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

Abstract

Magnetic multilayer thin films based on the Giant Magnetoresistive effect are the basis of extremely high density (>10 Gbit in. −2) data storage systems. A challenge to continue the rapid growth in bit density is the ability to pattern sub-micron features in materials such as Ni 0.8Fe 0.2, NiFeCo alloys and NiMnSb. Conventional reactive ion etching methods are generally unable to successfully etch these materials because of low volatility of the etch products. We have found that Inductively Coupled Plasma sources operating with ion densities several orders of magnitude higher than RIE provide etch rates of 700 Å min −1 for NiFe and NiFeCo in Cl 2/Ar discharges, and >10,000 Å min −1 for NiMnSb in SF 6/Ar. Sub-micron features with smooth, vertical sidewalls are obtained using SiO 2 or SiN X masks. Photoresist is generally found to be an unsuitable mask under high density plasma conditions.