Analysis And Optimization Of Hot-carrier Degradation For U-shaped Channel SOI-LIGBT

Lateral insulated gate bipolar transistor based on silicon on insulator substrate?SOI-LIGBT?has been widely used in the field of power Integrated Circuits?ICs?for its good isolation,high breakdown voltage and easy integration.The U-shaped channel SOI-LIGBT uses a bent channel to increase the area of the N⁺emitter,which greatly improves the current capability of the device and reduces the area of the smart power ICs.Nevertheless,the U-shaped channel SOI-LIGBT usually works under the conditions of high temperature,high voltage and high current,it suffers from serious hot-carrier reliability issue,and the lifetime of device will be affected eventually.Therefore,a detailed research on the hot-carrier degradation mechanism of U-shaped channel SOI-LIGBT is urgently needed.In this thesis,the hot-carrier degradation mechanism of U-shaped channel SOI-LIGBT is investigated by the method of 3D-TCAD?Three Dimensions-Technology Computer Aided Design?simulation,the electrical parameter degradation test and charge pumping test.The results reveal that the main degradation mechanism is the generation of interface states and the hot electron injection at the channel region under high V_GE and low V_CE dynamic stress.For Unclamped Inductive Switching?UIS?stress,the dominating degradation mechanism is hot holes trapping into the bird's beak and the device surface closing to the end of poly gate.In addition,the influences of structure parameters on the hot-carrier reliability has been investigated.The results show that the vertical type U-shaped channel and the emitter P⁺/N⁺interval structure have more obvious hot-carrier degradation.The AC-HCI?Alternating Current-Hot Carrier Injection?parallel test platform built in this thesis not only greatly improves the efficiency of hot-carrier reliability assessment under dynamic stress,but also ensures the accuracy of hot-carrier reliability assessment.Based on the investigation of degradation mechanism,three kinds of novel device structure including extra P-type region in the drift,step-doping drift region and collector P⁺/N⁺interval structure are proposed to optimize the hot-carrier degradation.The optimized device with extra P-type region in the drift reduces the peak value of the impact ionization rate and the perpendicular electric field by 75%and 26%without sacrificing the current capability of the device.