Hole mask colloidal lithography on magnetic multilayers for spin torque applications

Abstract

We demonstrate the fabrication of metallic nano-contacts on magnetic multilayers using a Hole Mask Colloidal Lithography technique (HCL) based on Polystyrene spheres. The method applies PMMA as a sacrificial layer upon which a hole pattern is formed after lift- off of the spheres. An Au layer functions as a hard mask for the PMMA and the PMMA subsequently masks the SiO2 during its etching. The resulting pattern is a dense collection of randomly located nano-holes through a SiO2 film. Final devices are made using traditional photolithography to define a 600 nm circular mesa with about 3 to 4 nano-holes per device, and patterning of a metallic top contact.