Raman study of Ni and Ni silicide contacts on 4H– and 6H–SiC

Ni2Si, NiSi and NiSi2 contacts were prepared on n-type 4H– and 6H–SiC(0001) by deposition of Ni and Si multilayers in the respective stoichiometry after high-temperature annealing, as well as pure Ni contacts. After annealing, the individual contacts were analyzed by Raman spectroscopy and electrical property measurements. Contact structures were then etched-off and subsequently observed by means of AFM (Atomic Force Microscopy). Ni reacted with SiC, forming Ni2Si and carbon. At NixSiy/SiC contact structures the respective silicides were already formed at low annealing temperatures, when only Schottky behavior of the structures was observed. The intended silicides, once formed, did not change any further with increasing annealing temperature. All contact structures provided good ohmic behavior after being annealed at 960 °C. By means of combined AFM and Raman analysis of the etched-off contacts we found that the silicide contact structures very probably did not react with SiC which is in accordance with the thermodynamic assumptions. After annealing the silicide contact structures at such temperature, when Schottky behavior changed to ohmic, a certain form of interaction between the SiC substrate and the silicide contact structures must have occurred.

► Ni and Ni silicides as electrical contacts on N-type SiC.
► Contacts examined by electrical measurements and Raman spectroscopy.
► Ohmic behavior of contacts was reached after annealing at high temperatures.
► Ni silicides showed to be non-reactive with SiC.