The Study On 4H-SiC MOS Process And Electrical Properties

SiC, as a significant "third generation" material, gets highly attention in the "extreme electronics" study, because of the excellent performance under high temperature, high power and high radiation condition. It's also the only compound, which can grow natural oxide dielectric. Nowadays, the main course of SiC application is the research power devices, especially the MOSFET power devices. But the low channel mobility that caused by high interface states density is still the biggest problem. How to reduce the density is the first job to do in the study of SiC MOS devices. The main work of the paper is to reduce the interface states density by optimizing the MOS technology.The paper firstly investigates the MOS technology. Based on the standard Si process of the laboratory, the oxide is grown on the 4H-SiC substrate by dry oxidation. In order to improve the interface property, the post-oxidation anneal methods are used, including N₂ and wet re-oxidation anneal. Al is selected to evaporate on the substrate through the mask to form the electrode.The paper also works on the electronic characteristic of the MOS capacitor devices that fabricated above. By study on the I-V property, the reliability of the oxide is confirmed, whose breakdown field is as high as 10MV/cm. The Fowler-Nordheim tunnel current module is also employed to get the information of the energy band. In the C-V test, the charge in the oxide is figured out by studying on the flat band voltage of the MOS capacitor. On the other hand by using the Terman method and the HF-QS method, the distribution of SiO₂/SiC interface states density is investigated. The results show that the density is reduced to the number magnitude of 10¹¹eV^-1cm^-2 by optimized the processes of MOS capacitor fabrication.As a result of the study in the paper, it has been proved that the electronic characteristic of the MOS devices can be improved, and the interface states density can be reduced, all by using a wet ROA techonolgy. The result is significative to the further research.