A new toroidal-meander type integrated inductor with a multilevel meander magnetic core

A novel toroidal-meander type integrated (TMTI) inductor with a multilevel meander magnetic core has been designed, fabricated, and integrated onto a silicon wafer. In a conventional inductor, conductor wires are wound around magnetic cores. By switching the roles of conductor wire and magnetic core, i.e., by `wrapping´ a magnetic core around a conductor wire, the same effect can be realized in a planar geometry. This geometry has been implemented using multilevel metal interconnection schemes, by interlacing a meander planar conductor with a multilevel meander magnetic core. The total inductor size is 4 mm×1.0 mm, the coil has 30 turns, and the magnetic material used was electroplated nickel(81%)-iron(19%) Permalloy. An inductance of 30 nH/mm² was achieved at a frequency of 5 MHz. The fabrication sequence of this inductor structure is entirely compatible with post-processing of standard bipolar and CMOS circuitry, as well as the fabrication of multichip module substrates, thus enabling the integration of the inductor structure with control circuitry for applications such as filters, sensors, magnetic microactuators, and low-power voltage converters