Pulse reverse plating for integrated magnetics on Si

Thin film microtransformers have been fabricated on silicon with Ni ₄₅Fe₅₅ as a core material. Fractal/dendritic growths are observed in the patterned cores in DC electroplating due to the enhancement of localized current density at defect/nucleation sites. A 'pulser' device was made in house to produce forward and reverse current of the required amplitude for a particular duration. The combination of a low amplitude long (millisecond) forward pulse and a short (microsecond) high-amplitude reverse pulse gave dendrite-free plated cores with a uniform thickness and alloy composition over a 3D topology of a microrough substrate surface. Finally, we characterized the material in situ by small signal electrical measurements, and with MOKE hysteresis loops measured on a complete device.