How to select the right current collector and dielectric films for the next-generation high-voltage 3D electrolytic micro-capacitors?

The growing demand for miniaturized autonomous microdevices within the Internet of Things (IoT) ecosystem necessitates compact, high-voltage, on-chip energy storage solutions. This work presents a systematic characterization of the electrochemical properties of atomic layer deposition (ALD)-grown Al 2 O 3 and Ta 2 O 5 dielectric films deposited on various current collector for electrolytic micro-capacitor operating in aqueous electrolyte. Four planar electrode configurations, namely Pt / Al 2 O 3 , Al / Al 2 O 3 , Pt / Ta 2 O 5 and TaN / Ta 2 O 5 , were compared to select the most suitable current collector. The Pt-based electrode exhibited a stability window of ca. 1 V versus Ag/AgCl, constrained by oxygen evolution at 1.2 V vs Ag/AgCl. This work shows as well that Al / Al 2 O 3 and TaN / Ta 2 O 5 electrodes have a greater stability (0–10 V versus Ag/AgCl), attributed to self-healing anodic oxidation, due to a good cation-matched interfacial chemistry, and reduced leakage currents. High temperature X-ray diffraction and X-ray reflectivity revealed that annealing temperatures of sputtered TaN / ALD grown Ta 2 O 5 films should be restricted to 500°C under N 2 / H 2 to both ensure film densification and to prevent oxidation and increased resistance in TaN.