Failure Mechanism of Ti/TiN/Pt Ohmic Contacts to n-type 4H-SiC after High Temperature Annealing Treatment in Air

In this paper, the failure mechanism of Ti/TiN/Pt ohmic contacts to n-type 4H-SiC applied to capacitive pressure sensors at high temperature in air is studied from three aspects: electrical performance, surface microstructure, and chemical composition analysis. In terms of the electrical performance, as the treatment temperature and the time increased, the specific contact resistances of the ohmic contacts increased from a minimum of 0.91 to a maximum of 141 mΩ•cm
²
, and the ohmic behavior degraded to rectifying behavior at 700°C. The increased roughness and material shedding on the electrode surface affect the conductivity of the contact. In the air treatment environment, not only inter-diffusion and chemical reactions occurred within the multilayer system, but also oxygen atoms were introduced, generating metal oxide and silicon oxide, which greatly reduce the electrical performance of the electrode. In addition, the consumption of the TiN intermediate barrier layer further enhance the diffusion of materials and oxygen atoms in the multilayer structure, destroying the stability of the electrode structure and causing the failure of the ohmic contacts.