Ni hetero-alloying electrodes for 4H-SiC pressure sensor over wide temperature range: interfacial dynamics and leadless integration

Interfacial thermal degradation of ohmic contacts and the instability of packaging structures constitute the primary bottlenecks compromising the reliability of 4H–SiC piezoresistive pressure sensors in harsh environments. In this study, molecular dynamics simulations were employed to elucidate the atomic-level kinetic mechanisms underlying the ohmic transition at the Ni/SiC heterointerface. Guided by comparative experimental analysis, a Ni/TiW/TaN–Au/TiW/Au composite electrode system was developed. This system achieved a low contact resistivity of 8.31×10^-5Ω cm² while exhibiting excellent electrical stability at 600°C. Surface analysis and depth profiling revealed that bulk atomic interdiffusion, driven by oxygen intrusion along grain boundaries, serves as the dominant mechanism governing electrode failure at elevated temperatures. Furthermore, elemental and simultaneous thermal analyses were utilized to characterize the composition and thermal rheological properties of the glass paste, facilitating the design of a stepped integrated sintering process. This approach enabled the leadless hermetic interconnection of the pressure sensor chip, eliminating fracture risks associated with traditional wire bonding. A variable-temperature pressure calibration platform was established to conduct static calibration tests from -50°C to 450°C. A surface reconstruction algorithm was introduced to decouple pressure-temperature cross-sensitivity and compensate for repeatable nonlinearity and thermal drift under calibrated conditions. The sensor's performance metrics under extreme conditions were significantly enhanced. The sensor successfully withstood a continuous 20h survival test, validating its engineering potential for pressure sensing in extreme environments.