Gradient growth of fcc and bcc phase within FexNi1−x (50 < x < 75) films during direct-current wafer electroplating

Abstract

In order to investigate the performance of Fe-Ni magnetic cores within embedded inductor in 3D package, a series of Fe-Ni films with compositions ranging from 15 wt% to 80 wt% iron were electrodeposited on 8-inch silicon wafer. The uniformity on brightness, phase structure and grain size of Fe-Ni magnetic films were investigated through SEM (scanning electron microscopy) and XRD (X-ray diffraction). A gradient growth behavior of fcc (face-centered cubic) and bcc (body-centered cubic) phase was revealed when Fe content ranges 50–75 wt% within Fe-Ni films, which can be attributed to the slightly faster growth rate of fcc phase. As also revealed in TEM (transmission electron microscope) observation, the fcc phase gradually spread over bcc phase region during the electroplating process, and formed an interface with a slight tilt angle to the substrate on the thickness direction. Several methods, such as increasing solution stirring, temperature or decreasing the current density, were proposed to restrain the gradient growth behavior of Fe-Ni film in wafer level.