A novel integrated power inductor in silicon substrate for ultra-compact power supplies

A novel silicon-based inductor, power inductor in silicon, or PIiS, has been proposed and experimentally demonstrated. The PIiS is fabricated at wafer level using a silicon molding micromachining technique, in which 200 ¿m thick copper windings are embedded into a silicon substrate and both sides of the substrate are capped with a polymer-magnetic power composite. Through-silicon vias (TSVs) and copper routings are also added so that a PIiS can be directly used as a surface mountable packaging substrate. A 3 × 3 × 0.6 mm³ PIiS with a measured inductance of 390 nH has been fabricated. The Q factor of this PIiS is 10 at 6 MHz. An ultra compact buck converter has been made by surface mounting off-shelf power ICs and capacitors on a PIiS. The buck converter is 3 × 3 × 1.2 mm³, which has successfully delivered 500 mA at 1.8 V with an 80% efficiency at 6 MHz.