Study of air-suspended RF MEMS inductor configurations for realizing large inductance variations

The configurations of the following three types of high-Q air-suspended RF MEMS inductors (in particular, their potentials) are studied to identify the configuration that would yield large inductance variations: an inductor with two angularly meandered lines, a spiral inductor with patterned shields of different areas, and a spiral inductor with metallic frames of different sizes. The potentials of MEMS inductors fabricated on high-resistivity Si substrates are experimentally determined. The inductance of the spiral inductors changes by at most 23% when the shield area or the frame size in the inductors is changed. On the other hand, the inductance of the meander-type inductor changes by 108% (from 2.65 nH to 5.50 nH) because of the large change in the current loop area. The configuration of the meander-type inductor is thus considered suitable for realizing an RF MEMS variable inductor with large inductance variations.