Fully integrated micromachined inductors with electroplated anisotropic magnetic cores

Batch fabricated, integrated magnetic devices incorporating magnetically anisotropic cores are investigated. These devices are realized using low temperature processes and electroplating techniques. Three different geometries of inductors, each possessing two core materials, permalloy (NiFe) and supermalloy (NiFeMo), are presented. The cores have been rendered magnetically anisotropic by application of a magnetic field during electrodeposition, resulting in an easy and hard axis orientation. In addition, some cores consist of a two-layer electrodeposit separated by a polyimide film lamination. At low frequencies (less than 100 kHz), the easy axis devices have higher inductances than the hard axis devices. However, the hard axis devices have better performance at higher frequency due to a far less steep falloff of material permeability as a function of frequency in the hard direction.