Patterning of thin film NiMnSb using inductively coupled plasma etching

Abstract

Several plasma chemistries based on fluorine (SF6, NF3), Cl2/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 μm 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. Cl2/Ar showed a similar trend, with net deposition at low dc 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 (⩾3000 Å min−1) were obtained with BI3/Ar at halide percentages ⩾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 Cl2-based mixtures.