Improvement of high temperature stability of nickel contacts on n-type 6H-SiC

The structural and electrical characterisation of nickel contacts on n-type silicon carbide was performed to improve the ohmic behaviour at high temperatures. The formation of nickel silicide (Ni2Si) was observed after annealing in vacuum of Nil SiC samples at 600 degreesC, as well as after rapid thermal annealing (RTA) in N-2 at 700 for 60 s. The carbon was almost uniformly distributed inside the Ni2Si layer, as monitored by energy dispersion X-ray analysis (EDX). The specific contact resistance rho (c) was determined by the transmission line method (TLM) for different values of the substrate carrier concentration N-D. Ohmic contacts with rho (c) = 3.9 x 10(-5) Omega cm(2) were obtained for substrates with N-D = 7.4 x 10(18) cm(-3) after RTA in N-2 at 950 degreesC. The optimised contacts maintain their electrical stability even after annealing in NZ up to 1000 C.