The fabrication of nickel silicide ohmic contacts to n-type 6H-silicon carbide

This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi$_{2}$/SiC structure are formed on N-wells created by N$^{ + }$ ion implantation into Si-faced p-type 6H-SiC epilayer respectively. NiSi and NiSi$_{2}$ films are prepared by annealing the Ni and Si films separately deposited. A two-step annealing technology is performed for decreasing of oxidation problems occurred during high temperature processes. The specific contact resistance $\rho _{c}$ of NiSi contact to n-type 6H-SiC as low as 1.78$\times $10$^{ - 6}\Omega $cm$^{2}$ is achieved after a two-step annealing at 350~${^\circ}$C for 20 min and 950${^\circ}$C for 3 min in N$_{2}$. And 3.84$\times $10$^{ - 6}\Omega $cm$^{2}$ for NiSi$_{2}$ contact is achieved. The result for sheet resistance $R_{\rm sh}$ of the N$^{ + }$ implanted layers is about 1210$\Omega /\square$. X-ray diffraction analysis shows the formation of nickel silicide phases at the metal/n-SiC interface after thermal annealing. The surfaces of the nickel silicide after thermal annealing are analysed by scanning electron microscope.