Characterization, modelling and performance evaluation of CMOS integrated multielectrode tunable capacitor (MTC)

This paper describes the characterization, modelling and evaluation of multielectrode micromechanical structures. Firstly, results of interferometric inspection and electrostatic measurements of fixed-fixed beams with various anchor designs are presented. These data, combined with finite element (FE) analysis of anchor compliance, are used to extract the elastic modulus and residual stress for a thin film aluminium structural layer. Secondly, a multielectrode tunable capacitor (MTC) is presented. The device consists of a suspended top plate and split bottom electrode. The 'leveraged bending' method is examined for extending the tuning range (TR) of such a capacitor. FE simulation of the MTC up to pull-in instability for each drive electrode configuration indicates a TR varying from 1000% to 40% in the range of stress from 0 to 45 MPa. An analytical model for the pull-in voltage of the MTC taking into account partial and/or multielectrode configuration, non-ideal anchors, field fringing and plane strain is presented. The analytical and FE simulations are validated with measured data.