Ti/TaSi2/Pt Metallization on n-Type 4H-SiC: Effects of the Thickness Ratio and Annealing on Ohmic Contact Stability at 600 °C

To improve the stability of ohmic contacts for SiC sensor chips operating at 600 °C, SiC/Ti/TaSi2/Pt ohmic contact stacks were fabricated on n-type 4H-SiC in this work. The effects of the Ti/TaSi2/Pt thickness ratio and annealing conditions on electrode performance were systematically investigated, and the resulting electrodes were characterized via SEM, XRD and AES. The results show that a lower specific contact resistivity (SCR) (7.16 × 10−5 Ω·cm2) is obtained after the Ti/TaSi2/Pt ratio of 1:3:2 (50/150/100 nm) is rapidly annealed at 1050 °C. The SCR remains 3.05 × 10−4 Ω·cm2 after 20 h of atmospheric aging at 600 °C, and the electrode surface remains flat enough for the subsequent processes. Taken together, the XRD and AES results suggest that the formation of well-crystallized TiC/TaC and Si-enriched titanium silicides lowers the specific contact resistance, and that the thermally stable phases, such as TaC, hinder oxygen ingress, which is consistent with the observed high-temperature stability. In contrast, oxygen penetrates into the contact interface and forms TiO2, an insulating oxide that increases the contact resistance and thereby degrades the contact performance. The results provide a basis for the design of ohmic contacts for high-temperature silicon carbide sensors.