A ZIPPING TUNABLE CAPACITOR
F. CASSET, P. ROBERT, C. BILLARD, C. MAEDER-PACHURKA, P. L. CHARVET, P. ANCEY, G. BOUCHE, M. AÏD

Introduction
The increasing demand for smaller and more capable portable phones and computers has spawned an explosion of growth in wireless communications technology. For this purpose, micro mechanical devices have been investigated.
For many applications, the tunability of MEMS is a key for challenging the existing antennas, reconfigurable filters or VCO [1].
A variable capacitor can be the tunable component. The demonstration of an above IC MEMS variable capacitor will increase the interest for the MEMS solutions.
This paper reports the study of such an electrostatic tunable capacitor. The actuation mechanisms of the electrostatic structure are detailed: pull-in for initializing the structure, then zipping (induces important electrostatic force) to cover the tuning range.
The Coventor FEM (Finite Element Method) simulation results show theoretically a low pull-in voltage and power consumption, and a large tuning range of capacitance. Theoretical performances are listed.
We present the topology of the first technological demonstrators and the electrical and RF characterizations made on it.
Future technological optimizations needed and perspectives for the zipping tunable capacitance are finally given.