Ultramicro fabrications on Fe-Ni alloys using electron-beam writing and reactive-ion etching

A novel reactive-ion-etching (RIE) method useful for ferromagnetic material of Permalloy (80%Ni-4.5%Mo-Fe) has been developed. This method involves rf plasma of a gas mixture NH₃-CO aimed at the formation of volatile transition metal carbonyls. A maximum etching rate of 35 nm/min and highly anisotropic etching was obtained. The etching selectivity ratios of Permalloy to SiO₂ or Si were about 10 or 4, respectively. High-resolution electron-beam writing was followed by the RIE process on the Permalloy films. To achieve high-resolution electron-beam writing, amorphous carbon film was placed between the resist layer and SiO₂ film overlaid on the Permalloy film. By this method, nanostructures of Permalloy stripes of 200 nm lines and 300 nm spaces with clear-cut features were fabricated