Reliability Characterization And Mechanism Research Of High DV/dt Of SiC Power Diode

The third-generation semiconductor material,silicon carbide(Si C),as a material for preparing Pi N diodes,is more competitive than traditional Si-based Pi N diodes in terms of high power,high temperature,radiation resistance,and switching speed.However,because of its high-speed and high-power advantages,it is facing a d V/dt reliability problem that is more severe than that of Si devices.This article focuses on the reliability problems faced by Si C power diodes under the rapidly rising reverse voltage pulses.The main contents of the work are as follows:Firstly,this paper conducts high d V/dt pulse experiments on the 2400V 4H-Si C Pi N diode developed by our research group.The reverse characteristic of the device was significantly degraded after a single pulse stress of 1714 V/ns.Through the comparison of experiment and simulation,it is found that the d V/dt stress has two different degrees of influence on the diode:(1)High d V/dt stress will cause a local peak electric field at the junction of the terminal and the active area,leading to the occurrence of avalanche in advance.When the d V/dt value is high enough,a concentrated high electric field will be generated at the junction of the active area and the terminal area of the device.This will cause irreversible damage to the reverse blocking characteristics of the device,severely degrade the breakdown voltage,and greatly increase the leakage current.The incomplete ionization of the p-type impurity aluminum(Al)in the Si C material causes the depletion region to expand more slowly under high d V/dt stress and cannot keep up with the voltage rise.Therefore,the inner side of the terminal region has to bear more high peak electric field.Larger impurity ionization energy and faster voltage pulse signal will cause more serious electric field concentration.(2)The high d V/dt stress will bring in electorn accumulation at the interface between Si O₂ and the terminal area,so that the electric field in the terminal area is concentrated to the outside of the terminal,and the reverse leakage current increases,the breakdown voltage only slightly drifts,and the degradation is recoverable.Both the simulation and C-V test results show that d V/dt stress will make lots of electorn trapped at the interface between Si O₂ and the terminal area,change the electric field distribution in the terminal area,and cause the leakage current of the device to increase.Device performance will gradually recover with the release of trapped electrons.Secondly,the robustness of d V/dt of 4H-Si C Pi N diodes with different terminals is discussed.Keep the rising rate of the pulse signal 2000 V/ns,and take the ionization rate integral to 1during the d V/dt process as the criterion for the dynamic breakdown of the device.Compare the dynamic-static breakdown voltage states ratio of the 4H-Si C Pi N diodes with different structures of JTE terminal and FLRs terminal to analyze its robustness of d V/dt.For JTE terminals:the electric field of Two-Zone JTE terminal structure is more uniform than that of the Single-Zone JTE structure.The peak electric field of TZ JTE structure in the d V/dt process is lower than that of the SZ JTE,and the robustness of d V/dt is significantly better than the SZ JTE structure.For the FLRs termials,the influence of two parameters,the ring spacing S and the distance S₁ from the first ring to the active area are mainly discussed.The electric field distribution of the non-uniform FLRs terminal is more uniform than that of the uniform FLRs,and the robustness of d V/dt is stronger than that of the uniform FLRs.The parameter S₁ of the non-uniform FLRs terminal has a greater impact on the ability to resist d V/dt stress.The dynamic-static breakdown voltage ratio of the non-uniform FLRs with S₁of 1?m and the ring spacing increment?S of 0.2?m reaches 99.1%.