Characterization and Reliability Study of an Al-Doped HfO₂-Based High-Density 2.5-D MIMCAP

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 HfO <tex-math notation="LaTeX">₂</tex-math> high- <tex-math notation="LaTeX">κ</tex-math> 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/mm <tex-math notation="LaTeX">²</tex-math> while retaining a leakage current lower than 0.3 pA/nF at 2 V and 100 <tex-math notation="LaTeX">∘</tex-math> C. It offers a quadratic voltage coefficient of capacitance around 500 ppm/V <tex-math notation="LaTeX">²</tex-math> at 25 <tex-math notation="LaTeX">∘</tex-math> C and a temperature coefficient of capacitance of 191 ppm/ <tex-math notation="LaTeX">∘</tex-math> C. The breakdown field of this high- <tex-math notation="LaTeX">κ</tex-math> dielectric is around 6.2 MV/cm at 25 <tex-math notation="LaTeX">∘</tex-math> 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-mm <tex-math notation="LaTeX">²</tex-math> capacitors are expected to survive ten years with a failure rate lower than 1 ppm when operated at 100 <tex-math notation="LaTeX">∘</tex-math> C using voltages below or equal to 2.22 V.