Simulation Study Of 4H-SiC Trench MOS Barrier Schottky Power Diode

As a wide band-gap material,Silicon carbide(SiC)is endowed with high thermal conductivity,strong critical electric field and fast electron saturation drift.Compared to the traditional silicon based device,SiC power device has very low power loss,making it quite attractive for high-temperature,high-frequency and high-power applications.The trench MOS barrier Schottky(TMBS)has been successfully used in silicon field for its lower on-resistance and good schottky electric field shielding compared to JBS diode.However,a strong reverse bias electric field is distributed in the oxide layer which exceeds the withstand field of the oxide layer,yielding the TMBS structure unsuitable for the SiC field.By adding the P+shielding region on the trench bottom,the high electric field in the oxide layer in the 4H-SiC TMBS is reduced,making the breakdown voltage rise.However,the P+region form PN junction with the N-drift region,which increases the ON-resistance of the device.This paper proposed an improved structure of the 4H-SiC TMBS with a lower ON-resistance and higher devices FoM(BV2/Ron-sp).1.N wrapping region 4H-SiC TMBS:by adding doping concentration of N-drift region around the P+region properly,the on-resistance of the device could be reduced for narrower PN depletion layer and wider current path.The electric characteristics of the proposed structure have been studied and the doping concentration and width of the N-type region has been optimized using SILVACO numerical simulation software.Finally,the specific ON-resistance is decreased by 32.2%,and the FoM is increased by 48.4%,respectively,compared with the conventional TMBS.The breakdown voltage basically unchanged up to 1908V.2.Side wall enhanced 4H-SiC TMBS:by adding the doping concentration of N-drift region at the trench bottom and along the trench wall using ion implantation,the hindrance of P+region to the forward current of the device has been reduced as the width of the PN junction depletion layer reduced and the channel resistivity declined.To comprehend the theory of the improved structure deeply,the forward conductive analysis model has been constructed.After the doping concentration and width of the side wall enhanced layer was optimized using simulation tool,the specific ON-resistance and the FoM was improved by 38.4%and 61.3%,respectively,the breakdown voltage was basically unchanged.What's more,the electric field in oxide layer was under 2.5MV/cm,and that in the schottky interface was under 0.6MV/cm.