Design Of Split Gate Power MOSFET Device With Wide SOA

Split gate power MOSFET devices are widely used in communication,industrial automation,transportation and consumer electronics for the advantages of high switching speed,low loss.The system can be maintained without interruption by hot swap technology,so as to improve the reliability of the system.Split gate power MOSFET devices with wider safe operating area(SOA)are required in hot swap technology.However,in order to obtain lower characteristic on resistance,the chip area is becoming smaller and smaller,resulting in the SOA greatly reduced,which can not meet the requirements of hot swap technology.The purpose of this research is to optimize the SOA of traditional split gate MOSFET and design a split gate power MOSFET with wide SOA.Firstly,the working principle of split gate power MOSFET is introduced,and the electrical characteristics and safe working area of the device are described in detail.Then the failure mechanism of the device operating beyond the safe working area is analyzed.It is found that the secondary breakdown is the main cause of the device failure,and it is mainly related to the temperature coefficient.Then,the effects of pbody doping concentration on the temperature coefficient are analyzed.Based on the study,a device structure with wide SOA are proposed,which is split gate with open channel.The open channel structure achieves wide SOA by reducing the channel width,however,increasing the on resistance of the device.Therefore,based on the open channel,a new type of composite gate structure is proposed,which can realize a wider SOA without increasing the on resistance by introducing planar gate.So the composite gate power MOSFET is the optimal structure.The simulation results show that the breakdown voltage of the composite gate power MOSFET device is 108 V,the threshold voltage is 4.2V,the on-resistance is 4.85m?,the SOA boundary is38A/cm~2.So all performance parameters are up to design index requirements.