MEMS based digital variable capacitors with a high-k dielectric insulator

Luo, J. K., Lin, M., Fu, Yong Qing, Wang, L., Flewitt, Andrew, Spearing, S. M., Fleck, Norman and Milne, William (2006) MEMS based digital variable capacitors with a high-k dielectric insulator. Sensors and Actuators A: Physical, 132 (1). pp. 139-146. ISSN 0924 4247

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Official URL: http://dx.doi.org/10.1016/j.sna.2006.04.025

Abstract

A novel MEMS based digital variable capacitor was designed and fabricated. The device consists of a multi-cantilever (or bridge) with variable length, suspended over a bottom electrode. By applying a voltage between the electrodes, the electrostatic force pulls the beams in one-by-one, realizing a digital increase in capacitance. A high-k dielectric HfO2 is also introduced to increase the capacitance value and tuning range. These devices were fabricated by a four-mask process, and electrical tests have confirmed the stepwise increase of the capacitance with bias. However it was found that it is difficult to pull-in more than 10 cantilevers and most of the cantilevers remained on the substrate when the bias is off. Charge injection from the pulled-in electrode into the insulator increases the pull-in voltage drastically, and prevents pulling-in more cantilevers. Trapped charges in the insulator produce an electrostatic force and keep the cantilever stuck on the substrate.

Item Type: Article
Uncontrolled Keywords: MEMS; Digital variable capacitor; High-k dielectric; Charge injection
Subjects: F200 Materials Science
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Becky Skoyles
Date Deposited: 27 Mar 2015 09:42
Last Modified: 24 Oct 2017 08:54
URI: http://nrl.northumbria.ac.uk/id/eprint/21874

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