Fabrication of 3D Air-core MEMS Inductors for High Frequency Power Electronic Applications

Hoà Lê Thanh, Io Mizushima, Yasser Nour, Peter Torben Tang, Arnold Knott, Ziwei Ouyang, Flemming Jensen, Anpan Han*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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We report a fabrication technology for 3D air-core inductors for small footprint and very-high-frequency power conversions. Our process is scalable and highly generic for fabricating inductors with a wide range of geometries and core shapes. We demonstrate spiral, solenoid, and toroidal inductors, a toroidal transformer and inductor with advanced geometries that cannot be produced by wire winding technology. The inductors are embedded in a silicon substrate and consist of through-silicon vias and suspended windings. The inductors fabricated with 20 and 25 turns and 280-350 μm heights on 4-16 mm2 footprints have an inductance from 34.2 to 44.6 nH and a quality factor from 10 to 13 at frequencies ranging from 30 to 72 MHz. The air-core inductors show threefold lower parasitic capacitance and up to a 140% higher-quality factor and a 230% higher-operation frequency than silicon-core inductors. A 33 MHz boost converter mounted with an air-core toroidal inductor achieves an efficiency of 68.2%, which is better than converters mounted with a Si-core inductor (64.1%). Our inductors show good thermal cycling stability, and they are mechanically stable after vibration and 2-m-drop tests.
Original languageEnglish
Article number17082
JournalMicrosystems & Nanoengineering (Online)
Number of pages9
Publication statusPublished - 2018


  • MEMS inductor
  • PwrSoC
  • TSVs
  • Very high frequency
  • 3D


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