Abstract
The growing demand for miniaturized and digitally integrated systems has accelerated the adoption of microelectromechanical systems (MEMS) across high-voltage applications, including electroseparation, microplasmas, and electrospraying. As these applications often operate in the kV range, dielectric reliability becomes a critical design consideration. This study presents a controlled, side-by-side comparison of breakdown behaviour, leakage current, and process compatibility of thermal SiO2, plasma-enhanced chemical vapour deposition SiO2, Low-pressure chemical vapour deposition SiNx, and atomic layer deposition (ALD)-Al2O3 using capacitive test structures with comparable film thicknesses. Thermal SiO2 exhibited the highest dielectric strength, reaching high fields of up to 24 MV/cm for a 54 nm dry oxide, although its ≥1000 °C processing temperature limits post-metallization compatibility. Among low-temperature options, ALD-Al2O3 demonstrated the most promising performance, with the best-performing process variation achieving a median breakdown field of 14.8 MV/cm and a median leakage current of 11 nA/cm² at 8 MV/cm for a 61 nm film deposited at 220 °C and annealed at 450 °C. These values exceed those reported for comparable thicknesses, highlighting the sensitivity of dielectric performance to both deposition and annealing conditions. The findings provide practical guidance for selecting dielectric materials that ensure substrate insulation reliability in high-voltage MEMS applications, balancing electrical performance with fabrication constraints.