Niobium may be used as an electrode and wiring material in Josephson junction technology. For edge coverage of lines patterned in these films, it is critical to produce a controlled, tapered edge profile. Reactive etching is one of the feasible techniques to accomplish this goal. Plasma etching of niobium in a CF4/O2 gas plasma was studied using an anodically coupled parallel plate reactor. The edge angle was found to be dependent mainly on the etching rate ratio (ERR) of the photoresist to the underlying Nb. Factors which affect the etch rates of Nb and photoresist (thus ERR) such as Nb surface area, temperature of the substrate table, and oxygen concentration in CF4 will be discussed. Parametric studies on the effects of total gas flow rate and chamber pressure will also be reported. © 1983, American Vacuum Society. All rights reserved.