Studies Of The Property Of Interface On SiO₂/6H-SiC And The Defects In SiO₂

The material of silicon carbide (SiC) has many good properties due to its wide bandgap. It can be applied to high-temperature, high-frequency and high-power devices. It is the only one compound semiconductor whose native oxide is SiO2. Therefore, the SiC devices can be manufactured using the technology of the silicon processing, for example MOS devices. But the quality of its oxide is far from adequate for industrial devices. The devices need high quality of oxide film and SiO2/SiC interface structure. In this paper, the high frequency C-V, the annihilation of slow positron beam and the infrared reflectance techniques were used to study the property of interface in SiO2/SiC, the defects in SiO2 and their physical characteristics.In the high frequency C-V experiments, the large flat-band shift in SiO2/ p-SiC indicated that there was high density of deep interface states. The deep interface states were simply studied by using photo excitation. In the experiment of photo-excited C-V characteristics of SiO2/ n-SiC, a ledge that had been appeared in p-type sample was observed because of the deep interface states. By comparing SiO2 p-SiC with SiO2/ n-SiC, it can be found that the deep interface states in SiO2/p-SiC is donor-type, while in SiO2/n-SiC is acceptor-type. Finally, different wavelengths of light-wave were applied to the photo-excited C-V, which indicated that the information of interface states could be obtained.The 0-15keV energy slow-positron beam was used to measure the Dopple broadening in SiO2/SiC. Both the S and W parameters clearly showed that the density of defect in SiO2 layer had decreased after annealing in N2. The results of this experiments indicated that the defects of void-type in the SiO2 layers decreased after annealing. It shows that the technique of annihilation of slow positron is a good method in monitoring the defect in SiO2.Infrared reflectance was used in measuring the characteristics of the SiO2 layer on SiC. A peak appeared at about 1100cm-1can be used to monitor the density of the SiO2 layer. After annealing in N2, the peak shifted towards high frequency. This shift became distinct after annealing at 1100 , which showed a decrease of the density and was considered that the interstitial impurity had diffused from SiO2.