High inductance density in CMOS-compatible magnetically integrated 3D microinductors for radio-frequency applications

Area of Science:

• Microelectronic Engineering
• Materials Science
• Electrical Engineering

Background:

• On-chip inductors are crucial for integrated radio-frequency (RF) electronics.
• Planar inductors suffer from low inductance density, limiting miniaturization and efficiency.
• Existing inductors occupy large chip areas, hindering the development of compact systems.

Purpose of the Study:

• To introduce a novel 3D rolled-up, magnetically integrated microinductor technology.
• To overcome the limitations of planar inductors by achieving higher inductance density.
• To enable more compact and efficient RF systems-on-chip.

Main Methods:

• Fabrication of 3D rolled-up microinductors using strained layers and magnetic thin films.
• Exploitation of a superlinear scaling law (D ∝ l^2.4) through 3D winding.
• Development of a wafer-scale, CMOS-compatible self-assembly process.

Main Results:

• Achieved record-high inductance density of 8333 nH/mm² at 0.55 GHz, over two orders of magnitude higher than planar inductors.
• Demonstrated a 3D geometry that intensifies local fields and flux linkage while reducing leakage.
• Successfully rolled 10 mm of planar conductors into ~240 μm-diameter microcoils.

Conclusions:

• The 3D magnetically integrated microinductors offer a significant advancement for RF electronics.
• High inductance density, low substrate losses, and GHz operation are suitable for compact RF systems-on-chip.
• This technology is poised to benefit next-generation Internet of Things (IoT), 5G, and 6G applications.