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

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Solid-state materials for advanced technology, 2015-09, Vol.199, p.42-47
• Main Authors: Wzorek, M., Czerwinski, A., Borysiewicz, M.A., Gołaszewska, K., Myśliwiec, M., Ratajczak, J., Piotrowska, A., Kątcki, J.
• Format: Article
• Language: English
• Subjects: Annealing; Contact resistance; Diffusion barrier; Intermetallics; Microstructure; Morphology; Nickel; Nickel silicide; Nickel silicides; Ohmic contact; Silicides; Silicon carbide; Zirconium
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2015.04.012

•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.