Block copolymer nanolithography for the formation of patterned perpendicular media.

摘要

Bit patterned perpendicular media have the potential to increase the density of magnetic recording beyond what can be achieved by granular media. Self assembling diblock copolymers are of interest as templates for patterned media, as they potentially provide a low cost fabrication route. A method to fabricate the desired pattern using cylinder forming diblock copolymers of (PS-b-PMMA) as template is reported. Upon phase separation, hexagonally packed cylinders of the minority phase (PMMA) surrounded by the continuous majority phase (PS) are obtained.;Synthesis of block copolymer was carried out in collaboration with Dr. Jimmy May's group at the Oak Ridge National Laboratory by anionic polymerization method. The block copolymer used during the study contained 67% PS and 33% PMMA. The fabrication route consisted of various steps. The processing sequence began with spin coating the block copolymer on a suitable substrate, followed by annealing the block copolymer thin film in vacuum to orient it perpendicular to the substrate. Block copolymer templates were obtained by glacial acetic acid treatment or UV irradiation which opened the pores in the block copolymer thin film. Nickel was electrodeposited in the block copolymer templates and this pattern was then transferred onto the underlying substrate by combining reaction ion etching and ion milling. Various substrates were tried for the fabrication of block copolymer templates, these include, H-terminated Si, carbon coated commercial hard drive media, ITO, Cu, Ni, Ta and Pt.;During the course of this study surface characterization was carried out with the help of atomic force microscope (AFM), scanning electron microscope (SEM), grazing incidence small angle scattering (GISAXS) and x-ray reflectivity (XRR). Elemental analysis was carried out with the help of energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS).