Silicon-Embedding Approaches to 3-D Toroidal Inductor Fabrication

Yu, Xuehong; Kim, Min‐Soo; Herrault, Florian; Ji, Chang-Hyeon; Kim, Jungkwung; Allen, Mark G.

doi:10.1109/jmems.2012.2233718

Cited by 19 publications

(13 citation statements)

References 21 publications

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“…Si-embedded inductors are also an attractive solution for the advanced packaging of ultra-compact power supplies with the passive interposer 24 . There are prior-art studies of etched Si cavities for embedded inductors (wet-etched 25 and dry-etched 26 ) or through-silicon vias (TSV) 24,[26][27][28] . Yu et al 26 reported a Si-embedded inductor using a fabrication process using 3D shadow masks and multiple lithographical exposures with SU-8.…”

Section: Introductionmentioning

confidence: 99%

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Fabrication of 3D air-core MEMS inductors for very-high-frequency power conversions

Thanh

Mizushima²,

Nour

et al. 2018

Microsyst Nanoeng

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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 mm 2 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.

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Section: Introductionmentioning

confidence: 99%

“…The parasitic capacitances between the Cu windings and the Si substrate deteriorates the quality factor and decreases the operation frequency 26,33 . In addition, there is also an eddy-current loss in the Si core 34 .…”

Section: Introductionmentioning

confidence: 99%

Fabrication of 3D air-core MEMS inductors for very-high-frequency power conversions

Thanh

Mizushima²,

Nour

et al. 2018

Microsyst Nanoeng

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“…They have the advantage of no core loss and high frequency operation [21]. Previous works reported on air-core inductors including 2D planar inductors [22], [23], onsubstrate 3D inductors [24], [25], and substrate-embedded 3D inductors [26], [27]. In many air-core inductors, the silicon substrate fully or partially remained, which causes undesired parasitic capacitance and eddy-current losses.…”

Section: Introductionmentioning

confidence: 99%

“…In many air-core inductors, the silicon substrate fully or partially remained, which causes undesired parasitic capacitance and eddy-current losses. Thus, quality factor and operating frequency are reduced [27]. Therefore, in the ideal air-core inductor design, the entire core must be removed.…”

Section: Introductionmentioning

confidence: 99%

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Microfabricated Air-Core Toroidal Inductor in Very High-Frequency Power Converters

Thanh

Nour

Han

et al. 2018

IEEE J. Emerg. Sel. Topics Power Electron.

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Abstract-Miniaturization of power supplies is required for future intelligent electronic systems e.g. internet of things devices. Inductors play an essential role, and they are by far the most bulky and expensive components in power supplies. This paper presents a miniaturized microelectromechanical systems (MEMS) inductor and its performance in a very high frequency (VHF) power converter. The MEMS inductor is a siliconembedded air-core toroidal inductor, and it is constructed with through-silicon vias, suspended copper windings, silicon fixtures, and a silicon support die. The air-core inductors outperform the silicon-core inductors with higher quality factor at higher frequency. This is verified by small-signal measurements. A 20-turn air-core inductor achieved an inductance of 44.6 nH and a quality factor of 13.3 at 33 MHz, while a silicon-core inductor with the same geometry has a quality factor of 9 at 20 MHz. A DC-DC class-E boost converter is designed and implemented using the fabricated MEMS air-core inductor and a highperformance 65 V gallium nitride field effect transistor. The VHF converter achieved a peak efficiency of 78 % at the input voltage of 6.5 VDC. The MEMS inductor can carry 1 A RMS AC current at 33 MHz and delivers 10.5 W to the output.Index Terms-Microelectromechanical systems, inductor, DC-DC power converters, zero voltage switching, gallium nitride.

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