Inductively coupled plasma etching of NiFe and NiFeCo

The etch yield and rates of Ni0.8Fe0.2 and Ni0.8Fe0.13Co0.07 in ICP Cl-2-based plasma has been measured as a function of both ion nux and ion energy. At low ion energies less than or equal to 100eV, the etch rates peak at 700 Angstrom.min(-1) for Cl-2/Ar plasma chemistry, with somewhat lower rates (similar to 400 Angstrom.min(-1)) for N-2 or H-2 addition. The etch mechanism is formation of NiClx, FeClx and CoClx species, which are desorbed by ion-assistance. If the ion-to-neutral ratio is not optimized then the etching reverts to either a pure sputtering regime, or to net deposition through formation of a thick chlorinated selvedge layer on both NiFe and NiFeCo. Under ICP conditions other materials comprising a GMR stack, including Cu, TaN and CrSi, can also be etched. Each selectivities over SiO2 and SiNx masks are low and are typically under unity.