Research On Energy Loss And Radiation Effect Of Silicon Carbide Trench Gate IGBT

With the increasing attention to energy conservation and environmental protection,power semiconductor devices play a more and more important role in human society.Besides,consumers' demand for power semiconductor devices is getting higher and higher.In addition,the rapid development of the communications industry in recent years has increased the demand for switching power supplies—higher switching frequency,smaller switching energy loss and smaller size.With the development of technology,how to reduce the energy loss of the trench gate IGBT without degrading its reliability,including the turn-off loss and the on-state power consumption characterized by the on-state voltage drop is always a hot research for researchers and also a bottleneck for IGBTs.However,for IGBT devices,there is a contradiction between the conduction power consumption and the turn-off loss.The industry generally uses the trade-off curve between the on-state voltage drop and the turn-off loss to measure the performance of the device.Therefore,this dissertation investigates the power consumption of a 15 kV 4H-SiC trench gate n-channel IGBT,mainly including Vce,on and Eoff.Some new structures have been proposed to solve above problem.In order to compensate for the shortcomings of the single event burnout research on 4H-SiC IGBTs,the triggering process of single event burnout effect in 4H-SiC trench IGBTs has been studied,and the anti-single event burnout ability of the new structures has been analyzed.The main work of this paper is summarized as follows:(1)For the typical 4H-SiC grooved gate IGBT devices,a grounded P+shielding region at the bottom of the grooved gate is usually introduced to reduce the electric field in the gate oxygen and improve the reliability of the gate oxygen.However,the introduction of P+shielding region also introduces two parasitic JFET resistors in the current path,which increases the on-state voltage drop of the device.In order to solve this problem,a new device structure called the emitter groove structure(E-P+-TIGBT)is designed on the basis on the analysis of the on-state power consumption.E-P+-TIGBT uses the emitter groove and its bottom's P+region to replace the P+shielding region at the bottom of the groove gate and adopts the depletion region generated by the P+region at the bottom of the emitter in the N-drift region to reduce the electric field of gate oxygen.The parasitic JFET resistor is removed to reduce the on-state voltage drop and reduce the conduction loss without degrading other electrical characteristics of the device.(2)In order to solve the problem that the extraction speed of excess carriers stored in the N-drift region is slow during the turn-off process,a collector Schottky contact structure S-TIGBT is designed based on the mechanism analysis of the turn-off loss.By introducing a reverse-biased Schottky junction on the collector side,a high electric field is introduced in the P-type collector region.Under the action of the electric field,the electrons reaching the P-type collector region are quickly extracted to the collector electrode,which speeds up the extraction of electrons.At the same time,the extraction speed of electron under the electric field is not affected by the temperature,achieving the purpose of reducing the turn-off loss and improving the temperature characteristics.(3)In order to solve the negative differential resistance effect in the I-V characteristic curve of the shorted anode structure(RC-IGBT),a new type of anode structure-integrated NPN collector structure(npn-TIGBT)has been proposed.By replacing the partial P+collector region with an N-type substrate,an NPN transistor in off-state is introduced on the collector side.The emitter junction of the NPN transistor,the P-type collector region/N-type substrate junction,is in a reverse-bias state regardless of whether the device is turned on or off.This introduces an additional electric field near the PN junction,forcing the electrons reaching the P-type collector to move into the collector electrode,thereby achieving the purpose of increasing the electron extraction speed and reducing the turn-off loss.(4)At present,the study on radiation effect of 4H-SiC based power semiconductor devices mainly focuses on MOSFETs and diodes,and there are few reports on the radiation effects of trench gate IGBT devices.In order to make up for the shortcomings of 4H-SiC trench gate IGBT radiation effect and provide a theoretical basis for its wide application in the field of strong radiation,the single-event burnout effect(SEB)triggering process of 4H-SiC trench gate IGBT is studied.Based on the single-event burning mechanism,the SEB characteristics of S-TIGBT and npn-TIGBT are studied.By reducing the current gain of the parasitic PNP transistor inside the device,the capability to resist the single event burnout is improved.