Radiation Effects Of Proton On Wet Oxidation 4H-SiC MOS Capacitor And SBD

The excellent physical and electronic properties?i.e.wide band gap,high breakdown field,and high thermal conductivity?make silicon carbide?SiC?a potential semiconductor material for fabrication power electronic devices,enabling operation at higher voltage,higher temperature,higher frequency and strong radiation environment.Now,SiC power devices,such as SiC SBD diodes and SiC MOSFETs with certain advantages,are beginning to apply in space electronic devices.So studying the radiation effects of SiC MOS structure and SBD systematically is important for improving the radiation resistance of SiC-based electronic devices and the lifetime of the device.Moreover,the MOS capacitor and the SBD diode have a common oxide layer and epitaxial layer structure,which can provide a certain basis for the interpretation of the radiation effects.The SRIM simulation of proton incident MOS capacitors shows that 5MeV protons will cause ionization and displacement effects in both SiO₂ and SiC.And the energy loss is concentrated in the range terminals,while energy deposition is basically uniform in the oxide layer,SiO₂/SiC interface and epitaxy,which we are more concerned with.Both in SiO₂ and SiC,the electronic stopping power is much greater than the nuclear stopping power.For SiO₂,the energy loss is mainly used for ionization,but for SiC,electron-hole pairs generated by ionization effect can be recombination very fast,displacement effect is mainly considered.The radiation resistance of 4H-SiC MOS capacitors that were annealed in NO for different times after wet oxygen was compared.Due to the ionization effect in the oxide layer,a large number of electron-hole pairs were generated,and the acceptor defect was introduced by displacement effect into the epitaxial layer.therefore,there are several changes after irradiation:the positive flatband voltage shift,a decrease in capacitance,an increase in C-V hysteresis and a decrease in the SiO₂/4H-SiC interface state depending on the irradiation fluence.With respect to the interface states,we have analyzed from several aspects,mainly including the break of C=C double bonds and further passivation,and the passivation of Si and C by N and H atoms.Finally,it is considered that the MOS capacitor has better radiation resistance when the annealing time in NO is two hours.The proton irradiation effects of 4H-SiC SBDs with two different structures were compared,which provided some evidence for the mechanism analysis of MOS.The capacitance of the field plate structure is lower than that of the conventional structure SBD.The carrier concentration of the epitaxial layer extracted from the C-V characteristic decreases gradually,which causes the increase of the series resistance.Also,Proton irradiation results in an increase of the ideal factor?n?and a decrease of the Schottky barrier height??_B?of the SBD,which leads to an increase of the hot electron emission current?J₀?and the tunneling current?J_T?in the reverse current.Meanwhile,the defect introduced by the displacement effect acts as a recombination center and also causes an increases of recombination current?J_W?.The DLTS test results show that proton irradiation introduces three new electron traps in the SiC epitaxial layer,and eliminates or converts an existing energy level to other defect types.Finally,only the charge in the oxide layer can be released by room-temperature annealing,but the displacement damage can't be eliminated.In the high temperature annealing,when the temperature is added to 75°C and125°C,a small part of the displacement damage is recovered.At 175°C,the displacement damage is obviously recovered,but some are still not eliminated.For the first time,the proton irradiation effect of wet oxidation 4H-SiC MOS capacitors and SBDs has been studied.It is of great significance to study the radiation resistance of SiC devices.