High-temperature electrical performance and interface adhesion performance of SiC-based Pt thin-film RTDs

Developing high-performance SiC-based platinum thin-film resistance temperature detectors (RTDs) capable of stable operation over 800 °C in air, with superior electrical performance and interfacial mechanical stability, is crucial for improving the high-temperature measurement accuracy of silicon carbide pressure sensors. Therefore, this study investigated the influence of adhesion layer materials and annealing conditions on their high-temperature electrical performances, including the temperature coefficient of resistance (TCR), consistency across multiple tests, electrical stability, and adhesion strength to the SiC substrate. More importantly, two different types of protective layers were introduced to suppress Pt film agglomeration at high temperatures and improve the high-temperature stability of the RTDs. The results showed that Pt thin-film resistors with tantalum (Ta) and aluminum oxide (Al₂O₃) adhesion layers maintained functionality in air up to ~855 °C, demonstrating good linearity and high TCR. At 800 °C, the resistance drift rates of Pt thin-film RTDs with Ta and Al₂O₃ adhesion layers were 0.538%/h and 4.159%/h, respectively. With the addition of a yttria-stabilized zirconia (YSZ) protective layer, these rates decreased to 0.291%/h and 0.146%/h, significantly enhancing stability. The critical load (Lc₂) of the Pt thin-film on the SiC substrate with a Ta adhesion layer was 45.65 mN, which decreased to 11.96 mN after annealing. In contrast, for the Pt thin film with an Al₂O₃ adhesion layer, the critical load (Lc₂) increased from 13.13 mN to 16.46 mN after annealing. The investigation of electrical performance and interface adhesion performance at high temperature in this work provided a reliable combination of adhesion layers for developing SiC-based temperature and pressure integrated sensors applied in extreme environments.