On the electrical properties of ALD HfO2 dielectric films for MEMS capacitive switches

This work investigates the electrical properties of thin HfO 2 dielectric films grown by Atomic Layer Deposition (ALD) for application in RF-MEMS capacitive switches. The motivation arises from the need to optimize dielectric performance in these devices, particularly concerning dielectric charging, breakdown behavior, and conduction mechanisms. A key challenge addressed is the influence of deposition temperature on the structural and electrical behavior of the films, which transitions from amorphous to polycrystalline with temperature. The study utilizes a wide range of techniques including current-voltage measurements, impedance spectroscopy , Kelvin Probe potential decay, and Thermally Stimulated Depolarization Currents (TSDC) on Metal–Insulator-Metal (MIM) devices. The key findings indicate that grain boundary formation in polycrystalline films significantly alters the breakdown voltage , charge transport, and trapping mechanisms. It is worth noting that, films deposited at 100–150 °C exhibit hopping conduction and lower leakage, while those at 200–250 °C demonstrate ohmic or Space Charge Limited Current (SCLC) behavior due to crystallization. These results provide insight for selecting suitable deposition parameters to engineer dielectric materials for reliable MEMS switch operation. • Electrical properties of RF-MEMS capacitive switches with ALD HfO₂ dielectric films • Atomic Layer Deposition (ALD) HfO2 with substrate temperatures of 100°C, 150°C, 200°C, and 250°C. • Current-voltage, impedance, surface potential decay, and TSDC measurements. • Breakdown voltage in HfO₂ films. • Amorphous and micro-nano crystalline HfO2 films.