Amorphous Ni–Zr layer applied for microstructure improvement of Ni-based ohmic contacts to SiC

• Thin Ni–Si layers on SiC were studied after annealing.
• Different types of microstructural defects occur depending on Ni:Si ratio.
• Mechanisms leading to morphology degradation are discussed.
• Presented method improves the microstructure of ohmic contacts to SiC.

The new approach to fabrication process of nickel-based ohmic contacts to silicon carbide (SiC) is presented. During the first annealing step (300 °C), the amorphous Ni–Zr layer retards diffusion between two nickel silicide layers, thus handling the contradictory requirements for optimal Ni:Si ratio. Different stoichiometry obtained in each silicide layer allows to preserve smooth interface with SiC and simultaneously to avoid relatively easily meltable Si-rich Ni–Si phases during high temperature annealing (1000 °C) and therefore prevents morphology degradation. After annealing at 1000 °C only one final nickel silicide layer is present and Zr atoms are agglomerated at its surface. Morphology of the final silicide layer is substantially improved when compared to typical Ni-based contacts obtained by similar high-temperature annealings. The improved microstructure of the ohmic contact is a promising advantage in terms of SiC devices reliability.