Design of toroidal inductors using stressed metal technology

This paper presents design, fabrication and characterization of three-dimensional (3-D) toroidal inductors using a stressed metal technology developed at Purdue University. The fabricated 31-turn toroidal inductor on high-resistivity silicon substrate shows inductance value of 25.4 nH and peak quality factor of 14.2. Because of the arc deployment of inductor turns, it is found that a sufficiently narrow turn-to-turn gap is essential to achieve high inductance value. In addition, it is found that, even for toroidal inductors, the substrate effects are the dominant loss mechanism at high frequencies and should be suppressed in order to obtain high values of the quality factor.