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Schottky Barrier Contact-Based RF MEMS Switch




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JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, VOL. 17, NO. 6, DECEMBER 2008 1439 Schottky Barrier Contact-Based RF MEMS Switch Brandon Pillans, Member, IEEE, Frank Morris, Prem Chahal, Member, IEEE, Gary Frazier, and Jeong-Bong Lee, Senior Member, IEEE Abstract—This paper presents the design, fabrication, and mea- surement results for a novel Schottky barrier contact-based radio frequency (RF) microelectromechanical systems (MEMS) switch. This Schottky barrier contact allows one not only to operate the RF MEMS switch in a traditional capacitive mode when it is reverse biased but also conduct current in a forward biased state. Forward biasing the switch recombines trapped charges, thus extending the lifetime of the switch. This paper intimately combines MEMS processing with solid-state electronics to produce a truly unique RF device. [2008-0097] Index Terms—Microelectromechanical devices, microwave switches, reliability, Schottky barriers, semiconductor materials. I. INTRODUCTION M ICROELECTROMECHANICAL systems (MEMS) have permeated many commercial and defense systems through the use of accelerometers, ink-jet printer nozzles, and microdisplay devices to name a few [1]. By shrinking traditional components to the microscale, advantages to cost, power, and performance can be realized. However, because these devices are all mechanical in nature and the forces involved are small, reliability becomes a key concern in how quickly the technology can be implemented. For the devices previously mentioned, the reliability has been extensively studied and improved upon such that these components can be found in even the most demanding and critical applications such as automobile airbag deployment sensors. For newer types of MEMS devices such as radio frequency (RF) switches, the reliability is still in question and must be improved and demonstrated for systems to take advantage of the superior performance. RF MEMS switches offer a high-performance low-power low-cost alternative to traditional diode switches [2], but im- proving the reliability of these devices remains of critical importance in accelerating the widespread adoption of this tech- nology. This paper expands upon the brief version presented at the MEMS 2007 conference [3]. Manuscript received April 11, 2008; revised July 25, 2008. Current version published December 4, 2008. Subject Editor C. Hierold. B. Pillans is with Raytheon Company, Dallas, TX 75243 USA, and also with The University of Texas at Dallas, Richardson, TX 75080 USA (e-mail: [email protected]). F. Morris and G. Frazier are with Raytheon Company, Dallas, TX 75243 USA. P. Chahal was with Raytheon Company, Dallas, TX 75243 USA. He is now with Abbott Laboratories, Abbott Park, IL 60064-3500 USA. J.-B. Lee is with the Department of Electrical Engineering, The University of Texas at Dallas, Richardson, TX 75080 USA. Digital Object Identifier 10.1109/JMEMS.2008.2007227 Fig. 1. Areas where trapping occurs in capacitive RF MEMS switches. II. DIELECTRIC CHARGING Dielectric stiction is the primary failure mode in capacitive switches [4] and the failure mode of interest for this paper. High electrostatic fields across the thin dielectric cause charge to tunnel into the dielectric, where it remains trapped for an extended amount of time due to long recombination times. Over time, these charges accumulate and can reach a point at which the voltage ...





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