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In this article, the reliability assessment of a 2.5-D metal–insulator–metal (MIM) capacitor, built in a thicker back-end of line layer using a 23-nm-thick ALD-deposited Al-doped HfO2 high- $\kappa $ dielectric, is performed using time-dependent dielectric breakdown (TDDB) measurements. This capacitor, compatible with back-side power delivery network (PDN) technologies, presents a density above 16.7 nF/mm2 while retaining a leakage current lower than 0.3 pA/nF at 2 V and 100 °C. It offers a quadratic voltage coefficient of capacitance around 500 ppm/ $\text{V}^{{2}}$ at 25 °C and a temperature coefficient of capacitance of 191 ppm/°C. The breakdown field of this high- $\kappa $ dielectric is around 6.2 MV/cm at 25 °C. The thermochemical formalism commonly used to describe dielectric breakdown was unsuccessfully tested on this device, confirming the joint contribution of current and field in the degradation process. In addition, the time to failure (TTF) temperature dependence is found to follow an Arrhenius mechanism. Assuming a power law (PL) extrapolation model, 800-mm2 capacitors are expected to survive ten years with a failure rate lower than 1 ppm when operated at 100 °C using voltages below or equal to 2.22 V.