High Temperature Magnetic Cores Based on PowderMEMS Technique for Integrated Inductors with Active Cooling

Abstract

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.

Unleashing the Performance of Self‐Rolled‐Up 3D Inductors via Deterministic Electroplating on Cylindrical Surfaces

“…Figure a compares the performance, inductance density (L/area) vs Q/area, of the S‐RuM power inductors with conventional state‐of‐the‐art (SoA) micro‐inductors with similar sizes, frequencies, and application targets. [ 58–72 ] By this figure of merit, S‐RuM Cu plated inductors achieved very high Q per area due to resistance improvements of over 10x. The Q value of the 2‐cell, 5‐turn S‐RuM inductors (plotted in green) improved from 2 to 15 without changing the physical areal footprint of 0.15 mm 2 , allowing this device design to reach a higher Q per area than all other reported micro‐inductors.…”

“…Benchmark of S‐RuM electroplated inductors with conventional state‐of‐the‐art (SoA) inductors. a) Benchmark chart of L/area vs Q/area for three types of S‐RuM inductors against other SoA micro‐inductors recently reported in the literature: [ 58–72 ] (green) 2‐cell, 5‐turn, Cu plated devices; (yellow) 4‐cell, 15‐turn, Cu plated devices; (red) 4‐cell, 10‐turn, Cu shell and magnetic core plated devices (circle for control/unplated, star for plated). b) Comparison of S‐RuM devices of the same geometries with and without electroplating: (green) 2‐cell, 5‐turn, Cu plated devices showing significant resistance drop; (yellow) 4‐cell, 15‐turn, Cu plated devices showing significant resistance drop; (red) 4‐cell, 5‐turn, and (blue) 4‐cell 10‐turn, Cu shell and magnetic core plated devices, showing both significant resistance drops and inductance increases (circle for control/unplated, triangle for plated).…”

Towards Robust Thermal MEMS: Demonstration of a Novel Approach for Solid Thermal Isolation by Substrate-Level Integrated Porous Microstructures

“…Finally, the wafers are cleaned of any unwanted powder residues and are ready for further processing under standard MEMS cleanroom conditions. In previous work, the use of PowderMEMS structures for energy harvesting and zero-powder wakeup [ 18 , 19 ], permanent micromagnets and magnetic position detection [ 20 , 21 ], and the creation of liquid-cooled microscale inductor cores [ 22 ] has been presented.…”