Research On High Speed IGBT Structure With Electric Field Enhancement Unit

Power semiconductor devices are widely used in various fields because of their superior power conversion capability.IGBT is the representative product of the third technological revolution of power semiconductor devices.It combines the advantages of high input impedance,simple driving,strong current capability of BJT and low on-off voltage of MOSFET.As a dual-carrier conductive device,IGBT has a high electron concentration and hole concentration in the drift region during the conduction period,which makes the device have a good current capability.At the same time,due to the conductive modulation effect in the drift region,IGBT devices also have a low conduction voltage drop.However,the removal of excess carriers in the drift region is slow when switching off,which results in the tail current phenomenon of IGBT devices,slows down the switching speed of devices and limits the application scope of IGBT.In order to suppress the trailing current phenomenon and improve the switching speed of IGBT devices,a new high-speed IGBT structure with electric field enhancement is proposed based on the understanding of the working principle of IGBT and the mechanism of trailing current generation.The structure is applied to the Lateral IGBT and the Vertical IGBT devices respectively.The new structure proposed in this paper introduces an electric field enhancement unit based on the traditional IGBT structure.When the device is turned off,the electric field enhancement unit produces an electric field pointing from the collector region to the drift region,which promotes the hole injection into the drift region and the recombination with the excess electrons in the drift region,speeds up the removal of excess carriers in the drift region and improves the switching-off speed of the device.At the same time,when conducting,the electric field also exists,which can improve the conduction current density and reduce the conduction voltage drop of the device.The introduction of PN junctions and high K dielectrics in the electric field enhancement unit can effectively balance the electric field in the drift zone when the device is turned off and improve the breakdown voltage of the device.In order to verify the performance improvement of the new structure proposed in this paper,we use Medici simulation software to simulate the switching performance,conduction performance and voltage withstanding performance of the new structure and the traditional IGBT structure.According to the simulation results,compared with the traditional IGBT structure,the proposed high-speed IGBT structure can effectively improve the switching speed of the device and basically eliminate the trailing current phenomenon of the IGBT device.Compared with the traditional IGBT device,the oncurrent density can be increased by an order of magnitude at most,and the breakdown voltage can also be improved to a certain extent.The process simulation of the Lateral IGBT structure with electric field strengthening unit are also carried out by using Tsuprem4 simulation software,and imports the process simulation results into Medici to re-simulate the related performance.The simulation results show that the process simulation results are basically in line with the device design expectations.The switching characteristics,conduction characteristics and voltage withstanding characteristics of the device are consistent with the results of direct use of Medici simulation.