Simulation Study Of Breakdown Characteristics Of 4H-SiC Buried-Channel MOSFET

SiC-based devices will play more and more important role in the applications of the electronic system operated in some extreme environments, such as at high temperature and high radiation. The high breakdown electric field and high saturated electron drift velocity make SiC-based devices cater for high power and high frequency applications. To decrease the influence of interface state, Buried Channel MOSFET formed by implanted n-type layer near SiO2/SiC interface is developed. Simulation study on the electrical breakdown characteristics is needed to realize the potential of the promising high voltage device-4H-SiC BC MOSFET. The main tasks in this thesis are as follows:It has been done to develop the basic model and improved parameters of 4H-SiC BC-MOSFET for accurate simulation, such as mobility model and imcomplete ionization model. Operational modes of the buried-channel MOSFET are verified with these models. The I-V characteristics have been simulated at room temperature and high temperature, which prove the advantage of this novel device. All these establish a foundation for following study of breakdown characteristic of the device.To better analyze breakdown characteristics of 4H-SiC BC MOSFET, the depth of the device and the width of drain region should be increased in terms of the requirement of MEDICI. In this case, the mechanism of breakdown of 4H-SiC BC MOSFET is more understood. Simulated results show the breakdown voltage of 4H-SiC BC MOSFET is larger than surface channel MOSFET, which indicates the potential of BC MOSFET to act as power device. Also it is shown that the breakdown voltage of 4H-SiC BC MOSFET increases with gate bias, channel density, channel depth and oxide thickness, decreases with substrate doping concentration. And the breakdown voltage becomes larger with increasing temperature.Latest fabrication of 4H-SiC BC MOSFET is brought forward.It is indicated that the threshold voltages of each device are positive,so these devices are normally-off.The tested I-V characteristics show good linear and saturation characteristics.The maximum effective mobility is about 90cm2/Vs.The obtained effective mobility indicates the superiority of SiC BC MOSFET,which shows the feasibility of improving mobility with SiC BC MOSFET structure.But great difference between experimental and reported mobility still exists,further modificative scheme is suggested.