A Study On The Tddb Characteristics Of Gate Oxide Layer In 4H-SiC MOS Devices

Silicon carbide(SiC)is a third-generation semiconductor material with excellent properties.It has many excellent physical and electrical properties such as wide band gap,high breakdown electric field,high saturation drift rate,and high thermal conductivity.It is the ideal material for the power devices operated in high temperature and high frequency.The SiC power devices can get the gate oxide by oxidation.The fabrication process is similar to the Si devices which is helpful with the manufacture of the SiC power devices.Due to the interface trap,the gate oxidation will be broken with lower activation energy and the breakdown voltage is reduced.Thus,the research of the reliability with the VLSI are focused on the time-dependence dielectric breakdown and the time-zero dependence dielectric breakdown.In this paper,the time-dependence dielectric breakdown of the SiC MOSFET and the interface characteristics is discussed with mechanism an experiment.The material characteristics of SiC and the fabrication process of the SiC power MOSFET are fully investigated.What's more,the oxidation is analyzed with the Deal-Grove model.And the breakdown caused by the interface trap charge are introduced.The reliability of the gate oxidation are studied with the E model.In order to develop a stable and repeatable high-temperature gate oxide oxidation process,a high-temperature oxidation experiment of a 4H-SiC MOS capacitor at 1200 ? to 1550 ? was performed in this paper.The breakdown voltage,barrier height,and breakdown charge of the gate oxide layer were measured.The influence of different high-temperature oxidation processes on the reliability of the gate oxide layer is further enhanced by statistical distribution.The breakdown voltage and the charge at 1250 ? match the best result,which are 11.21 MV/cm and 5.5×10-4,respectively,and the barrier height(2.43 eV)is the closest to the theoretical value.When the temperature is higher than 1 250 ?,the generated reliability decreases.Then,the influence of the high-temperature dry oxygen oxidation process on the interface is also studied,and the related parameters such as flat band voltage and interface state density are tested and analyzed.The effect of high temperature oxidation process on the device lifetime is discussed with the TDDB.This is due to the fact that when the oxidation temperature is too low,C residues will occur,and if the temperature is too high,vacancy oxygen will be introduced.