Study Of Ohmic Contact To N-type 4H-SiC

Silicon Carbide is the most promising materials for high-power, high-temperature, high-frequency, and radiation hard device applications. Ohmic contact is one of the fundamental requriements for SiC devices with high performance, and it is a difficult problem in the manufacturing process. In this thesis, our studies concerned three aspects such as SiC surface treatment, the choice of electrode material and preparing processes, testing and analysis technology of circular transmission line model(CTLM).In this paper, we choose n type 4H-SiC materails as the research object, select NiCr alloy, Ti, TiC as electrode materials. The current-voltage curve and the specific contact resistvityρ_c of metal-semicondutor contacts are measured using transmission line model(TLM) and two kinds of circular transmission line model(CTLM); X-ray diffraction(XRD) measurement was used to identify the intermetallic compound formed at the metal/n-SiC interfaces in the various annealing temperarue, in order to judge chemical stability in the metal/SiC interface and analysis a correlation between the electrical properties and the microstructure; the factors affecting ohmic contact and the theory mechanism are comprehensively analysis, through surface treatment, electrical analysis and improved materials process combined, we expect to explore a reasonable way to lower specific contact resistvity of ohmic contact.For the Ohmic contacts, Ni-based metals was used as contacts to n type 4H-SiC, in this thesis, NiCr was choosed to metal material, the metal/SiC contact was ohmic contact after annealing at high temperatures. At 400℃the lowest specific contact resistanceρ_c was 5.69×10^-5Ω·cm².In this paper, the low temperature preparing processes and electrical characters of Ti ohmic contacts on n type 4H-SiC substrates were studied. By hydrogen plasma surface cleaning 4H-SiC surface, the as-deposited Ti contacts were ohmic contact., the specific contact resistanceρ_c was 2.25×10^-3Ω·cm² at room temperarure, by the means of circular transmission line model(CTLM). With increasing the annealing temperarue, ohmic behavior of the contacts improved gradually, after annealing at 400℃the lowest specific contact resistanceρ_c was 2.07×10^-4Ω·cm².