Fraunhofer Institute for Silicon Technology
Fraunhofer Institute for Silicon Technology

Microcoils

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Integrated inductors with soft magnetic cores based on powder MEMS technology face the challenge of efficiently serving high-frequency applications (1-100 MHz). Traditional methods reach their limits in terms of power density and operating temperatures (up to 400°C). The need to combine compact design with high efficiency is crucial for applications such as smart homes, IoT, and the multimedia consumer market.

The Powder-MEMS technology developed at Fraunhofer ISIT offers innovative solutions for the production of inductors and transformers on substrates (e.g., silicon, FR4). Using atomic layer deposition (ALD), soft magnetic particles (diameter 1-20 µm) are agglomerated in cavities and consolidated with a thin dielectric layer (50 nm). This enables almost loss-free energy transfer and reduces eddy currents.

  • Inductor design process: High degree of freedom
  • Performance: Optimized for fast switching applications
  • Temperature operating range: Up to 400°C
  • Back-end-of-line compatible process: Facilitates integration
  • Good integration options: e.g., inductance + GaN HEMT on the same substrate

PowderMEMS Use Case: Microcoils in a DC/DC converter

  • Development and investigation of microcoils (80-200nH) for high-frequency applications (1-80MHz)
  • Commissioning of a DC/DC converter (20 MHz) with microcoil
  • Goal: Integration solution for coil and other components

    • Power density: Maximization of efficiency
    • Reduction of parasitic sizes: Optimized cooling
    • “Power supply on-a-chip”: Compact solutions
    • Optimized coil/transformer designs: Improvement of overall performance

  • Efficient step-up converter: Proof-of-concept with GaN transistor and switching frequency of 20MHz
  • Coil sample P04: L=150 nH and R=0.6 Ω @ 20 MHz
  • Power up to 20 W: High measured efficiency
  • Comprehensive characterization: SEM investigations and FEM simulations (software: Comsol Multiphysics)

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