Thermally activated discharging mechanisms in SiNx films with embedded CNTs for RF MEMS capacitive switches

Abstract

In the present work, we investigate thermally activated processes in nanostructured SiNx films with embedded CNTs, which can be used in RF MEMS capacitive switches. Nanostructured films have been fabricated with a simple process, in order to incorporate CNTs on the lower SiNx layer and a reference SiNx material has been also fabricated with the same method (without CNTs), in order to compare the properties of the nanostructured films with the pristine material. Thermally stimulated depolarization currents (TSDC) assessment and a single-point Kelvin Probe (KP) system have been used in MIM capacitors, in order to investigate the electrical properties of the utilized films.The nanostructured material is found to exhibit lower charging and smaller discharging time, which makes it a promising candidate for RF MEMS capacitive switches. Thermally activated discharging mechanisms have been identified and the presence of CNTs is found to diminish a discharging mechanism with a characteristic time larger than five days at room temperature. Different discharging mechanisms are identified and distinguished for the first time, to the best of our knowledge, between a reference and a nanostructured SiNx dielectric film. Charge displacement in the bulk material during discharge takes place through hopping processes and larger mean hopping distance and zero field conductivity has been found in the nanostructured films. The reduction of the discharge characteristic time and the simultaneous suppression of trapping centers in the films with embedded CNTs indicate a direct relation between the macroscopic electrical properties and the microscopic defects in the dielectric material.