Fabrication of magnetic rings for high density memory devices

A new technique has been developed to fabricate magnetic ring elements. The technique is based on pre-patterning of silicon ring structures and subsequently epitaxial growth of copper-cobalt-copper sandwich film on top of silicon rings. In contrast to conventional methods of making magnetic elements, no damage to the magnetic layer structure is introduced by the patterning process. Unlike conventional magnetic structures, there are a number of challenges in patterning ring geometry by electron beam lithography and by reactive ion etching. Electron beam lithography process has been optimised for patterning ring structures of sub half micrometer dimension. Both conventional RIE and deep RIE techniques have been tried for transferring resist ring structure to silicon substrates. Large arrays of magnetic rings have been fabricated by the prepatterning techniques. Magnetic measurement by MOKE method has demonstrated the new onion state for magnetic switching, which is in agreement with computer simulation results. (C) 2002 Elsevier Science B.V. All rights reserved.