Wafer-level fabrication of high-power-density MEMS passives based on silicon molding technique

This paper reports a novel MEMS fabrication technology that can integrate toroidal inductors or transformers into silicon substrate. Such toroidal windings are realized by electroplating copper to form 200 μ-deep through-silicon vias (TSVs) and 60 μ-thick copper lines on both sides of the silicon substrate. Meanwhile, the magnetic core is formed by filling deep silicon trenches with a composite of magnetic powders and a polymer. A 13 × 13 × 0.32 mm³ toroidal inductor with a measured inductance of 160 nH has been fabricated. The Q factor of this inductor is 10.5 at 14 MHz. Toroidal transformers with Polyimide as the dielectric material between stacked windings were also fabricated.