Anisotropic Ni–Fe–B films with varying alloy composition for high frequency magnetics on silicon applications

Abstract

An electroless nickel-iron alloy deposition process utilizing an external magnetic field was studied to achieve varying nickel and iron compositions for the specific high frequency application range. High anisotropy, low coercivity and high saturation flux density values were achieved which show significant improvements appropriate for high frequency magnetics on silicon applications. It has been shown that higher Fe content films can be achieved by increasing the DMAB concentration. The magnetic, electrical and structural characteristics of these application specific films with different Fe content were reported. The increased resistivity of the films reduces the eddy current losses whereas the permeability studies suggests high frequency applicability of the thin films as core material in magnetics on Si applications. The micro-structural analyses suggested that the deposits are nano-crystalline in nature with grain sizes below 33 nm resulting in low coercivity values in the films. The pH value is compatible with standard photoresists used in silicon based microfabrication processes.