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

J. K. Luo, M. Lin, Yong Qing Fu, L. Wang, Andrew Flewitt, S. M. Spearing, Norman Fleck, William Milne

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)139-146
JournalSensors and Actuators A: Physical
Issue number1
Publication statusPublished - 8 Nov 2006


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