Sputter deposition of 45% Ni-55% Fe for high moment top pole applications

Abstract

We present the properties of dc magnetron sputter-deposited 45% Ni-55% Fe. Optimal magnetic properties obtained in 1.4 μm films were: 4πMs∼16.4 kG, Hce∼3.7 Oe, Hch∼0.8 Oe, Hk∼9.6 Oe, at a deposition rate of 29 Å/s. A linear designed experiment revealed that: higher gas pressure significantly lowers both Hce and Hk; higher (rf) substrate bias increases α90 and Hch, while decreasing Hk; and higher substrate magnetic field worsens Hch and α90. Augmentation of the experimental matrix and analysis of higher order terms implied that a combination of intermediate pressure and small bias provides optimal magnetic properties. From x-ray diffraction, the 45–55 NiFe is fcc, with lattice parameter 3.578–3.584 Å, in fair agreement with the bulk value of ∼3.585 Å. Grain sizes in the range 150–180 Å were estimated. Analysis of the (111): (200) peak intensity ratio showed that higher substrate bias or lower pressure both significantly enhance the (111) texture. Correlation was observed between the magnetics and the crystalline texture; less [111] texture gives lower coercivity. Data on 2000 Å films for seedlayer applications are also presented.