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

This work investigates the electrical properties of thin HfO₂ 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.