Fabrication and characterization of nickel silicide ohmic contacts to n-type 4H Silicon Carbide

In this paper, we report on fabrication and characterization of nickel silicide ohmic contacts to n-type 4H-SiC. The contacts on Si-faced 4H-SiC were fabricated by DC magnetron sputtering of Ni and Si thin films. One set of structures has the Ni/Si/SiC scheme; the second one has the Si/Ni/SiC scheme. The Ni/Si thickness ratios of 66/60 and of 27/101 (nm) were designed to produce the stoichiometric Ni2Si and NiSi2 compound, respectively. The contact structures were annealed at 600 degrees C for 15 min, and subsequently from 800 to 1100 degrees C for 3-5 min in N-2 flow. The structure, composition, morphology and electrical properties of the contacts were examined using XRD, RBS, optical microscope and I-V measurements, respectively. The results indicate that the stoichiometric nickel silicides are formed after first step annealing (600 degrees C). Only the Ni2Si/n-SiC contact annealed at 1050 degrees C show Ohmic behaviour with low contact resistivity of rho(c) similar to 5x10(-4) Omega cm(2) and excellent surface morphology.