Wet chemical etching of NiFe, NiFeCo and NiMnSb for magnetic device fabrication

Thin film NiMnSb is found to be wet chemically etched in a range of solutions, including HNO3, H2SO4:H2O2, FeCl3 and HF, with activation energies in the range 10–23 kCal mol−1, i.e. a reaction-limited regime. The degree of sidewall undercut is a function of solution type. Both NiFe and NiFeCo can be etched in H2SO4 and HNO3, with reaction-limited characteristics, while HCl at 25°C is completely selective for NiFe over NiFeCo, even for 7% Co alloys. The degree of sidewall undercut on NiFe is also a strong function of solution type.