemented and improved.By performing the heavy ion micro-beam test,the"micro-SEB"theory was verified,and it was found that the leakage current increased with fluence as a result of multiple ions acting separately.The increasement in leakage current of the SiC JBS diode has a cumulative effect.Combined with the EMMI observation,electrical characteristics comparison and DLTS analysis of the leakage degradation sample irradiated,it was believed that the leakage degradation of the SiC diode was caused by the incident ions generating defects inside the semiconductor to form micro damage,which changed the electric field distribution at Schottky contact.As a result of Schottky barrier height reduction and trap-assisted tunneling effect,the leakage of SiC diode degraded.Based on the heavy ion irradiation test and TCAD device simulation results,it was believed that SEB was caused by the incident ion causing the local electric field of the SiC JBS diode to reach the avalanche breakdown voltage and avalanche breakdown occurred.3)The influence of the device structure on SEE was studied,and the device reinforcement measures and selection suggestions were proposed.The effect of device structure on SEE was studied through heavy ion irradiation experiment.It was analysied that the honeycomb structure was more susceptible to SEE.A composite terminal structure might be considered to improve the reliability and stability of the device breakdown voltage.On the basis of satisfying the conventional characteristics such as breakdown voltage and on-resistance,choosing the strip structure was more conducive to improving the ability of the radiation hardness of the device.4)The effects of different test conditions on SEE were studied.By controlling variables such as bias voltage and incident ion LET,experiments were conducted to study the effects of different factors on SEE.The results showed that the higher the applied bias voltage,the easier SEE occurred;the higher the incident ion LET,the easier SEE occurred.Leakage was positively correlated with fluence accumulation.TCAD simulation verified the influence of the bias voltage and the incident ion LET,and also obtained the results:particles incident from the Schottky or PN junction had little impact on the occurrence of SEE,and were related to the damage location;normal incidence was the worst condition.5)Proton SEE was studied.High-energy proton irradiation tests were carried out on 1200V SiC JBS diodes with different structures.The cumulative fluence reached5×10¹⁰ cm^-2.It was shown that the leakage current decreased with the increasement of fluence,and there was no SEB.The reason for the decrease in leakage current was related to the annealing effect and the increase in Schottky barrier height.SiC JBS diodes were resistant to proton SEE.6)The effect of current limiting on the SEE of SiC devices was studied.The effectiveness of two reinforcement measures,i.e.power over-current protection and current limiting with series resistance,was studied.Under the current limiting condition of 100?A/10mA power supply in ground test system,SEB occurred.While under connecting 0 k?,30 k?,and 620 k?resistors in the radiation test circuit,it was shown that the greater the current-limiting resistance was,the smaller the degradation of the reverse characteristics of the device was.Combined with TCAD simulation results,the reason why the ground test system power supply current limiting has no protection on SEB was that the response time was too long?ms?.