This work presents a novel failure analysis technique for the dielectric charging phenomenon in electrostatically driven MEMS devices. The new reliability assessment methodology makes use of Kelvin Probe Force Microscopy (KPFM) and it targets in this specific work thin PECVD silicon nitride films for electrostatic capacitive RF MEMS switches. The proposed technique took advantage of the AFM tip to simulate charge injection through asperities then measure the induced surface potential. The impacts of bias amplitude, bias polarity, and bias duration employed during charge injection have been explored. Various parameters have also been investigated: dielectric film thickness, substrate nature, and SiN material deposition conditions. FTIR and XPS material characterization techniques have been used to determine the chemical bonds and compositions, respectively, of the SiN films being investigated. The required samples for this technique consist only of thin dielectric films deposited over planar substrates and no photolithography steps are required. Therefore, the proposed methodology provides a low cost and quite fast solution compared to the currently available methods.

A method that allows the investigation of discharge transport mechanism in dielectric films used in MEMS capacitive switches or MIM capacitors or even bare dielectric films is presented. The method is based on monitoring the dielectric film surface or MIM top electrode potential decay rate and the dependence of conductivity on surface potential. The method has been applied in MEMS and MIMs with simultaneously deposited dielectric film to confirm the closeness of transport data in MIM and MEMS devices. The impact of non-uniform charging on local discharge rate and different dielectric film stoichiometry has been also assessed. Finally, the effect of surface leakage due to environment humidity has been also investigated. [2019-0159]

Physics of Charging in Dielectrics and Reliability of Capacitive RF-MEMS Switches | InTechOpen, Published on: 2010-03-01. Authors: George Papaioannou and Robert Plana

The discharging processes in silicon nitride dielectric film of RF-MEMS capacitive switches are investigated for the first time. The study includes the dependence of discharging as a function of temperature that allows the detection of thermally activated mechanisms. The discharging time constants were found to depend only on temperature and not on the actuation bias polarity.

This paper investigates the effect of spontaneous polarization of magnetron-sputtered aluminum nitride on the electrical properties and reliability of Radio Frequency – Micro-Electro-Mechanical Systems capacitive switches. The assessment is performed with the aid of application of thermally stimulated polarization currents in metal-insulator-metal capacitors and temperature dependence of device capacitance. The study reveals the presence of a surface charge, which is smaller than that expected from material spontaneous polarization, but definitely is responsible for the low degradation rate under certain bias polarization life tests.