Results of the study of reactive ion etching of tungsten, tungsten nitride, and silicon in gas mixtures are presented. For plasma diagnostics, optical emission spectroscopy (actinometry) was used. Using the actinometry technique, it was possible to show that etching mechanisms were different for Si-F and WF chemistries. Anisotropic etching of tungsten/tungsten nitride using conventional reactive ion etcher has been obtained, and conditions of achieving anisotropic etching have been analyzed. A correlation is found between anisotropy of tungsten etching and the ratio of Si/W etch rates. Mechanisms of fluorine redistribution between the bottom/sidewall surfaces due to surface diffusion and/or reflection are proposed as possible reasons for the observed correlation.© 2002 The Electrochemical Society. All rights reserved.