Study On Properties Of Nitrided SiC MOS Interface By Gray-Brown Method

Silicon Carbide is being intensely pursued around the world for high temperature, high power, high frequency and high radiation applications because of its wide bandgap, high electric field strength, high saturation electron velocity and high thermal conductivity. It’s the only compound semiconductor material which can generate the intrinsic oxide-SiO2through thermal oxidation. This makes it easy to fabricate SiC MOS devices according to mature silicon processes. However, the great potential of SiC MOSFETs has thus far been hampered by unacceptabe low inversion channel mobility. One of the main reasons is the high interface states density between oxide and SiC. To reduce the interface state density of SiO2/SiC interface is the crucial technical problem in the research of SiC MOS device.In this paper, SiC MOS capacitors were fabricated and ECR nitrogen plasma was used to treat the SiO2/SiC interface. Gate oxide quality was characterized by using current-voltage test. The breakdown field of the oxide was9.92MV/cm. J-E data was analyzed by the Fowler-Nordheim tunnel current model and the barrier height between SiO2and SiC was2.69eV which was closed to the theoretical value of2.72eV. SiO2/SiC interface properties were evaluated by capacitance-voltage characterization. Gray-Brown technique was used to extract the Dit lying energetically within0.2eV of Ec. The temperature dependence of low temperature capacitance-voltage data was analyzed using Gray-Brown method and the room temperature capacitance-voltage data was analyzed by Hi-Lo method to obtain interface trap density lying energetically within～0.05-0.6eV of the conduction band edge (Ec). The interface states density was reduced to2.91×1013cm-2eV-1at～0.05eV below Ec and at～0.2eV below Ec the interface states density of1.33×1012cm-2eV-1was achieved.The results revealed that nitrogen plasma process is an effective method for passivating interface traps and improving the MOS interface properties. The interface state density lying～0.05-0.6eV below Ec was reduced and meanwhile the oxide showed good quality.