Reactive ion etching processes on titanium tungsten thin films have been investigated with CF4/O-2, CF4/Cl-2, and CF4/HCl feed gases. Process parameters such as feed gas composition, radio-frequency power, and pressure showed tremendous effects on the etch rate and the etch selectivity. Both F and Cl are effective etchants for the titanium tungsten film. The etch rate is chemically controlled by the F concentration in the CF4/O-2 plasma, and by the sum of Cl and F concentrations in the CF4/Cl-2 and CF4/HCl plasmas. The etch rate is a function of both the plasma phase etchant concentration and the ion bombardment energy. The peak etch rate was obtained at the medium pressure range, e.g., 100 mTorr, due to the combination of the above two factors. The F residue was detected on the CF4 plasma etched surface, while a trace amount of Cl was detected on the Cl-2 plasma etched surface. Although the plasma-enhanced chemical vapor deposition silicon nitride was etchable with the same type of plasma, an etch selectivity of greater than 2 was achieved under the low ion bombardment condition. (C) 2007 The Electrochemical Society.