Patterning of NiFe and NiFeCo in CO/NH3 high density plasmas

The CO/NH3 plasma chemistry operated under conventional reactive ion etching conditions does not etch NiFe or NiFeCo. However, under high density plasma conditions, etch rates up to ∼500 Å min−1 are obtained for both materials provided optimized ratios of CO:NH3 and values of ion flux and ion energy are employed. The etch mechanism still has a strong physical component and appears to depend on having sufficient CO to form carbonyl etch products, and to avoid formation of a carbide-like surface layer. Under nonoptimized conditions, the latter can lead to net deposition rather than etching.