The influence of surface topography on the electromechanical characteristics of parallel-plate MEMS capacitors

Abstract

Variable parallel-plate microelectromechanical system (MEMS) capacitors have been used extensively in various applications. The performances of MEMS capacitors are traditionally predicted by considering the electrodes to be atomically smooth and, therefore, roughness effects are ignored. However, recent studies have shown the significant influence of surface topography on the performance and reliability of microelectronic capacitors and other solid-state devices. Hence, the objective of the present study is to yield insight into the impact of surface topography on the elecromechanical characteristics of MEMS capacitors. Specifically, closed-form analytical solutions are derived for the capacitance, electrostatic force, pull-in gap and voltage, electric field, and adhesion force by utilizing simple roughness representation. The significant effects of surface topography on the performance and reliability of MEMS capacitors are elucidated and discussed in the context of the presented results. Surface topography dominates the electromechanical characteristics of MEMS capacitors via the combinatorial influences of larger surface area and smaller effective gap between the electrodes. It is shown that adhesion forces, typically, have negligible influence on the pull-in phenomenon. More accurate description of the roughness by utilizing the statistical approach is also considered and a numerical example is presented for MEMS capacitors with polycrystalline silicon electrodes.

Modeling and modification of the parallel plate variable MEMS capacitors considering deformation issue

“…The structure of the capacitor plays a very important role in predicting the accurate capacitance, reducing the voltage requirement (which is an important characteristic in today's RF circuit) and enhancing the quality factor. Kogut presented insight into the impact of surface topography on the electromechanical characteristics of MEMS capacitors [10]. Krylov illustrated the influence of the higher order correction on the pull-in behavior for a large deflection model of a one-dimensional string [11].…”

Implicit spectrally-accurate method for moving boundary problems using immersed boundary conditions concept

“…1) and star denotes complex conjugate. Such problems are of interest in the case of nano-channels and nano-switches where the effects of surface roughness could be significant [7]. The slot is periodic with wavelength k = 2p/a and extends to ±1 in the x-direction.…”

Effect of electrode surface topology on charge injection characteristics in dielectric liquids: An experimental study

“…Numerical studies have been performed to determine the effect of electrode spacing, shape, size and tip radius on electric field enhancement [13,14]. Kogut [13], in case of air, found for a rough surface with hemispherical structures on one electrode and the other being atomically smooth that the field enhancement factor, defined as the ratio of the electric field at the hemispherical tip to that of a smooth electrode, increased significantly when the radius of curvature of the hemisphere was reduced.…”

“…Kogut [13], in case of air, found for a rough surface with hemispherical structures on one electrode and the other being atomically smooth that the field enhancement factor, defined as the ratio of the electric field at the hemispherical tip to that of a smooth electrode, increased significantly when the radius of curvature of the hemisphere was reduced. This effect was much more significant compared to the effect of the inter-electrode distance.…”