The ever reducing size of mobile electronic equipments combined with the increase in the number of functionalities force the power conversion systems (DC-DC converters) to adapt to the following constraints: miniaturisation, improved efficiency, reliability and minimum cost. Passive components (inductors, capacitors) assuring storage and filtering are the bulkiest components of the systems. The way to reduce the size of passive components is to increase the systems operating frequencies. In the MHz range, the integration of microinductors, microcapacitors on silicon chip is possible with microfabrication techniques. However, the challenge nowadays for these micro-components is to achieve at the same time: very high specific values and low losses to provide over 90% efficiency of the overall converter.

In the group ISGE, we develop designs and technologies for integrated passive components. The integration of new materials (magnetic and dielectrics) in thin films is one of the key elements to realize passive micro-components with high performance.

Micro-inductors

The developed technologies for micro-inductors are:

• Electrodeposition of thick copper wires (1 or 2 levels).
• Electrodeposition of magnetic materials: NiFe, NiCoFe, for the magnetic core.
• Thick photoresist to provide insulation between the different levels.

Image a) and Image b)

3D capacitors

The tridimensionnal capacitors developed contain:

• High aspect ratio pore networks etched in silicon by DRIE (Deep Reactive Ion Etching) to provide a high specific surface for electrodes.
• Deposition (CVD) of dielectric materials : SiO₂, Si₃N₄, ZrO₂

Integrated filter (L+C)

Always for DC-DC converter applications, we are developing solutions to integrate filters on silicon : it consists in realizing the integrated capacitor and the micro-inductor on the same substrate.