Nanotribology-based novel characterization techniques for the dielectric charging failure mechanism in electrostatically actuated NEMS/MEMS devices using force–distance curve measurements

The work presents a comprehensive package of novel nanoscale characterization techniques to study dielectric charging in electrostatic nano- and microelectromechanical systems (NEMS and MEMS). The proposed assessment methodologies are based on the force–distance curve (FDC) measurements performed using an atomic force microscope (AFM) to measure, for the first time, the induced surface potential and adhesive force over charged dielectric films. They were employed to study plasma enhanced chemical vapor deposition (PECVD) silicon nitride films for application in electrostatic capacitive RF MEMS switches. Three different techniques were introduced including the application of FDC measurements to study charging in bare SiNx films, metal–insulator–metal (MIM) capacitors, and MEMS switches. The results from the three methods were correlated and compared with the published data from other characterization techniques, mainly charge/discharge current transient (C/DCT) and Kelvin probe force microscopy (KPFM). The unique advantages of the proposed FDC-based characterization techniques are twofold. First, they can measure the multiphysics coupling between the dielectric charging phenomenon and tribological issues at the interface between the switch bridge and the dielectric surface. Second, the FDC-based techniques can measure larger levels of induced surface potential over charged dielectric films which results from the high electric field normally used to actuate MEMS switches. Based on the proposed FDC techniques, the influence of several parameters on dielectric charging/discharging processes was investigated: the dielectric film thickness, deposition conditions, substrate, and electrical stress conditions.

(a) An example of the adhesive force maps measured over a charged SiNx film using force–distance curve (FDC), (b) the induced adhesive force and surface potential increases with the charging electric field; the induced adhesive force decays with time due to (c) charge build in the dielectric film, and (d) charge relaxation.Figure optionsDownload high-quality image (129 K)Download as PowerPoint slideHighlights
► Novel characterization techniques to study dielectric charging in MEMS.
► Techniques use force–distance curve (FDC) measurements performed by an AFM.
► Measured the surface potential and adhesive force induced over charged dielectrics.
► FDC measures meniscus force and larger levels of surface potential on the nanoscale.
► We correlate between results from proposed techniques and other methods (C/DCT, KPFM).