Ohmic Contact Characteristics of Silicon Carbide-based MEMS Devices

The stability and reliability of electrical ohmic contacts are the key to the stable operation of silicon carbide power electronic devices in extreme environments. Firstly, the current research status and common problems of SiC ohmic contacts has been analyzed. Secondly, a carrier model for the ohmic contact between metals and SiC based on the tunneling effect is established. By increasing the doping concentration of the substrate SiC, the Schottky barrier width can be reduced, which is more conducive to the formation of ohmic contacts. Thirdly, 200nm thick Ni metal layer was deposited on 4H-SiC substrate with a doping concentration of NA=2e19cm-3. Finally, the effect of high-temperature thermal annealing temperature on metal ohmic contact is studied and results show that Ni can form ohmic contact with SiC when the annealing temperature exceeds 800°C. Scanning electron microscope and atomic force microscope are used to observe the contact surface. After high-temperature thermal annealing, the electrical properties are guaranteed, but metals indicate defects such as cluster precipitation. Therefore, it is possible to prevent the contact layer metal from being damaged by adding other covering metals.