Effects of ultraviolet illumination on dry etch rates of NiFe-based magnetic multilayers

NiFe and NiFeCo were dry etched in inductively coupled plasma $Cl2/Ar$ and $CO/NH3$ discharges, either with or without concurrent UV illumination from a Hg arc lamp. No enhancement was observed for $CO/NH3$ etching of the two materials, or for $Cl2/Ar$ etching of NiFe. However, enhancements in etch rate of up to a factor of three were observed for $Cl2/Ar$ etching of NiFeCo when ultraviolet (uv) illumination was employed. The etched surface morphologies were similar both with and without the UV irradiation. The etch rates in $Cl2/Ar$ discharges were strongly correlated with the amount of chlorinated residues detected on the surface by Auger electron spectroscopy, indicating that the desorption of the metal chloride reaction products was the rate-limiting step in the etching.