Fabrication of close-packed non-circular nanomagnetic pattern using low energy self-limiting ion-milling process

We describe a low energy glow discharge process using a reactive-ion etching system that enables non-circular device patterns, such as squares or hexagons, to be formed from the precursor arrays of uniform circular openings in polymethyl methacrylate (PMMA), defined by electron beam lithography. This new technique is of a particular interest for bit-patterned magnetic recording medium fabrication, where square magnetic bits result in improved recording system performance. The process of generating close packed square patterns by self-limiting ion-milling (SLIM) are investigated. Results are statistically analyzed to establish optimization. Fabrication of non-circular nanostructures has been demonstrated. Dense magnetic arrays formed by electrochemical deposition, evaporation and sputtering deposition over SLIM-formed moulds are accomplished. Applications in master production technologies such as ion beam proximity lithography and nanoimprint template manufacturing are evaluated. New technology of magnetic patterning using low energy ion irradiation is under investigation. Helium ions strike a cobalt oxide layer to remove oxygen from a non-magnetic oxidized material, resulting in the recovery of magnetic properties of cobalt in an exposed area. The thin film of the cobalt layer turning from cobalt oxide by 120eV helium irradiation has been demonstrated. Pattern fabrication and investigation on multilayer irradiation are future work.