Ti and Ti/Sb ohmic contacts on n-type 6H-SiC

Ohmic contacts consisting of Ti and Ti/Sb were prepared on silicon and carbon face of 6H-SiC with different doping densities. Ni contacts were used as reference. All structures were gradually annealed at different temperatures. Specific contact resistance was measured and morphology was monitored after each annealing. it was found that the same metallization has different properties on different 6H-SiC polar faces. Sb addition to Ti contact helped to reach lower values of specific contact resistance on Si-faces of substrates. On C-faces of substrates, pure titanium contacts were comparable or better than Ti/Sb. Annealing at 960 degrees C and 1065 degrees C caused contact morphology deterioration and surface spreading of Ti and Ti/Sb contacts. Ni contacts kept good morphology at all annealing temperatures and had the best values of specific contact resistance after annealing at 960 degrees C and 1065 degrees C. Using XPS profiling only small amount of free carbon was found in Ti-based contacts. (c) 2008 Elsevier B.V. All rights reserved.