Design And Reliability Study Of High Voltage 4H-SiC MOSFET

Si IGBT is one of the main switching devices used in power electronic circuits.However,the bipolar characteristics of IGBTs not only limit the switching speed of the device but also increase the turn-off loss.Compared with Si IGBTs,SiC MOSFETs have higher switching speeds,lower switching losses,and superior operating capability at high temperatures,making them a powerful alternative to silicon IGBTs.This article aims to produce a high reliability 1200V 4H-SiC MOSFET devices.Firstly,the parameters of epitaxial layer are determined by theoretical calculation and verified by simulation.Then,the Pbase injection scheme,the thickness of the oxide layer,the length of the channel,and the width of the JFET region are optimized by simulation.Afterwards,Considering the large electric field of the gate oxide layer when the MOSFET device breaks down,a strengthening structure with JFET trenching and injection is proposed.Based on previous planar MOSFETs,the JFET implant window size,trench depth,and JFET width were optimized.Finally,the simulation results of the two devices are compared.According to the simulation results and the existing process conditions,the layout of the designed gate oxide reinforced MOSFET is drawn,and a the work of tape-out is performed.The static and dynamic test results of the packaged sample show that the blocking voltage of the device is 1620V,the on-state resistance is 2.3?and the threshold voltage is 2.9V.The input capacitance,output capacitance and reverse transfer capacitanc are 390pF,25pF and 5pF,respectively,when V_DS=800V.The device was tested in a power circuit where the inductive load.the results show that turn-on and turn-off losses were 0.170 mJ and 0.033 m J,respectively.the reliability test conditions are determine,through the investigation of Si power MOSFET reliability standards and foreign company-related reliability test conditions.Good performance devices were selected for reliability assessment.The assessment items included high temperature grid bias?HTGB?,high temperature reverse bias?HTRB?,temperature cycling?TC?,and steady state damp-heat reverse bias?H3TRB?.The assessment results show that the device has higher reliability under above four stresses.The 40 devices participating in the assessment?10 for each assessment?passed the assessment.Based on the domestic platform,the thesis carried out the development and reliability evaluation of high reliability 4H-SiC MOSFET devices,which promoted the industrialization of SiC MOSFET devices in China.