Patterning of thin film NiMnSb using inductively coupled plasma etching

Several plasma chemistries based on fluorine (SF6, NF3), Cl-2/Ar, BI3/Ar, or BBr3/Ar were compared for etching NiMnSb under inductively coupled plasma (ICP) conditions. ICP source power, radio frequency chuck power, and plasma composition were found to have strong effects on the etch rate. SF6/Ar discharges provided the fastest etch rates for NiMnSb (>1 mu m min(-1)) even with small amounts of source power (100 W) addition. On the other hand, NF3/Ar showed net deposition rather than etching at source powers >100 W or at high NF3 percentages. Cl-2/Ar showed a similar trend, with net deposition at low de self-bias (-100 V), but net etching above this threshold. BBr3/Ar discharges produced deposition under all the conditions investigated while relatively high etch rates (greater than or equal to 3000 Angstrom min(-1)) were obtained with BI3/Ar at halide percentages greater than or equal to 70%. In terms of etched surface morphology, SF6/Ar provided the best surfaces, with root-mean-square roughness of 2.5 nm and vertical etched profiles. Surfaces etched in plasma chemistries other than SF6/Ar revealed Mn enrichment, an indication of involatile Mn etch products. The SF6 chemistry has the further advantage of the absence of the corrosion noted with Cl-2-based mixtures. (C) 1998 American Vacuum Society. [S0734-211X(98)07906-2].