In many RF MEMS applications, currents are confined to theoutermost portions of conductors due to the skin effect.Conductors consisting of epoxy cores coated with metal areappropriate to consider for these applications, and in manyinstances are easier to fabricate than their solid-metal-corecounterparts. As an example of this approach, this paper reports athree-dimensional, high-aspect-ratio, high Q-factor, solenoid-typeRF inductor. The conductors of this inductor are fabricated usingSU8 epoxy cores and subsequent metal electrodeposition. TheSU8 core approach allows for relatively simple formation ofextremely high aspect ratio columns for inductor sidewalls. Inaddition, an SU8 bridge fabrication technique has been realizedusing a double exposure and single develop scheme. A single,vialess metallization is then used to form the conducting paths ofthe inductor. By combining these techniques, epoxy-core RFinductors have been fabricated and tested. A single turn inductorthat is 900μm in height and has a 600μm wide air-core area showsa maximum Q-factor of 84 and an inductance of 1.17nH at2.6GHz.
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