Dielectric breakdown and reliability of thin film insulators for high-voltage microelectromechanical systems applications

• Direct benchmarking of SiO 2 , SiN x , and Al 2 O 3 dielectrics under identical processing • High breakdown fields of 20-24 MV/cm achieved in >50 nm thermal SiO 2 films • ALD-Al 2 O 3 shows very low leakage and breakdown fields exceeding reported values • Process-performance trade-off analysis guides dielectric choice for high-voltage MEMS 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 SiO 2 , plasma-enhanced chemical vapour deposition SiO 2 , Low-pressure chemical vapour deposition SiN x , and atomic layer deposition (ALD)-Al 2 O 3 using capacitive test structures with comparable film thicknesses. Thermal SiO 2 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-Al 2 O 3 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.