Integrated high-inductance three-dimensional toroidal inductors

Abstract

Fabrication, characterizations, and modeling of three-dimensional high-inductance value toroidal inductors are presented. The effect of substrate and number of turns on toroidal inductors with 16, 31, and 62 turn fabricated using prestressed metals are investigated. A 62-turn inductor on high-resistivity Si substrate has an inductance value of 81 nH, a self-resonance frequency of ∼2 GHz, and a peak quality factor (Q) of ∼10. It is found that the substrate loss is detrimental to the quality factor of toroidal inductors at high frequencies and should be suppressed by using high-resistivity substrate or SU-8 coated Si substrate in order to obtain high values of the quality factor. In addition, reducing turn-to-turn gap in toroidal inductors results in higher mutual couplings among the inductor turns and thus achieving high-inductance values. Integrated high-inductance value, high-Q inductors can be used in integrated switching power supplies, radio frequency (rf) and intermediate frequency filters, energy conversion circuits, and as on-chip rf chokes in rf integrated circuits.