Ni and Ni Silicides Ohmic Contacts on N-type 6H-SiC with Medium and Low Doping Level

Ni suicides contacts, which are expected to be advantageous contact materials on SiC, were tested in this work. Prepared contact structure were ohmic with low contact resistivity approximately 8 x 10(-4) Omega cm(2) after annealing at 960 degrees C as far as the SiC substrate with a medium doping level was concerned, no matter whether Ni or Ni silicides were used. At lower annealing temperatures, only Schottky behavior was observed by means of I-V characteristics measurements. In the case of SiC substrate with a low doping level, the behavior differed. It was necessary to anneal the structures at 1070 degrees C to see ohmic behavior appearing with resistivities reaching 8 x 10(-3) Omega cm(2) and this was valid only for Ni end Ni2Si. Raman spectroscopy measurements confirmed formation of single Ni silicides as expected. It was found that Ni silicides can keep as good resistivity as Ni contacts while they interact with SiC in limited way and their undesirable drop-like morphology is expected to be overcome for example with a covering layer.