The paper presents the realization and characterization of micro-inductors with core with active cooling capability for future integrated DC/DC converter solutions operating with wide bandgap semiconductors at high temperatures with high power densities. The cores are fabricated backend-of-line compatible by filling cavities in silicon wafers with soft magnetic iron particles and their subsequent agglomeration to rigid, porous 3D microstructures by atomic layer deposition. Wafer processing is presented as well as measurement results at up to 400 ∘C operating temperature in comparison to of-the-shelf inductors. Using a DC/DC converter operating at 25 MHz switching frequency efficiencies of 81 to 83% are demonstrated for input voltages between 5 V and 12 V. It is shown that the temperature of the novel micro-inductors decreases if an air flow through its porous core is applied. This feature could be especially helpful for the realization of resonant power converters with larger temperature stress to passive components.
Keywords: PowderMEMS technique; active cooling; atomic layer deposition; high temperature; integrated DC/DC converter; integrated inductances; magnetic core; porous structure.