Study of W/Ti triode plasma etching

Real microelectronic structures made of W/Ti layers and patterned with a photoresist mask have been etched successively in SF6/N2 and SiCl4/Cl2 plasmas with a triode etching system. The etched samples have been analyzed after different steps of the process with scanning electron microscopy and x-ray photoelectron spectroscopy (XPS). Angular XPS carried out on such structures supplies spatially resolved analysis by the geometrical shadowing effect of specific photoelectrons. The tungsten etching process has been optimized after study of the analysis results with a statistical experimental design. The photoresist fluorination has been spatially characterized by XPS and discussed. At the end of the tungsten etching, TiFx films are observed as trench sidewalls and cannot be removed during titanium etching. By characterization of these films and then by detection of their presence, angular XPS has been successful in developing a new etching process.