Surface roughness, asperity contact and gold RF MEMS switch behavior

Abstract

Modeling predictions and experimental measurements were obtained to characterize the electro-mechanical response of radio frequency (RF) microelectromechanical (MEM) switches due to variations in surface roughness and finite asperity deformations. Three-dimensional surface roughness profiles were generated, based on a Weierstrass-Mandelbrot fractal representation, to match the measured roughness characteristics of contact bumps of manufactured RF MEMS switches. Contact asperity deformations due to applied contact pressures were then obtained by a creep constitutive formulation. The contact pressure is derived from the interrelated effects of roughness characteristics, material hardening and softening, temperature increases due to Joule heating and contact forces. This modeling framework was used to understand how contact resistance evolves due to changes in the real contact area, the number of asperities in contact, and the temperature and resistivity profiles at the contact points. The numerical predictions were qualitatively consistent with the experimental measurements and observations of how contact resistance evolves as a function of deformation time history. This study provides a framework that is based on integrated modeling and experimental measurements, which can be used in the design of reliable RF MEMS devices with extended life cycles.

Dynamics of the contact between a ruthenium surface with a single nanoasperity and a flat ruthenium surface: Molecular dynamics simulations

“…Although a variety of approaches have been used to study ideally flat surfaces 6-10 the contact surfaces of MEMS are rough 11 with a high density of nanoscale asperities. Probabilistic, 12,13 and fractal [14][15][16][17] approaches have been used to describe the correct topography of metal surfaces.…”

Molecular scale analysis of dry sliding copper asperities

“…As mentioned earlier, these asperity sizes are chosen to obtain a reasonable balance between nano-scale representation and the computational time and power required. The typical surface roughness of MEMS/NEMS surfaces (Bora et al 2005;Rezvanian et al 2007; Ansari and Ashurst 2011) was used as a reference for choosing these sizes.…”

Finite Element Based Surface Roughness Study for Ohmic Contact of Microswitches

“…Many researchers have devoted to analyzing and modeling the contact behavior and calculating the resistance. Several main methods are following, statistical [1][2][3][4], fractal [5][6][7], multi-scale [8][9] and determinist model [10]. The elastic or elastic-plastic deformation is considered in the above models, and the contact condition and material properties are studied, too [11].…”