Design and Analysis of a MEMS Variable Capacitor

We present the design and analysis of a MEMS variable capacitor coupled to thermal actuators. The variable capacitor is composed by two main components: 1) the capacitor built by two squared plates, which one plate is mechanically fixed to the substrate and the other is a moving plate having mechanical suspensions (springs) connected from each corner of it to the substrate, and 2) a set of thermal actuators that push the moving plate away from the substrate. Depending on the power applied on the thermal actuators, these would push up the variable plate from its sides, while the suspension pulls the plate down to the substrate for equilibrium. This work includes the design fabrication steps using PolyMUMPSTM process, and provides tables for the resulting values of the variable capacitors. The results accomplished using COVENTORWARETM software show that the variable capacitor has potential for automatic compensation of capacitances and for integration into frequency oscillators and filters.