| Silicon carbide(SiC)is widely used in aerospace,power supply,high-speed railway and other fields with its wide band gap,low intrinsic carrier concentration,high thermal conductivity and high critical breakdown electric field.Silicon carbide is one of the most ideal materials for manufacturing power semiconductor devices applied in harsh environments such as high power,high temperature resistance,radiation resistance and surge resistance.Si C Schottky diode is the simplest and most popular power device.However,traditional junction barrier Schottky diode(JBS)is vulnerable to radiation,especially in aerospace applications which leads to premature device failure.In addition,the current distribution of the traditional merged Pi N Schottky diode(MPS)is uneven under the impact of surge current,which causes temperature to rise.In view of this,this thesis investigates the failure mechanism and reinforcement structure design of 4H-Si C Schottky diode single event effect and surge current reliability,improves the radiation and surge resistance of the device with minimal impact on its electrical performance.First of all,this thesis studies the failure mechanism of conventional JBS diodes under high-energy particles irradiation and the damage sensitive locations,and proposes new reinforcement principles and basis based on the shortcomings of existing literature on reinforced structures.Additionally,the surge current simulation of traditional MPS diode is also carried out to analyze the causes of uneven current distribution in the process of surge current,and the reinforcement idea is proposed.Second,a multi buffer layer JBS diode structure based on trench and double-layer P-type(MBDP-TJBS)is proposed in this thesis,and its single-event burnout performance is characterized and analyzed by Silvaco.The simulation results show that the electric field and temperature of the Schottky contact interface of MBDP-TJBS diode are significantly lower than those of the traditional multi buffer JBS diode because of its trench structure,and the maximum global temperature inside the MBDP-TJBS diode is also greatly reduced.When the reverse bias voltage is 1000 V and the linear energy transfer value is 0.5p C/μm,the maximum global temperature of the proposed structure is 1989 K,and the temperature of the Schottky contact interface is 439 K.These results demonstrate that the MBDP-TJBS diode has better single-event burnout performance.At last,a MPS diode with continuous P+ surface(CPS-MPS)structure is proposed in this thesis,and its surge current process is also characterized and analyzed by Silvaco.The simulation results present that the surface current distribution of CPS-MPS diode is uniform under the impact of surge current,which prevents the device from premature failure due to excessive temperature.Furthermore,CPS-MPS diode does not produce snapback effect when unipolar mode transitions to bipolar.Moreover,with CPS-MPS diode lower bipolar conduction voltage,it makes the device enter bipolar mode earlier in the process of surge current,reducing the device temperature,and improving the reliability of device surge current.Furthermore,the process steps of CPS-MPS diodes are the same as those of traditional MPS diodes with only different masks to be replaced. |
