Titanium nitride (TiN) is widely used in metal gate applications. Exposing TiN to a Cl-2/HBr plasma results in pronounced surface roughness that can be easily characterized by ellipsometry. The ellipsometric angle Delta is proportional to the roughness if the roughness does not exceed 30 nm. It is possible to plot a "roughness diagram" where a border can be drawn between the smooth and rough etch surfaces depending on the etch conditions. This diagram could be used for gate-etch process optimization. In our case, the roughness could be overcome by increasing HBr content and/or substrate bias during the etching. (c) 2007 The Electrochemical Society.