Robust Design of RF-MEMS Cantilever Switches Using Contact Physics Modeling

Abstract

This paper presents the robust design optimization of an RF-MEMS direct contact cantilever switch for minimum actuation voltage and opening time, and maximum power handling capability. The design variables are the length and thickness of the entire cantilever, the widths of the sections of the cantilever, and the dimple size. The actuation voltage is obtained using a 3-D structural-electrostatic finite-element method (FEM) model, and the opening time is obtained using the same FEM model and the experimental model of adhesion at the contact surfaces developed in our previous work. The model accounts for an unpredictable variance in the contact resistance resulting from the micromachining process for the estimation of the power handling. This is achieved by taking the ratio of the root mean square power of the RF current ("signal") passing through the switch to the contact temperature ("noise") resulting from the possible range of the contact resistance. The resulting robust optimization problem is solved using a Strength Pareto Evolutionary Algorithm, to obtain design alternatives exhibiting different tradeoffs among the three objectives. The results show that there exists substantial room for improved designs of RF-MEMS direct-contact switches. It also provides a better understanding of the key factors contributing to the performances of RF-MEMS switches. Most importantly, it provides guidance for further improvements of RF-MEMS switches that exploit complex multiphysics phenomena.

Design, optimization and simulation of a low-voltage shunt capacitive RF-MEMS switch

“…Since every geometric parameter could be set with three different values, it will be tedious to simulate all their possible combinations (3 4 = 91 times). Therefore, a proper optimization technique is necessary here; it is also a general problem to be encountered by most RF-MEMS switches' design (Shalaby et al 2009;Philippine et al 2013). The only difference from each work could be the optimized responses (such as switching speed, power handling capability or RF performance) (Shalaby et al 2009;Badia et al 2012) or geometric design (shapes or dimensions) (Peroulis et al 2003;Gong et al 2009).…”

“…Taguchi defines robustness as the "insensitivity of the system performance to parameters that are uncontrollable by the designer" (Taguchi et al 1987). A robust design incorporates this concept of robustness into design optimization and aims at achieving designs that optimize given performance measures while minimizing sensitivities against uncontrollable parameters using different approaches, such as signal to noise ratio (Shalaby et al 2009). The Taguchi approach itself can be utilized to determine the best parameters for the optimum design configuration with the least number of analytical investigations.…”

“…In order to monolithically integrate these RF-MEMS switches with active CMOS circuitry, an additional voltage-upconverter or an external off-chip circuit is needed ), which will make the whole chip larger, more complex, and consume more power. Chan et al and Goldsmith et al indicated that a high actuation voltage also may lead to a shorter lifetime for capacitive RF-MEMS switches which use dielectric layers for isolation (Shalaby et al 2009). Diverse RF-MEMS switch designs have been proposed by various researchers to reduce the actuation voltages.…”

Integrated modeling of nonlinear dynamics and contact mechanics of electrostatically actuated RF-MEMS switches

“…In reality, both the contact surfaces of the cantilever and the substrate are rough surfaces [12]. By that reason, when the switch is actuated, only a few asperities make contact with the bottom substrate.…”

Design optimization of RF-MEMS switch considering thermally induced residual stress and process uncertainties

“…For the robust design optimization, Shalaby et al have proposed strength Pareto evolutionary algorithm for RF MEMS cantilever switches [19]. The genetic algorithms have been used for the robust design of MEMS accelerometer in [20].…”