Si ohmic contacts on N-type SiC studied by XPS

Abstract

Si ohmic contacts on N-type 4H- and 6H-SiC with contact resistivity comparable with Ni metallizations were prepared. After etching-off of the Si contacts and deposition of new, unannealed ones, good electrical parameters of the original contacts remain preserved. Such unannealed secondary contacts were already successfully created with original Ni or Ni silicide metallizations. An advantage offered by the secondary contacts prepared after the original Si contacts is that they are prepared on a high-quality SiC surface as the original Si does not react with SiC. XPS and AFM analyses were carried out. Under the original Si contacts when they are etched-off there is observed a shift of Si and C peaks to higher binding energies in comparison with a clean, bare SiC surface. After less than 2nm of the surface layer is sputtered-off the shift disappears. We suggest that preserved electrical parameters after the etching-off of the Si contacts stem from a SiC surface modification.