TDDB reliability assessment of gate oxides in commercial 1200 V SiC MOSFETs

The growing adoption of Silicon Carbide (SiC) MOSFETs in high-temperature and high-voltage applications has reinforced the need for robust gate oxide reliability evaluation. Time Dependent Dielectric Breakdown (TDDB) represents a principal wear-out mode that limits device lifetime. In this work, an adjustable TDDB testing framework is customised and presented for evaluating the gate oxide reliability of SiC MOSFETs under accelerated stress conditions. The system involves precise leakage current sensing, stressing voltage sensing, temperature monitoring, and automated data acquisition, enabling long duration stress tests with high resolution and repeatability. A complete TDDB campaign was executed on 25 commercially available 1200 V SiC MOSFETs at 175 °C, reaching 35 days of continuous operation. The results reveal clear degradation trends including progressive threshold voltage and on-resistance shifts, distinct gate leakage evolution, and failure time distribution consistent with wear-out behaviour. Finally, Weibull analysis was applied to extract lifetime parameters, demonstrating characteristic lifetimes depending on estimation method. This work provides experimentally validated reliability insights and establishes a benchmark dataset for future modelling and prognostic studies.