Multi-pulse electrodeposition of soft magnetic thin film Co-P for embedded inductor application

Electrodeposited Co-P thin film has recently attracted a lot attention due to its good high-frequency performance, large magnetic susceptibility, relatively high resistivity and growth rate. Co-P soft magnetic films can be synthesized by either direct current or pulse current plating. The effects of the pulse current on the properties of the electrodeposited Co-P film have not been fully investigated so far. In this study, we synthesized both amorphous and nanocrystalline Co-P films on copper foil from two kinds of fresh solutions by multipulse electrodeposition. We mainly investigated the effects of the negative average current density on the film composition, crystalline structure and surface morphology of the Co-P films deposited on copper foil. The experimental results showed that without the electrolyte change, the phosphorous content could be greatly changed by just varying the negative pulse current density, which provided a flexible tuning knob for Co-P films. The surface morphology of the Co-P films varied with the phosphorous content and the pattern of the film growth was the nodular growth. In addition, with an external magnetic field applied during the electroplating, the Co-P films on copper-coated Si wafer showed a good soft magnetic property (H_c is 1-2 Oe) and high permeability (∼700).