DRY AND WET ETCH PROCESSES FOR NIMNSB HEUSLER ALLOY THIN-FILMS

A variety of plasma etching chemistries were examined for patterning N iMnSb Heusler alloy thin films and associated Al2O3 barrier layers. Ch emistries based on SF6, Cl-2, and BCl3 were all found to provide faste r etch rates than pure Ar sputtering. In all cases the etch rates were strongly dependent on both the ion flux and ion energy. Selectivities of greater than or equal to 20 for NiMnSb over Al2O3 were obtained in SF6-based discharges, while selectivities less than or equal to 5 wer e typical in Cl-2, BCl3, and CH4/H-2 plasma chemistries. Wet etch solu tions of HF/H2O and HNO3/H2SO4/H2O were found to provide reaction-limi ted etching of NiMnSb that was either nonselective or selective, respe ctively, to Al2O3.