An improved low-volume gas distribution assembly for a chemical downstream etch tool includes a focusing collar positioned within a process chamber and having a depending shroud in close proximity to a wafer chuck. An apertured gas delivery conduit rests on channels formed in slanted sides of a central tube of the focusing collar. The apertures in the gas delivery conduit are patterned and dimensioned to provide substantially uniform distribution of a process gas over the upper surface of the workpiece. The central tube is sealed with a cover plate and the process chamber is covered with a chamber lid.