Study Of Key Process For Silicon Carbide RSD Device

Silicon carbide is the third generation wide band gap semiconductor material with a wide band gap, high critical breakdown field, high electron saturated drift velocity and high thermal conductivity. Si C power semiconductor devices have a higher blocking voltage, lower on-resistance, lower power dissipation, greater cooling capacity than the conventional Si-based power semiconductors devices. In various structures of Si C materials, 4H-Si C is more widely used because of its high mobility of carriers and low anisotropy.Reversely Switched Dynistor(RSD) is a kind of power semiconductor switch which specifically applied to pulsed power field. Compared to other pulsed power semiconductor switching devices, RSD can turn on with high current density and high di/dt, and have a short turn-on time, RSD is easy to be series connection as well. Using Si C materials to make RSD can improve the blocking voltage and current density of the device, reduce conduction losses in high blocking voltage condition. And these advantages will make the Si C RSD device more valuable in high voltage and repetition frequency applications.There is still some process difficulties with Si C device fabrication at present, such as etch process, ion implantation, p-type omic. This paper have studied the fabrication process of 4H-Si C RSD devices,and research these process difficulties.As one of the most important process of 4H-Si C materials, the etching process have been mainly studied. Inductively coupled plasma(ICP) and CF4/O2 mixed gas was used to etch 4H-Si C material. The orthogonal approach was applied firstly to research systematically on the influence of the process parameters, including ICP power, RF power,CF4 and O2 flow, and the etch rate of 4H-Si C material. The results indicate that the etch rate increases as the ICP power or RF power increases, decreases firstly and then increases with the CF4 flow, and increases firstly and then decreases with the O2 flow. A maximum etch rate 213.47nm/min was acquired and the Root-Mean-Square surface roughness(RMS)was 0.724 nm, which showed its surface quality was good.The fabrication process of 4H-Si C RSD devices have been designed and researched.Before the experiment, the design of epitaxial wafer structure,the design of fabrication process and the lithographic was prepared. The wafer was customized and then processed through photolithography, magnetron sputtering, metal lift-off, ICP etching, ion implantation and annealing, and ohmic contact. Some of the key parameters were researched to obtain the best conditions for the production process,such as exposure time,development time, magnetron sputtering conditions, the ion implantation energy and dose,annealing conditions.The device was prepared preliminary and the forward blocking voltage was obtained about 600 V. These work is helpful to improve and optimize the Si C RSD device fabrication process.