Design And Process Research Of Ultrahigh Voltage 4H-SiC MOSFET

Owing to the advantages of high voltage,high current,high frequency and low power consumption,SiC devices has greatly promoted the development of power equipment via its advantages of high efficiency,low energy consumption,and lightweight miniaturization,which has attracted much attention..Especially in the field of ultra-high voltage applications,SiC devices can replace traditional Si devices,and do not require complicated series-parallel structure,which reduces the number of system components,simplifies the circuit topology,and improves the power conversion efficiency.This paper aims to produce ultra-high voltage 4H-SiC MOSFET devices with a breakdown voltage above 10kV.Firstly,the thickness and doping concentration of the selected epitaxial layer were determined by theoretical calculation and simulation verification.Secondly,the main parameters of the were optimized by simulation.Finally,the deflected simulation of the above parameters verified that the selected parameter meet the requirements of ultra-high voltage.In order to achieve the goal of ultra-high voltage,a Multi-Zone Modulation Field Limiting Rings technology was proposed in this paper.The optimization parameters of this new structure were determined by simulation.And the blocking characteristics,implant dose window and sensitivity to the interface charge of the new structure and the traditional structure were compared through the above simulation.The key processes of manufactory of the ultra-high voltage 4H-SiC MOSFET were studied in this paper.And the difficulty of 4H-SiC MOSFET etching process and ohmic contact process were thoroughly analyzed and then improved.By the development of key process technologies,we have obtained an etching process that meets the process accuracy requirements and an N-type ohmic contact with a contact resistivity of10^-5?·cm².Using domestic SiC processing technology platform,the process and tests of ultra-high voltage 4H-SiC MOSFET device with blocking voltage above 10 kV are completed.The test results show that the 4H-SiC MOSFET with Multi-Zone Modulation Field Limiting Ring termination technology has a breakdown voltage of 13.6kV,which achieved a 95%termination efficiency,and the level of leakage current in the blocking state is only 10nA.Compared with traditional field limiting rings,the breakdown voltage is increased by 40%,which verified the improvement of the breakdown voltage efficiency of the new structure.This thesis carried out the simulation design,process development,device development and experimental tests of ultra-high voltage 4H-SiC MOSFET devices,which provides a reference for the research in this field.