Low-power Structure Design Of 4H-SiC Trench Gate IGBT

SiC,known as the third-generation semiconductor material,has received widespread attention from researchers in recent years.This is because SiC has a wider band gap width,higher critica l breakdown electric field,and higher electron saturation drift rate compared to Si.At the same time,SiC is more competitive than Si in high-irradiation and high-temperature environments.As an important component of power semiconductor devices,SiC IGBTs have high forward conduction current density and low forward conduction voltage drop due to conductance modulation effects.On the other hand,IGBT has both the advantages of withstanding high voltage and high temperature because of the application of SiC.The SiC IGBT with the above characteristics will become the main force of power semiconductor devices in the high-voltage,high-current high-power field,and gradually replace traditional power semiconductor devices in high-speed rail transmission networks,high-voltage power grids,and new clean energy.This article improves the traditional SiC IGBT structure,and uses Silvaco TCAD software to design and simulate two sets of improved structures to improve the performance of SiC IGBT.Based on the research and improvement of the traditional trench gate 4H-SiC IGBT structure,the core work can be summarized as the following two parts:A 4H-SiC PTC-TIGBT structure with a partially trenched collector was designed to reduce the turn-off energy loss in the first part.This structure introduces a trench collector deep into the N-drift region on the collector side,and adds a P+ collector that is not covered by the N-buffer layer above it.The trench collector provides more hole injection,which enhances the conductance modulation effect in the N-drift region,thereby reducing the forward voltage drop when the 4H-SiC PTC-TIGBT is conducting in the forward direction.During the 4H-SiC PTC-TIGBT turn-off process,the trench collector provides a low-resistance path for electrons and an extra electric field to accelerate electron extraction.The two work together to shorten the turn-off time of the device and reduce the turn-off energy loss.In order to maintain a forward breakdown voltage of 15 k V,the 4H-SiC PTC-TIGBT increases the size of the N-drift region,which increases the size of the device.Improving forward breakdown voltage degradation is an important issue to be addressed.In the second part,this article designs an optimized 4H-SiC NPN-IGBT structure to improve the problem of lower forward breakdown voltage of 4H-SiC PTC-TIGBT.This structure improves forward withstand voltage and turn-off energy loss while slightly losing forward characteristics,and its N-drift region size is consistent with the control structure.Its structure is characterized by inserting part of the N,P,N layers with high doping concentration in the N-buffer layer to compromise forward voltage drop and turn-off energy loss.Using the reverse bias NPN structure when the 4H-SiC NPNTIGBT is in the blocking state to optimize the electric field distribution in the N-drift region,accelerate the extraction of excess carriers in the N-drift region,and optimize the forward withstand voltage and turn-off energy loss.