Electrical Properties Of Nitrogen Plasma Modified SiC MOS Interface

Silicon carbide (SiC) is a very promising material in the fields of high temperature, radiation resistant, high frequency and high power devices due to its excellent properties, such as wide band-gap, high critical breakdown electric field, high thermal conductivity, high saturated carrier drift velocity. Besides, SiC is the unique compound semiconductor material which can be thermal oxidized to form SiO₂ insulating film in a similar way to silicon. This property offers the possibility of manufacturing SiC metal-oxide-semiconductor field-effect transistors (MOSFET) drawing lessons from the processes of silicon. However, the channel mobility of practical SiC MOSFET is very low due to the high SiO₂/SiC interface trap density. As a result, how to reduce the SiO₂/SiC interface trap density has become a very important problem.In this paper, the origin of the SiO₂/SiC interface trap density and the research methods were introduced at first. Then the SiC device process was investigated. The oxide was grown on the 4H-SiC substrate by dry oxidation. In order to improve the interface property, the nitrogen plasma was used to treat the SiO₂/SiC interface, the N plasma was obtained by Electron Cyclotron Resonance (ECR) plasma system, which could produce a small damage in the oxide film. The N plasma treatment effect was investigated through comparing the different samples.The paper mainly studied the electronic properties of the MOS capacitors, which were obtained through different processes. The reliability of the oxide film was evaluated by the Fowler-Nordheim tunnel current modle and the I-V characteristic test. The obtained breakdown field of the oxide film was as high as 9.96 MV/cm, and the barrier height of the SiO₂/SiC system was 2.70eV. In addition, the result indicated the N plasma treatment didn't deteriorate the voltage withstand property of the oxide film. The HF-QS C-V characteristic test was conducted, the SiO₂/SiC interface trap density distribution and the charge distribution were obtained. The result also showed that the SiO₂/SiC interface trapdensity was as low as 2.27×10¹²cm^-2eV at Fermi level.In summary, the results of this paper showed that the N plasma process could improve the SiO₂/SiC interface properties. The low SiO₂/SiC interface trap density was obtained, while the voltage withstand property of the oxide film was very good. These results play an important role in studying and improving the SiC MOSFET process.