Study On The Effect Of Gate Degradation On IGBT Devices

As a representative of new power electronic devices,insulated gate bipolar transistor(IGBT)has the advantages of high input impedance of MOSFET,fast switching speed,strong current carrying capacity of GTR,and high withstand voltage,so it has become the core component of high-power power electronic devices such as flexible converter valve,and is widely used in various flexible engineering.As the weak point of IGBT devices,gate oxide will inevitably lead to various reliability problems with the increase of operation time.In this paper,the high-voltage and high-power welded IGBT is taken as the research object,and the aging characteristics and mechanism of IGBT devices are studied by combining theoretical analysis with experimental verification.Firstly,by analyzing the switching transient process of IGBT under inductive load,the physical expressions of various electrical parameters including threshold voltage,Miller platform voltage,turn-off delay time,turn-on delay time,turn-off loss and turn-on loss are obtained,and on this basis,the aging characteristics of various electrical parameters of IGBT are theoretically analyzed,which lays a solid theoretical foundation for the subsequent experimental study of gate oxide aging.Secondly,the experimental scheme of accelerating gate oxide aging is designed.Based on BTR-9 experimental equipment,high-temperature gate bias experiments are carried out for 168h,500h and 1000h,and the influence laws of gate oxide aging on threshold voltage,Miller platform voltage,turn-off delay time and switching loss are obtained.It is determined that most of the dynamic and static parameters of devices will show an upward trend after high-temperature gate bias experiments,in which the threshold voltage growth rate of some devices is nearly 4%after 1000h aging experiments.Based on the performance of devices at home and abroad before and after the aging test,it is concluded that the reliability of a domestic manufacturer’s high-voltage and high-power welded IGBT is still far from the same type of products abroad.Finally,in order to explore the influence mechanism of electric stress,thermal stress and electrothermal coupling stress on the aging of IGBT gate oxide,three groups of control experiments are designed.The experimental results show that the aging process of IGBT gate oxide will be greatly accelerated after the electrothermal coupling stress acts on IGBT devices at the same time,which is 3.5 times that of gate-emitter voltage alone and nearly 30 times that of temperature alone.Based on the above conclusions,a mechanism about the formation and evolution of internal defects in the gate oxide layer of high voltage and high power IGBT is revealed,and the research results provide support for further understanding the failure mechanism of IGBT gate.