an apparatus and method are described for etching ni - containing films using gas phase plasma etching . etching of ti — ni alloys is carried out by exposure to plasma comprising hydrogen halide and carbonyl etching gases . the ti in the ti — ni alloy is etched via an ion - assisted reaction with hx and the ni is etched by reacting with co . the method is particularly well suited for anisotropic etching of ti — ni metal gates for cmos applications . etching of ni — fe layers is carried out by exposure to plasma comprising a carbonyl etching gas .