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 200nm lines and 300nm spaces with clear-cat features were fabricated.