Research On Reliability Test And Evaluation Of 4H-SiC JBS Diode

SiC material has become the materials of choice for high-performance modules due to their wide band gaps,high thermal conductivity,and high breakdown field strength.Among them,SiC JBS diode combines the advantages of high voltage resistance and fast switching speed of SBD diode,small reverse leakage current of Pi N diode.They are widely used as rectification and freewheeling components in aerospace,high-frequency rectification,switching power supplies and protection circuits.Therefore,the application environment of high temperature,high voltage,high humidity and high current puts forward more severe requirements for the reliability of SiC JBS diode.Based on the reliability of 4H-SiC JBS diode in the above application environment,this paper conducts theoretical and experimental research,and analyzes and extracts sensitive parameters to characterize device reliability.First,the electrical characteristics and 1/f noise characteristics of SiC JBS diodes were tested under stress conditions of 175℃,960 V reverse bias,and 168 hours,and the degradation mechanism of the device under high temperature reverse bias was analyzed.After the high temperature reverse bias test,the reverse leakage current of the SiC JBS device increased from 31.044 nA to 2150.39 nA,increased by 2120 nA,the breakdown voltage decreased by 122 V,and the noise amplitude increased by 1E-13V2/Hz.After analysis,under high temperature reverse bias,the barrier height caused by the mirror image force and the tunneling effect is significantly reduced,which will cause the leakage current to increase sharply and the withstand voltage to decrease;On the other hand,the electron tunneling fluctuation caused by the increase of interface defect density under reverse bias leads to the increase of JBS noise.By analyzing and comparing the change rate of the parameters,the reverse leak current IR change rate reaches 6800%,compared to the forward voltage drop VF,reverse breakdown voltage VBD,and noise amplitude B parameters,which are all below 50%,with significant advantages.Therefore,the leakage current IR is selected as a characterization parameter to more sensitively characterize the high temperature reverse bias damage of SiC JBS device.Then,in this paper,the electrical characteristics and 1/f noise characteristics of SiC JBS diodes were tested under stress conditions of 85% relative humidity,85℃ temperature,960 V reverse bias,and 168 hours.The degradation mechanism of the device under high temperature and high humidity reverse bias was analyzed.After reversed bias at high temperature and humidity,the leakage current decreased from 368.685 nA to 26.939 nA,which decreased by 340 nA,the withstand voltage increased by 60 V,and the noise amplitude decreased by 2E-12 V2/Hz.High humidity causes the metal electrodes of SiC JBS device to decompose,and the decomposed metal ions accumulate on the surface of SiC/Si O2 in the form of positive charges,which causes the effective negative charge at the interface to decrease,resulting in increased breakdown voltage and reduced leakage current.At the same time,high humidity reduces the density of interface defects,resulting in reduced noise.Through analysis and comparison,the leakage current and noise amplitude change greatly,reaching 90%,while the breakdown voltage change rate is only 3.98%.Therefore,the leakage current IR combined with the noise amplitude B parameter is more sensitive to characterize the damage of SiC JBS device under high temperature and high humidity reverse bias stress.Finally,this article applies a 140 A,10ms half-sine surge current wave to a SiC JBS device,and tests the device’s electrical characteristics and 1/f noise characteristics after repeated surge shocks of 0,500,1000,and 2000 times.Analyze the impact of repeated surges on device performance.After repeating the surge test,the forward voltage drop increased from 1.511 V to 1.541 V,the leakage current increased from 322 uA to 433 uA,an increase of 111 uA,the withstand voltage increased by 213 V,and the noise amplitude increased by 4E-13 V2/Hz.Under repeated surges,stacking fault growth occurs in the epitaxial layers of SiC JBS device,leading to an increase in forward voltage drop,an increase in leakage current,and a reduction in the withstand voltage of the device.At the same time,stacking faults will cause the number of minority carriers on the surface to fluctuate,resulting in increased 1/f noise.Through analysis and comparison,the change rate of noise parameters is the highest,which is 447.5%,and the change rates of forward voltage drop,reverse leakage current,and reverse breakdown voltage are all below 50%.Therefore,the noise amplitude B is selected to more accurately and sensitively characterize the anti-surge capability of the SiC JBS diode.Through high temperature reverse bias,high temperature,high humidity reverse bias,and repeated surge tests,this article finds that the reliability of the device is characterized by noise,which can more sensitively reflect the damage of the device under repeated surge stress.1/f noise can sensitively reflect many potential defects in semiconductor materials and devices,which are often difficult to characterize with existing testing and analysis methods.Therefore,the 1/f noise sensitive non-destructive characterization method is helpful to accurately and quickly analyze other types of stress damage,and has important guiding significance for the research on the reliability of JBS devices.