Low-Gas-Pressure Deposition of Co-SiO₂ Granular Films by Reactive Sputtering Using CoSi Alloy Target

Abstract

  We propose a technique for low-gas-pressure (0.6 Pa) deposition of a granular film consisting of Co-based metallic grains and stoichiometric SiO₂ grain boundaries by using reactive sputtering. As a typical example, we experimented in forming Co-SiO₂ granular films by using dc magnetron sputtering with Ar+O₂ mixed gas with a Co_92.3Si_7.7 (at%) alloy target. Detailed analyses of the composition, microstructure, and magnetic properties of the granular films revealed that: (1) a high deposition rate of 3.4 nm/s was realized under a Si-selective oxidization condition of the surface of the CoSi alloy target. (2) The granular film with an O/Si composition ratio of 2 was successfully achieved under the selective oxidization conditions. (3) c-plane-oriented Co grains with SiO₂ grain boundaries were formed on a Ru underlayer. (4) The low-gas-pressure process made it possible to enhance the columnar grown of Co grains without tapering off. These results suggest that the low-gas-pressure process will be effective in improving corrosion and impact resistance even for the current mass-produced perpendicular magnetic recording media with CoPtCr (-SiO₂, -TiO₂) granular materials.