High density plasma etching of NiFe, NiFeCo and NiMnSb-based multilayers for magnetic storage elements

Magnetic multilayer thin films based on the Giant Magnetoresistive effect a re the basis of extremely high density (> 10 Gbit in.(-2)) data storage sys tems. A challenge to continue the rapid growth in bit density is the abilit y to pattern sub-micron features in materials such as Ni0.8Fe0.2, NiFeCo al loys and NiMnSb. Conventional reactive ion etching methods are generally un able to successfully etch these materials because of low volatility of the etch products. We have found that Inductively Coupled Plasma sources operat ing with ion densities several orders of magnitude higher than RIE provide etch rates of 700 Angstrom min(-1) for NiFe and NiFeCo in Cl-2/Ar discharge s, and > 10,000 Angstrom min(-1) for NiMnSb in SF6/Ar. Sub-micron features with smooth, vertical sidewalls are obtained using SiO2 or SiNX masks. Phot oresist is generally found to be an unsuitable mask under high density plas ma conditions. (C) 1999 Elsevier Science B.V. All rights reserved.