Modeling of a resisitive contact RF-MEMS switch fabricated using DRIE

Abstract

In recent years there has been a dramatic increase in the number of wireless applications in both commercial and markets such as defense. Radio Frequency RF) Micro Electro Mechanical Systems (MEMS) with its low power consumption and excellent RF characteristics has a potential of creating new, flexible and cost efficient wireless systems for these markets.

In this thesis a set of methods to analyze the characteristics of a novel series resistive contact switch concept are presented. The switch concept is based on the fabrication of a laterally actuated cantilever beam using Deep Reactive Ion Etching (DRIE) and a conformal metal deposition process.

The majority of methods presented are analytical but different modules of CoventorWare® and especially ARCHITECT have also been used for verification and supporting analyses.

The switch concept offers the possibility to fabricate complex switch geometries with few process steps and potentially no stiction problems during release. The resulting cross-section of the fabricated cantilever beam consists of a single crystal silicon core with a metal cladding layer. This makes the beam less sensitive to residual stress in the metal film. The layered beam can also potentially improve characteristics such as switching time. However, the fabrication process has several disadvantages that for instance apply unfortunate limitations to certain geometric dimensions of the switch.

As a result of the lateral actuation configuration, the switch can be incorporated into a coplanar transmission line structure. This offers the possibility to design a switch with good matching to its surrounding circuitry and improved high frequency characteristics.

The switch concept is also compared to the more traditional layered surface micromachining approach.

A chapter presenting a model to estimate the contact resistance is also include, which also functions as an introduction into the complex contact physics for resistive contact MEMS switches.