Preparation of 4H-SiC/Ti/TaSi₂/Pt high-temperature lead electrodes based on secondary sputtering

Under high temperature and pressure conditions, silicon-based devices experience leakage and deformation due to the self-heating effect, rendering them incapable of long-term stable operation. Silicon carbide (SiC), as a representative third-generation semiconductor material, is an ideal choice for high-temperature, high-frequency, and high-power electronic devices. However, the high-temperature performance limitations of 4H-SiC devices stem from the stability of ohmic contact electrodes and metal interconnects. Current lead electrodes suffer from output instability issues, and oxygen ingress at high temperatures can easily cause output failure. Previous studies indicate that the SiC/Ti/TaSi₂/Pt multilayer structure exhibits excellent potential for ohmic contacts. Building upon this ohmic contact foundation, this study proposes a batch sputtering-annealing process to fabricate high-temperature-resistant lead electrodes. This involves altering the sequence of annealing and sputtering: first sputtering Ti/TaSi₂ onto the SiC substrate and annealing to form the ohmic contact, followed by depositing a Pt protective layer to construct a novel SiC/Ti/TaSi₂/Pt electrode structure. Comparative analysis of the two experimental groups was conducted using SEM, AES, XRD, thin-film stress measurement, and semiconductor analyzers. The batch-sputtered and annealed electrode structure exhibited enhanced density and reduced residual stress, with an initial specific contact resistivity of 6.35 × 10⁻⁵ Ω·cm². High-temperature aging tests at 600°C demonstrated superior electrical stability for electrodes formed by sputtering Pt onto Ti/TaSi₂ after ohmic contact formation. These electrodes maintained ohmic characteristics even after 20 hours of air aging, whereas conventional cosputtered ohmic contacts transitioned to Schottky contacts. Pt effectively suppressed atomic diffusion and oxidation reactions, resulting in a smooth electrode microstructure without curling. The batch sputtering-annealing process not only significantly enhances the overall performance of SiC ohmic contacts but also provides crucial guidance for the structural design and performance improvement of ohmic contacts using other metal combinations. This approach holds significant reference value for the high-temperature packaging of third-generation semiconductor power devices and the development of electronic systems operating in harsh environments.