Research Of Hot-carrier Reliability For Segmented Shallow Trench Isolation LDMOS

The power LDMOS(Lateral Double-Diffusion Metal Oxide Semicionductor,LDMOS)transisitor is widely used in smart power integrated circuits due to its high breakdown voltage,low on-resistance,and compatibility with CMOS processes.The segmented shallow trench isolation LDMOS devices have shorter current paths than traditional shallow trench isolation LDMOS devices,effectively reducing on-resistance.However,as a power output device,the device operates in a high voltage and high current density environment for a long time,and faces severe hot carrier reliability problems,which affects the working life.Therefore,it is of great significance to comprehensively study the hot carrier reliability of the device.The accelerated stress method is used to evaluate the hot carrier degradation of investigated LDMOS,and combined with 3D-TCAD(Three Dimensions-Technology Computer Aided Design)simulation technology and charge pump mechanism characterization technology,the inner degradation mechanism has been studied in depth.The research shows that under the maximum substrate current stress,the interface state generated at the shallow trench corner near the source is the main mechanism leading to the on-resistance degradation with a monotonously increasing trend.For the maximum gate voltage stress,the main damage point is transferred to the segmented shallow trench corner near the drain,and interacts with the interface state at the other corner to cause degradation of the device's on-resistance.On this basis,the effects of structural parameters on the device hot carrier reliability are studied respectively.It shows that the narrower segmented shallow trench,the longer field plate shrinkage length and the wider field plate shrinkage width will cause terriable hot carrier reliability.In addition,the effects of different layout structures on the hot carrier reliability of the device are also studied.Because of the increased vertivcal electric field and impact ionization rate,the hot carrier degradation of the device is more evident in the open ended and stepped layouts.Finally,based on the above research on the hot carrier degradation mechanism of the segmented shallow trench isolation LDMOS device,a new "H" shaped segmented shallow trench isolation structure is proposed.The size of the third shallow trench and the shrinkage field plate are reasonably optimized,and the measurement results show that the hot carrier reliability is significantly improved.