Investigation On Design And Fabrication Of High Performance 4H-SiC IGBT

Silicon carbide(SiC),as a representative third generation wide band gap semiconductor material,has been widely used in high power,high temperature,radiation resistance and other military and civilian application domains,due to its superior physical and chemical properties.Silicon carbide insulated gate bipolar transistor(IGBT),as a voltage driven wholly-controlled power device,is the forefront and hot spot in the field of power electronic devices.Research and development of SiC IGBT with high performance and reliability is of great significance to the high efficiency and miniaturization of power electronic equipment and the reduction of production and maintenance cost.At present,there are still some problems in the research of SiC IGBT:(1)high voltage SiC IGBT with voltage above 10 k V has requirements on the area intensification,process tolerance and interface charge sensitivity of the terminal structure.The conventional terminal structure is difficult to meet all these aspects at the same time.(2)The bipolar carrier storage effect of SiC IGBT will lead to large device switching loss.Some methods such as local carrier lifetime modulation and buffer injection modulation are not optimized enough or affect the current sharing performance in parallel.These problems can be solved by the reported extraction enhancement devices,but the process is complex.It is necessary to propose a device structure with sufficient modulation level and simple fabrication method to improve the switching loss of SiC IGBT at high frequency.The main work and achievements are as follows:(1)Design and research of 10 k V 4H-SiC n type high voltage terminal with electric field modulation inside the field stop ring.In this paper,the effects of the parameters of the terminal field stop ring on the breakdown efficiency and interface charge sensitivity of high voltage power devices are studied.An end enhanced multi-floating-zone junction terminal extension structure(EE-MFZ-JTE)with electric field modulation structure on the tail side of the main terminal region and the inner side of the field stop ring is proposed.Considering the simplified fabrication process and the tolerance of process parameters,the multi-floating-zone electric field modulation ring structure is selected to study the influence of relevant parameters on the charge sensitivity of the terminal interface.The results show that EE-MFZ-JTE can significantly reduce the interface charge sensitivity compared with conventional multi-floating-zone junction terminal extension(MFZ-JTE).At the same time,compared with the conventional field limiting ring terminal(FLR),EE-MFZ-JTE has significant advantages in the sensitivity of interface charge and area intensification.The simulation results show that the new structure can improve the positive interface charge tolerance of the terminal by 66.7%compared to the conventional MFZ-JTE,also the termination area reduced by 21%compared to the FLRs at the same interface charge sensitivity level,which can meet the tolerance requirements of general process conditions,and ensure the device reliability requirements under irradiation and other conditions to a certain extent.(2)Design and research of a novel switch-frequency improved vertical 10 k V 4H-SiC IGBT with multi-zone collector.Based on minority carrier injection and extraction modulation mechanism,a novel switch-frequency improved vertical 4H-SiC IGBT is designed and studied.The minority carrier concentration in the drift layer is effectively controlled by carrier injection and extraction modulation,and a good compromise between conductive voltage drop and switching loss is achieved.The new structure has a positive temperature coefficient of the on-state voltage,which ensures that the device has good current sharing characteristics.Compared with the conventional counterpart,the switching loss of the proposed device is reduced by 81.5%and the average power consumption is reduced by 63.1%when the duty cycle is 50%.It is shown that this structure can work at higher frequency,which will help to improve the energy conversion efficiency and total harmonic distortion of power electronic system.(3)Device design and key process research of 10 k V 4H-SiC p-IGBTAccording to the basic principle and simulation results of the device,the key parameters of the device are optimized,the layout and process flow are designed.The 10 k V 4H-SiC p-IGBTs have been prepared.When the gate bias is-40 V and the conduction current density is 100 A/cm~2,the conductive voltage drop is 8.3 V,and the differential specific on-resistance is 38.9 m?·cm~2.When the device power density is limited to 300 W/cm~2,the current density can reach 47.6 A/cm~2,the corresponding conductive voltage drop is 6.4V,and the differential specific on resistance is 31.1 m?·cm~2.When the gate voltage is 0 V,the forward blocking voltage of FLR terminal device is larger than 10 k V,the leakage current is 50.2 n A,and the corresponding current density is 7.47?A/cm~2.The forward blocking voltage of MFZ-JTE terminal device is 9800 V.The conduction characteristics of the device are superior to the similar devices reported domestically.The main problems are that the threshold voltage is too high and the breakdown voltage of MFZ-JTE is lower than the design value.The results of device characterization and analysis show that high N-well surface concentration and low terminal ion implantation dose are the main reasons for high threshold voltage and low breakdown voltage of MFZ-JTE.In conclusion,based on studying the basic principle of 10 k V SiC IGBT and the relationship between device parameters and characteristics,this work focuses on the research of 10 k V SiC IGBT with high breakdown voltage,high area intensification and low interface charge sensitivity.The n-type high-voltage terminal structure design improves the process tolerance and reliability of the device.A novel switch-frequency improved vertical 10 k V SiC IGBT with multi-zone collector is studied,which shows great improvement of the compromise energy consumption compared to the conventional counterpart.The key parameters,layout and process flow of the device were designed,and the 10 k V 4H-SiC p-IGBT device was prepared.The device reached the domestic advanced level.The influence of device key structure and parameters on characteristics is verified by testing and analysis,which has important reference value for the in-depth research of the device.