Effect of etch holes on the capacitance and pull-in voltage in MEMS tunable capacitors

This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Microelectromechanical systems (MEMS) tunable capacitors, switches or actuators are widely applied in wireless communication systems. In the fabrication process etch holes are used to release the sacrificial layer with relatively large structures, which obviously affects the performance of devices. However, most researchers neglect this effect during their designing of the capacitors, switches or actuators. This article presents the theoretical calculation of the capacitance of tunable capacitors with etch holes, and analyses the deviation of the capacitance and pull-in voltage with different parameters such as the length of the plates w, the length of the etch holes w h , the air gap between the two plates d, and the number of the etch holes. To validate the theory in this article, a tunable capacitor was fabricated by surface micromachined technology. The theoretical results compare well with the experimental results. 1. Introduction Radio frequency (RF) components fabricated by microelectromechanical systems (MEMS) technology such as switches, inductors, capacitors, phase shifters, oscillators and resonators are utilised in today's wireless communication systems. Among these devices, the tunable capacitor plays an important role in RF circuits used in or as on-chip matching networks, passive filters, voltage-controlled oscillators, power amplifiers, radio transmitters and other tuning circuits for electrostatic actuation and sensing. The parallel plate capacitor driven by electrostatic force is one of the most common devices